Raphaël Pik

@article{Bekaert_etal2023,

title = {Last glacial maximum cooling of 9 textdegreeC in continental Europe from a 40 kyr-long noble gas paleothermometry record},

author = {D. V. Bekaert and P. H. Blard and Y. Raoult and R. Pik and R. Kipfer and A. M. Seltzer and E. Legrain and B. Marty},

doi = {10.1016/j.quascirev.2023.108123},

year  = {2023},

date = {2023-01-01},

journal = {Quaternary Science Reviews},

volume = {310},

pages = {108123},

abstract = {The Last Glacial Maximum (LGM; \^{a}`u26--18 kyr ago) is a time interval of great climatic interest characterized by substantial global cooling driven by radiative forcings and feedbacks associated with orbital changes, lower atmospheric CO2, and large ice sheets. However, reliable proxies of continental paleotemperatures are scarce and often qualitative, which has limited our understanding of the spatial structure of past climate changes. Here, we present a quantitative noble gas temperature (NGT) record of the last \^{a}`u40 kyr from the Albian aquifer in Eastern Paris Basin (France, \^{a}`u48textdegreeN). Our NGT data indicate that the mean annual surface temperature was \^{a}`u5 textdegreeC during the Marine Isotope Stage 3 (MIS3; \^{a}`u40--30 kyr ago), before cooling to \^{a}`u2 textdegreeC during the LGM, and warming to \^{a}`u11 textdegreeC in the Holocene, which closely matches modern ground surface temperatures in Eastern France. Combined with water stable isotope analyses, NGT data indicate $delta$D/NGT and $delta$18O/NGT transfer functions of +1.6 textpm 0.4texttenthousand/textdegreeC and +0.18 textpm 0.04texttenthousand/textdegreeC, respectively. Our noble-gas derived LGM cooling of \^{a}`u9 textdegreeC (relative to the Holocene) is consistent with previous studies of noble gas paleothermometry in European groundwaters but larger than the low-to-mid latitude estimate of 5.8 textpm 0.6 textdegreeC derived from a compilation of noble gas records, which supports the notion that continental LGM cooling was more extreme at higher latitudes. While an LGM cooling of \^{a}`u9 textdegreeC in Eastern France appears compatible with recent data assimilation studies, this value is greater than most estimates from current-generation climate model simulations of the LGM. Comparing our estimate for the temperature in Eastern France during MIS3 (6.4 textpm 0.5 textdegreeC) with GCM outputs presents a promising avenue to further evaluate climate model simulations and constrain European climate evolution over the last glacial cycle.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ayalew_etal2020,

title = {Pedogenic origin of Mezezo opal hosted in Ethiopian Miocene rhyolites},

author = {D. Ayalew and R. Pik and S. Gibson and G. Yirgu and S. Ali and D. Assefa},

doi = {10.3749/canmin.1900059},

year  = {2020},

date = {2020-01-01},

journal = {The Canadian Mineralogist},

volume = {58},

pages = {231--246},

abstract = {Opals are widespread within Miocene volcanic sequences in the North Shoa province of Central Ethiopia. The opal occurs as cavity fillings in a 5 m thick seam of glassy rhyolitic ignimbrite that is sandwiched between basaltic lava flows. The opals occur over a large area (.25 km2). X-ray diffraction analyses show that they are CT-type. The opals contain lower concentrations of trace elements (up to 100 times) than the host rhyolite. Ratios of most trace elements are, however, similar in both the opals and rhyolites. The opals have high d18O values (28.4--33.8%) that imply a low temperature of formation, between 20.55 and 25.74 8C. We therefore propose that the opals precipitated from meteoric waters that had percolated through and interacted with the host rhyolite. Field evidence indicates that this weathering and alteration occurred immediately after emplacement of the rhyolites, but prior to the extrusion of the overlying basalt flows.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Charreau_etal2020,

title = {A 6 Ma record of palaeodenudation in the central Himalayas from in situ cosmogenic 10 Be in the Surai section},

author = {J. Charreau and J. Lav\'{e} and C. France-Lanord and N. Puchol and P. H. Blard and R. Pik and A. P. Gajurel and ASTER Team.},

doi = {10.1111/bre.12511},

year  = {2020},

date = {2020-01-01},

journal = {Basin Research},

pages = {1--22},

abstract = {To better constrain late Neogene denudation of the Himalayas, we analysed in situ 10Be concentrations in 17 Neogene sediment samples of the Surai section (central Nepal) and two modern sediment samples of the Rapti River. We first refined the depositional ages of the Surai section from 36 new paleomagnetic analyses, five 26Al/10Be burial ages, and, based on the Dynamic Time Warping algorithm, 104 automatically calculated likely magnetostratigraphic correlations. We also traced changing sediment sources using major element and Sr-Nd isotopic data, finding at 4--3Ma a switch from a large, trans-Himalayan river to a river draining only the Lesser Himalaya and Siwalik piedmont, increasing the contribution of recycled sediments at that time. 10Be concentrations in Neogene sediments range from (1.00 textpm0.36) to (5.22textpm0.98)texttimes103 at g--1 and decrease with stratigraphic age. Based on a flood plain transport model, our refined age model, and assuming a drainage change at 4--3Ma, we reconstructed 10Be concentrations at the time of deposition. Assuming cosmogenic production rates similar to those of the modern basins, we calculated palaeodenudation rates of 0.9textpm0.5 to 3.9textpm2.7mm a --1 from ca. 6 to 3Ma in the palaeo-Karnali basin and 0.6textpm0.2 to 1.6textpm0.8mm a --1 since ca. 3Ma in the palaeo-Rapti basin. Given the uncertainties and similar modern values of 2mm a--1, the palaeo-Karnali denudation rates may have been steady at 1.7textpm0.3mm a--1 for the last ca. 6Ma. A transient acceleration of the denudation in the palaeo-Rapti basin of 1.5mm a--1 since ca. 1.5Ma was likely due to the reworking of older, 10Be-depleted Siwalik sediments in the foreland. If true, this steadiness of the denudation rates may suggest that Quaternary glaciations did not largely affect Himalayan denudation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Litty_etal2020,

title = {Spatial variability of Quaternary denudation rates across a volcanic ocean island (Santo Ant~ao, Cape Verde) from cosmogenic 3He},

author = {C. Litty and J. Charreau and P. H. Blard and R. Pik and S. Nomade},

doi = {10.1016/j.geomorph.2020.107557},

year  = {2020},

date = {2020-01-01},

journal = {Geomorphology},

volume = {375},

pages = {107557},

abstract = {Denudation of volcanic ocean islands creates remarkable landscapes and contributes to Earthtextquoterights carbon cycle, since the chemical alteration of basalts is a CO2 sink. Because many volcanic islands have large climate gradients and relatively lowvariations in lithology and tectonic history, they represent excellent natural laboratories for studying climatic effects on landscape evolution. However, little is known about the control of denudation rates in ocean islands and the respective influences of climatic gradients andmorphological parameters. Here,we present new measurements of long-term denudation rates from Santo Ant~ao Island, Cape Verde (17textdegreeN). In this 779 km2 island, mean annual precipitation ranges from 40 mmtextperiodcenteredyr−1 in the southwest to 1100 mmtextperiodcenteredyr−1 in the north. To constrain the spatial distribution of denudation rates, we measured the cosmogenic 3He concentration in river transported pyroxene grains from 23 river bedload samples. We obtained basin wide denudation rates ranging from 2.7textpm0.1 to 57.5textpm0.3 m/Ma. The denudation rates display a significant spatial variability, with the highest rates in catchments located in the northeast side of the island where modern precipitation are the highest and lowdenudation rates in the southern andwestern dry basins. Our study shows that precipitation is themain control on denudation and landscape development of the Santo Ant~ao volcanic island. This study provides for the first time the spatial distribution of denudation rates across a volcanic island located in a tropical zone.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bastian_etal2019,

title = {Chemical erosion rates in the upper Blue Nile Basin and related atmospheric CO2 consumption},

author = {L. Bastian and N. Vigier and M. Revel and G. Yirgu and D. Ayalew and R. Pik},

doi = {10.1016/j.chemgeo.2019.03.033},

year  = {2019},

date = {2019-01-01},

journal = {Chemical Geology},

volume = {518},

pages = {19--31},

abstract = {Silicate weathering of basaltic rocks constitutes a non-negligible sink of atmospheric CO2 but the role it plays in the regulation of past and future global climate is still matter of debate. In this study, silicate weathering rates for various sub-basins of the Ethiopian Traps, emplaced 30 million years ago, and the corresponding atmospheric CO2 consumption rates are evaluated. For this, major and trace elements were measured in the dissolved phases and in the sedimentary particles carried and deposited by the main rivers flowing through this steep region. Lithium isotopes and major elements were also measured in the extracted clay fractions in order to infer complementary information on weathering processes in this region. Clay $delta$7Li values correlate positively with Mg/Ti ratios, and are best explained by varying ratios of leaching versus clay formation rate.Although located in a region annually submitted to monsoon, average silicate weathering rate (16.1 tons/km2/year) and CO2 consumption rate (0.65 texttimes 1012 mol/year) are estimated to be low when compared to other basaltic regions such as the Deccan Traps, and volcanically active islands of the tropical zone. This is surprising since the concentrations of Total Dissolved Solids of the Ethiopian rivers are among the highest ones. With a 2D rainfall model that takes into account the detailed topography of the region, annual occurrence of the Monsoon, and monitoring station data, we show that runoff intensity is a key parameter that explains this difference. We determine that, at present, the weathering of the Ethiopian Traps plays a negligible role in the carbon cycle. However, simple calculations, which integrate recent knowledge on African climate variations and on weathering controls, illustrate that during the African Humid Period (14--8 kyr), a significant increase of Monsoon precipitation may have resulted in much higher weathering rates and related CO2 consumption (0.91--1.5 texttimes 1012 mol/year). This study therefore evidences the potential importance of this region in the past, and the need to quantify more precisely the variations of the monsoon intensity and its impact on tropical watersheds for reconstructing past CO2 levels.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bellahsen_etal2019,

title = {Shortening of the axial zone, Pyrenees : Shortening sequence,upper crustal mylonites and crustal strength},

author = {N. Bellahsen and L. Bayet and Y. Denele and M. Waldner and L. Airaghi and C. Rosenberg and B. Dubacq and F. Mouthereau and M. Bernet and R. Pik and A. Lahfid and A. Vacherat},

doi = {10.1016/j.tecto.2019.06.002},

year  = {2019},

date = {2019-01-01},

journal = {Tectonophysics},

volume = {766},

pages = {433--452},

abstract = {The strength of the lithosphere may be constrained qualitatively by field observations on localized vs distributed modes of deformation and by the mineral assemblages formed during deformation. The internal deformation of the Bielsa basement unit of the Pyrenean Axial zone is investigated through structural, microstructural and thermometric data. In this area, shortening is widely distributed as attested by the folded attitude of the interface between the basement and its sedimentary Triassic cover. Shortening is estimated around 1.7 km (13%) from a regional balanced cross-section and should be considered in pre-Pyrenean reconstructions. Shortening probably occurred before strain localization on crustal ramps as suggested by zircon fission-track analysis. Distributed shortening is characterized at small-scale by low-temperature mylonites and cataclasites. In thin-section, feldspar originally present in the magmatic protolith is partially to totally sericitized. This transformation led to significant weakening of the rock and took place in the 250--350 textdegreeC temperature range. Sericitization is ubiquitous, even in un-deformed granodiorites. This shows that the weakening effect of sericitization not only occurs in ultra-mylonites, ultra-cataclasites and phyllonites but also more generally in the upper crust early during the shortening history, with implications for the shortening style. Estimates of the geothermal gradient suggest that inherited thermicity may also have influenced the style of shortening. We propose that the upper crust was very weak before or at the onset of its shortening due to high-thermal gradients and fluid circulation that induced large-scale sericitization in greenschist facies conditions. This has strong implications on the rheological evolution of the upper crust submitted to metamorphic alteration in the greenschist facies and below.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{DeFelipe_etal2019,

title = {Unraveling the Mesozoic and Cenozoic Tectonothermal Evolution of the Eastern Basque‐Cantabrian Zone--Western Pyrenees by Low‐Temperature Thermochronology},

author = {I. DeFelipe and D. Pedreira and J. A. Pulgar and P. Van der Beek and M. Bernet and R. Pik},

doi = {10.1029/2019TC005532},

year  = {2019},

date = {2019-01-01},

journal = {Tectonics},

volume = {38},

number = {9},

pages = {3436--3461},

abstract = {Low‐temperature thermochronology studies have increased our knowledge of the orogenicprocesses along the Pyrenean‐Cantabrian mountain belt by placing time constraints on the exhumationhistory of its rocks. However, a significant gap in the data existed between the western Pyrenees and thecentral Cantabrian Mountains, hampering a comprehensive view of the tectonothermal evolution along thebelt. We present a new apatitefission track and zircon (U‐Th)/He (ZHe) data set for the easternBasque‐Cantabrian zone--western Pyrenees. Apatitefission track central ages cluster in theEocene‐Oligocene. ZHe samples can be separated into two groups : Group 1 depicts clustered ZHe ages‐eUconcentration (Cinco Villas massif) and Group 2 depicts dispersed ZHe ages‐eU concentration (Alduidesmassif and a Paleozoic rock pinned along the Leiza thrust). A sample from the Oroz‐Betelu massif showsintermediate behavior. Inverse modeling suggests that samples from Group 1 reached 240--280 textdegreeC in theLate Cretaceous, implying deep sedimentary burial of the Cinco Villas massif before its major exhumationphase, most probably in the early to middle Eocene, postdating the phase of rapid exhumation of thewestern part of the Leiza thrust. The sample from the Oroz‐Betelu massif, far from the Mesozoic exhumedmantle domain, experienced maximum temperatures close to 200 textdegreeC by burial beneath the Jaca‐Pamplonabasin. It was later exhumed in the hanging wall of the Gavarnie thrust in the Bartonian‐Priabonian. Thiswork provides new insights into the tectonothermal evolution of the Basque massifs and the inversion of ahyperextended margin.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Deng_etal2019,

title = {Titanium isotopes as a tracer for the plume or island arc affinity of felsic rocks},

author = {Z. Deng and M. Chaussidon and P. Savage and F. Robert and R. Pik and F. Moynier},

doi = {10.1073/pnas.1809164116},

year  = {2019},

date = {2019-01-01},

journal = {Proceedings of the National Academy of Sciences of the United States of America},

volume = {116},

number = {4},

pages = {1132--1135},

abstract = {Indirect evidence for the presence of a felsic continental crust, such as the elevated 49Ti/47Ti ratios in Archean shales, has been used to argue for ongoing subduction at that time and therefore plate tectonics. However, rocks of intermediate to felsic compositions can be produced in both plume and island arc settings. The fact that Ti behaves differently during magma differentiation in these two geological settings might result in contrasting isotopic signatures. Here, we demonstrate that, at a given SiO2 content, evolved plume rocks (tholeiitic) are more isotopically fractionated in Ti than differentiated island arc rocks (mainly calc-alkaline). We also show that the erosion of crustal rocks from whether plumes (mafic in average) or island arcs (intermediate in average) can all produce sediments having quite constant 49Ti/47Ti ratios being 0.1--0.3 per mille heavier than that of the mantle. This suggests that Ti isotopes are not a direct tracer for the SiO2 contents of crustal rocks. Ti isotopes in crustal sediments are still a potential proxy to identify the geodynamical settings for the formation of the crust but only if combined with additional SiO2 information.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gautheron_etal2019,

title = {A multi-method, multi-scale theoretical study of He and Ne diffusion in zircon},

author = {C. Gautheron and D. Mbongo Djimbi and J. Roques and H. Balout and R. A. Ketcham and E. Simoni and R. Pik and A. M. Seydoux-Guillaume and L. Tassan-Got},

doi = {10.1016/j.gca.2019.10.007},

year  = {2019},

date = {2019-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {268},

pages = {348--367},

abstract = {The quantification of He and Ne diffusion behavior in crystals rich in U and Th such as zircon is key for the interpretationof (U-Th)/4He and (U-Th)/21Ne thermochronometric ages. Multiple parameters such as chemical substitution, channelobstruction and damage can modify the diffusivity compared to a pristine structure. To investigate the impact of these param-eters, we have conducted a theoretical diffusion study combining a series of methods and approaches to address the problemacross the necessary range of scales (atomic to crystal size). First, using quantum calculation, we determine the different Heand Ne insertion sites, insertion energies and diffusion pathways at the atomic scale for an ideal pristine zircon structure (i.e.damage free). These results serve as input for a 3D random walk simulation of atomic trajectories that provides diffusion coef-ficients for damage-free zircon crystals. Second, as natural zircon crystals are not perfect, we model the impact of differenttypes of damage and diffusion pathway obstruction at the atomic level on He and Ne diffusion in 3D. The calculated Heand Ne diffusion coefficients for pure ZrSiO4exhibit strongly anisotropic behavior and very high diffusivity along thec-axis, and with 3D, closure temperatures of-197textdegreeC and-202textdegreeC respectively. The results for He are comparable to previousDFT studies but strongly different from experimental diffusion results; results for Ne are similar in this respect. Modelling theimpact of different types of damage (vacancies, recoil, fission, voids or fluid inclusions) and obstruction on He and Ne diffu-sion reveals important implications for the (U-Th)/He and (U-Th)/Ne thermochronometers. First, obstruction alone does notsignificantly modify He and Ne diffusion except to reduce anisotropy. Second, trapping is the primary mechanism altering Heand Ne diffusion even at low dose, and we predict the maximal trapping energies for He and Ne to be 164 and 320 kJ/mol,similar to values inferred from experimental data. We also propose that the closure temperature increases non-linearly withdamage, with effective trapping energy increasing with dose until a threshold, possibly corresponding to a percolationtransition, after which retentivity decreases. Based on field data sets we also anticipate a value for this threshold of around-2--5-1017a/g, lower than previously proposed. We show Ne to be highly blocked by damage and predict similar diffusion behavior to He, but with higher retentivity. We demonstrate the importance of investigating rare gas diffusion at the atomiclevel for comparison with experimental data, in order to build a predictive diffusion law at different scales.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ternois_etal2019,

title = {Thermochronological evidence of early orogenesis,Eastern Pyrenees, France},

author = {S. Ternois and M. Odlum and M. Ford and R. Pik and D. Stockli and B. Tibari and A. Vacherat and V. Bernard},

doi = {10.1029/2018TC005254},

year  = {2019},

date = {2019-01-01},

journal = {Tectonics},

volume = {38},

pages = {1308--1336},

abstract = {The Pyrenean orogen was generated from late Santonian--early Campanian to middle Miocene by N‐S con-vergence of the Iberian and European plates (Choukroune, 1989 ; Mu~noz, 1992 ; Macchiavelli et al., 2017).External orogenic zones and foreland basins record two distinct periods of low but accelerating tectonicshortening and subsidence, latest Santonian--Danian and Thanetian--Oligocene, separated by a quiet (verylow to near‐zero subsidence) period during the Paleocene (Ford et al., 2016). These two periods arerecognized to be synorogenic and mark two phases of convergence, the second generally recorded asEocene--Oligocene in low‐temperature thermochronology studies. Significantly, the orogentextquoterights three‐phaseconvergence history does not correspond to behavior predicted by foreland dynamic models (Naylor \&Sinclair, 2008 ; Sinclair et al., 2005 ; Sinclair \& Naylor, 2012). While the evolution of crustal thickening, ther-micity, orogen relief, and erosion during the main Eocene--Oligocene collisional phase are well studied andshow a clear link to foreland basin dynamics (Fillon et al., 2013 ; Sinclair, 2011), the early Pyrenean history ofconvergence and the subsequent phase of quiescence are poorly constrained. In particular, there are few dataon the thermal and dynamic behavior of the orogen during the earliest phase of Pyrenean convergence. Therecord of early orogenesis is best observed in the retrowedge where shortening and translation values are low(Naylor \& Sinclair, 2008) and where the main Aptian--Cenomanian rifting phase is preserved. In this paperwe present new zircon and apatite (U‐Th‐Sm)/He (ZHe and AHe, respectively) data from an externalPaleozoic crustal block, Agly‐Salvezines (Figures 1 and 2), in the eastern Pyrenean retrowedge. By integrat-ing these data with new and published geological data, we address the following questions : Can we recog-nize a thermal signature for the onset of Pyrenean convergence and for Paleocene quiescence ? Are earlycrustal thermal events contemporaneous with early foreland tectonic events, or is there a lag time betweenthese two phenomena ? Can we distinguish an early orogenic thermal signature from other thermal eventssuch as those associated with preceding rifting or later collision ?},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ayalew_etal2019,

title = {Differential fractionation of rhyolites during the course of crustal extension, Western Afar (Ethiopian Rift)},

author = {D. Ayalew and R. Pik and N. Bellahsen and L. France and G. Yirgu},

doi = {10.1029/2018GC007446},

year  = {2019},

date = {2019-01-01},

urldate = {2018-01-01},

journal = {Geochemistry, Geophysics, Geosystems G3},

volume = {20},

number = {2},

pages = {571--593},

abstract = {We report field observation, age, chemical (major and trace elements), and isotope (Sr‐Nd‐Pb) data for felsic volcanic rocks from Central Afar and adjacent western margin. Investigated volcanic rocks are dominantly rhyolites with minor trachytes, and they are geochemically similar. Their ages range from textasciitilde30 Ma (prerift stage), textasciitilde20 Ma (early synrift), textasciitilde8--4 Ma (main thinning event) to textasciitilde2.5--0.1 Ma (late synrift/continental breakup), representing the entire volcanic‐tectonic events that occurred episodically. Major element variations are consistent with fractionation of gabbroic cumulates. Trace element and isotope data preclude an origin by crustal anatexis; the rhyolites are rather genetically linked to the associated basalts and variously contaminated by the crust during differentiation of magmas. Chemical and isotopic data of the rhyolites support an origin by open system differentiation at deep crustal levels (hot wall rock and high r = rate of assimilation/rate of crystallization) and shallow crustal levels (cold wall rock and low r) with a change in the composition of the assimilated material from lower crustal to upper crustal type. Assimilation appears to decrease in recent times with Quaternary rhyolites, emplaced nearby the active magmatic segments in Afar, which exhibit the isotopic compositions closest to original mantle signature. This is compatible with a crust below the active magmatic segments resulting from important addition of juvenile basic magmas. Such results and interpretations provide actual constrains to suggest that the present‐day stage is probably very close to continental breakup, which will be achieved once the continental crust will be entirely replaced by new magmatic crust.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jolivet_etal2018_2,

title = {Extensional crustal tectonics and crust-mantle coupling, a view from the geological record},

author = {L. Jolivet and A. Menant and C. Clerc and P. Sternai and N. Bellahsen and S. Leroy and R. Pik and M. Stab and C. Faccenna and C. Gorini},

doi = {10.1016/j.earscirev.2018.09.010},

year  = {2018},

date = {2018-01-01},

journal = {Earth-Science Reviews},

volume = {185},

pages = {1187--1209},

abstract = {We present here a number of geological observations in extensional contexts, either continental rifts or back-arcs, that show different situations of potential coupling between asthenospheric flow and crustal deformation. Several of these examples show a deformation distributed over hectometre to kilometre thick shear zones, accommodated by shallow dipping shear zones with a constant asymmetry over large distances. This is the case of the Mediterranean back-arc basins, such as the Aegean Sea, the northern Tyrrhenian Sea, the Alboran domain or the Gulf of Lion passive margin. Similar types of observation can be made on some of the South Atlantic volcanic passive margins and the Afar region, which were formed above a mantle plume. In all these examples the lithosphere is hot and the lithospheric mantle thin or possibly absent. We discuss these contexts and the main controlling parameters for this asymmetrical distributed deformation that implies a simple shear component at the scale of the lithosphere. These parameters include an original heterogeneity of the crust and lithosphere (tectonic heritage), lateral density gradients and contribution of the underlying asthenospheric flow through basal drag or basal push. We discuss the relations between the observed asymmetry and the direction and sense of the mantle flow underneath. The chosen examples suggest that two main mechanisms can explain the observed asymmetry: (1) shearing parallel to the Moho in the necking zone during rifting and (2) viscous coupling of asthenospheric flow and crustal deformation in back-arc basins and above plumes. Slipping along pre-existing heterogeneities seems a second-order phenomenon at lithospheric or crustal scale.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{LeGall_etal2018,

title = {The Red Beds series in the Erta Ale segment, North Afar. Evidence for a 6 Ma-old post-rift basin prior to continental rupturing},

author = {B. Le Gall and S. Leleu and R. Pik and F. Jourdan and G. Chazot and D. Ayalew and G. Yirgu and C. Cloquet and F. Chauvet},

doi = {10.1016/j.tecto.2018.10.002},

year  = {2018},

date = {2018-01-01},

journal = {Tectonophysics},

volume = {747-748},

pages = {373--389},

abstract = {The Erta Ale rift segment, North Afar, is regarded as the most mature rift part within the entire Afar rift system. Very little is known about its deformation history because of limited exposures of geological records in its innerfloor, except volcanics of the Erta Ale chain, and the poorly-known Red Beds series along the flanks of the depression. An integrated study, combining sedimentological, geochemical, 40Ar-39 Ar radiometric and tectonic approaches, has been devoted to Red Beds series fl anking the depression to the SW. Our new results allow to argue that (1) the \> 300 m-thick Red Beds exposed section comprises alluvial deposits that enclose (2) basaltic lavas and related sill intrusions that both yield 6 Ma 40Ar-39Ar ages and display similar geochemical affinities, (3) the Red Beds series locally overlap unconformably basement bounding terrains, and (4) are involved in a limited number of low-displacement normal faults that recorded a modest amount of extension (\< 6%), (5) isotope contents of Red Beds volcanics indicate crustal contamination, without any contribution of the Afar plume, by contrast to the younger Erta Ale magmatism which represents the more recent Afar-plume related event in the Erta Ale segment. Combining these results leads us to regard the Red Beds series as part of an alluvial basin that post-dated a major rift event to which are attributed to (1) the present-day Ethiopian fault-scarp, (2) a concealed sedimentary depocenter at depth in its hanging wall, and (3) prominent crustal thinning. Riftward migration and axial focusing of strain during Miocene-Present times is also argued, while later flexuring of the entire Red Beds basin is assigned to magmatic loading during the axial emplacement of the Erta Ale volcanic chain. Lastly, emphasis is put on the large-scale segmentation of the Afar system into the tectonically-accreted Erta Ale rift segment to the north, and the magmatically-accreted Central segment to the south.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Liu-Zeng_etal2018,

title = {Multiple episodes of fast exhumation since Cretaceous in southeast Tibet, revealed by low-temperature thermochronology},

author = {J. Liu-Zeng and J. Zhang and D. McPhillips and P. Reiners and W. Wang and R. Pik and L. Zeng and G. Hoke and K. Xie and P. Xiao and D. Zheng and Y. Ge},

doi = {10.1016/j.epsl.2018.03.011},

year  = {2018},

date = {2018-01-01},

journal = {Earth and Planetary Science Letters},

volume = {490},

pages = {62--76},

abstract = {The southeast margin of the Tibetan plateau is characterized by deeply incised river valleys separated by a perched low relief landscape that gently descends from the high Tibetan plateau towards the southeast. When and how this unique landscape formed is debated. The onset of increased river incision is often interpreted as a proxy for the timing of surface uplift. Here, apatite and zircon (U--Th)/He and apatite fission track thermochronometries are employed to map the spatial and temporal pattern of exhumation in the region. Vertical profiles of granitic rocks were collected near Deqin (�`u28.5textdegreeN) and Weixi (�`u27.5textdegreeN). The two transects share a similar exhumation history, with two episodes of relatively fast exhumation (�`u100--300 m/Myr) in the Cenozoic : during the Paleocene to Eocene (60--40 Ma) and Miocene to present (20--0 Ma), separated by an intervening period of slow exhumation. A pulse of moderate to high exhumation (70--300 m/Myr) during the mid- to late-Cretaceous (120--80 Ma) is also present in the data. However, the rate and total amount of exhumation near Deqin is larger than at Weixi and is especially pronounced in the interval between 20 Ma to present. We interpret this difference as possibly related to differences in erosion rates between the Lancang (Deqin) and the Jinsha (Weixi) rivers. The Paleocene to Eocene episode of fast exhumation is likely in response to early Cenozoic deformation along tectonic boundary structures, related to the transpressional collision of the Indian plate with this region. Pre-Miocene episodes of fast exhumation corroborate recent paleoaltimetric studies, which show that the southeast margin of the Tibetan plateau was elevated prior to the Oligocene.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Montel_etal2018,

title = {The giant monazite crystals from Manangotry (Madagascar)},

author = {J. M. Montel and D. Razafimahatratra and P. Perseval and F. Poitrasson and B. Moine and A. M. Seydoux-Guillaume and R. Pik and N. Arnaud and F. Gibert},

doi = {10.1016/j.chemgeo.2017.10.034},

year  = {2018},

date = {2018-01-01},

journal = {Chemical Geology},

volume = {484},

pages = {36--50},

abstract = {The Manangotry area in the South-East of Madagascar is famous for its giant monazite crystals. The studied occurrence is an outcrop near the Manangotry pass, were giant, cm-sized crystals have been found. The crystals are embedded in biotitite levels, also containing cm-sized xenomorphic ilmenite, and are associated with a 1 m thick layer of apatite. Besides giant crystals, monazite is also present as abundant small (mm-sized) grains. The surrounding rocks are leucogranites and charnockites. The monazite giant crystals are chemically homogeneous and thorium-rich, whereas small crystals tend to be heterogeneous. Both biotite and apatite are F-rich. Temperature estimates from biotite and apatite yielded 750 to 800 textdegreeC. Despite their high radioactivity, the giant crystals preserve a high degree of crystallinity. Electron microprobe U-Th-Pb dating produced ages of 537 textpm 14, 534 textpm 10 and 530 textpm 10 Ma, considered to be the age of the main monazite crystallization episode but some minor domains in small grains yielded 482 textpm 12 Ma. The enclosing biotites yielded 453 textpm 6 Ma Ar-Ar ages. More than 98 % of radiogenic helium have been retained in the studied monazite samples, and kinetic experiments indicates the intrinsic diffusion parameters for high-temperature to be Ea= 53 kcal/mol and D0= 3085 cm 2/s. The paragenesis (monazite-apatite-ilmenite-biotite) is different from any other occurrences of larges monazite elsewhere. Based on the current data and literature, the preferred genetic model for these giant monazites is crystallization from a high-temperature fluorine-rich fluid, possibly originating from surrounding charnockites.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Tadesse_etal2018,

title = {Magmatic evolution of the Boku Volcanic Complex, Main Ethiopian Rift},

author = {A. Z. Tadesse and D. Ayalew and R. Pik and G. Yirgu and K. Fontijn},

doi = {10.1016/j.jafrearsci.2018.08.003},

year  = {2018},

date = {2018-01-01},

journal = {Journal of African Earth Sciences},

volume = {149},

pages = {109--130},

abstract = {The Boku volcanic complex is a Quaternary center situated on the axial segment of the Main Ethiopian Rift (MER), located 92 km South-east from Addis Ababa. The main objective of this study is to understand the magmatic evolution of the volcanic complex and to develop a model to answer some outstanding questions related to bimodal products of rift related volcanism, using geological mapping, petrographic and geochemical approaches. The Boku complex is characterized by two main phases of activity : pre-caldera/caldera forming eruptive activity and post-caldera eruptive activity. The volcanic stratigraphy consists from bottom to top of a sequence of rhyolitic lava flows, pumice flows, welded ignimbrite, pumice fall, rhyolitic lava dome, obsidian flow, lower basaltic lava flow, ash flow, basaltic scoria and upper basaltic lava flows. The lithologic varieties together with the geochemical results indicate that the Boku eruptive products are bimodal in composition ; no intermediate compositions are found. The mafic rocks are transitional to weakly subalkaline basalts while the silicic rocks are predominantly peralkaline rhyolites. These two groups of rocks are co-genetic and related to each other by fractional crystallization processes starting from mantle-derived basaltic magma with a small component of crustal contamination. The available geophysical, geochemical and field data suggest that the evolution of the evolved silicic center which hosts a bimodal rock distribution can be explained as a result of prolonged stagnation of transitional basaltic melt (sourced from the mantle) at relatively high pressures, where these evolve to intermediate compositions. The transitional basaltic melts can occasionally erupt to the surface along weakness lines such as faults that infrequently cut the lower part of the shallow reservoir, generating basalts from the intra-caldera and lateral eruptive centers. We consider the intermediate magma is mechanically trapped at mid-crustal depths because of its higher crystal load (ca. 50%). Silicic magma is formed at shallow depth by prolonged fractional crystallization of the intermediate magma and minor assimilation of crustal material. These silicic magmas generate both effusive and explosive eruption products in the overall stratigraphy of the volcanic complex},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Puchol_etal2017,

title = {Variability of magmatic and cosmogenic 3 He in Ethiopian river sands of detrital pyroxenes: Impact on denudation rate determinations},

author = {N. Puchol and P. H. Blard and R. Pik and B. Tibari and J. Lav\'{e}},

doi = {0.1016/j.chemgeo.2016.10.033},

year  = {2017},

date = {2017-01-01},

journal = {Chemical Geology},

volume = {448},

pages = {13--25},

abstract = {In-situ cosmogenic 3He is a robust tool for determining denudation rates or exposure ages of lavas bearing mafic phenocrysts. However, analyses are often complicated by the presence of several helium sources. In particular, in old magmatic rocks with high radiogenic 4He contents, discriminating cosmogenic 3He from magmatic 3He is not straightforward since these varieties may vary largely between aliquots. We sampled sands from the Tekeze and Mile rivers, both draining the basaltic Ethiopian highlands, an area where erosion patterns are intimately linked to the development of the Western Afar margin and to heterogeneous monsoon precipitation. From each river we analyzed textasciitilde15 aliquots of pyroxenes having variable grain sizes (0.3 mm up to N 1 mm). The total 3 He is both higher and more scattered in the bigger grains. Crushing of these largest grains and subsequent melting of the powder tends to produce more homogeneous 3 He values, suggesting that magmatic 3He hosted in inclusions is responsible for most of the inter-aliquot variability. We also performed a Monte Carlo simulation based on a numerical denudation model of the two watersheds. The simulation confirms that cosmogenic3 He variability cannot be responsible for the observed scatter since the cosmogenic 3 He variability is averaged away and unobservable in aliquots of textasciitilde200 grains. A compilation of previously published data also indicates that magmatic helium can be significantly variable, even between pre-crushed aliquots. Hence, magmatic helium, unlike cosmogenic 3 He, is highly variable, even in the case of aliquots of hundreds of grains. We suggest this is due to a strong nugget effect, possibly due to large fluid (or melt)-inclusions contained in phenocrysts.In addition, the fact that small and big grains have comparable radiogenic 4 He concentrations suggests that grain fragmentation during river transport is responsible for the lower magmatic helium content of the smallest grains. Therefore, one should preferably use small grain (0.2--0.5 mm) granulometry for in-situ cosmogenic 3 He analysis in mafic phenocrysts. Using the measured cosmogenic3 He, we calculate basin-averaged denudation rates of 70 textpm 20 and 57 textpm 5mmkyr − 1 , for the Mile and for the Tekeze river, respectively. These values are coherent with long-term denudation rates previously proposed from low-temperature thermochronology.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Puchol_etal2017_2,

title = {Limited impact of Quaternary glaciations on denudation rates in Central Asia},

author = {N. Puchol and J. Charreau and P. H. Blard and J. Lav\'{e} and S. Dominguez and R. Pik and D. Saint-Carlier and ASTER Team},

doi = {10.1130/B31475.1},

year  = {2017},

date = {2017-01-01},

journal = {GSA Bulletin},

volume = {129},

number = {3-4},

pages = {479--499},

abstract = {Because of its essential role in coupling climate and tectonics, denudationis a key parameter when constraining the history of Earthtextquoterightssurface. This is particularly true at the Pliocene-Pleistocene transition,and the potential impact of the onset of Quaternary glaciationsremains strongly debated. In the present study, we measured in situcosmogenic 10Be within continuous late Cenozoic sedimentary sectionsthat had already been dated using magnetostratigraphy. Thenew data were obtained from four sedimentary basins in the northernand southern Tianshan range (Central Asia). We first thoroughly discusshow in situ cosmogenic 10Be concentrations can be corrected forradioactive decay and for the contribution of postdepositional cosmogenicaccumulation to derive the paleo--denudation rates. Our analysisshows that, in the four sedimentary records, the potential bias remainslow enough to consider the derived denudation rates reliable.The four records, although likely influenced by local particularitiesdue to lithological heterogeneity and local tectonics, display similartrends of continuously increasing denudation between ca. 9 Ma andthe present. These rates have remained relatively high but steadysince 4 Ma, textasciitilde1.5 m.y. before the onset of the Quaternary glacial cycles.Though the rejuvenation of the Tianshan range since 11 Ma may explainmost of the progressive increase (texttimes5) in denudation, our datasuggest that the Quaternary glaciations had only a limited impact ondenudation in the Tianshan. Our data, however, indicate an increasein the spatial and high-frequency variability (\<1 m.y.) of the denudationrates between 3 and 1 Ma. This may correspond to a transientreadjustment of the landscape in response to the onset of Quaternaryglacial cycles},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Vacherat_etal2017,

title = {Rift-to-collision sediment routing in the Pyrenees : A synthesis from sedimentological, geochronological and kinematic constraints},

author = {A. Vacherat and F. Mouthereau and R. Pik and P. Huyghe and J. L. Paquette and F. Christophoul and N. Loget and B. Tibari},

year  = {2017},

date = {2017-01-01},

journal = {Earth-Science Reviews},

volume = {172},

pages = {43--74},

abstract = {Reconstructing long-term drainage evolution in collisional setting is key to deciphering between the drivers controlling landscape and time scales of syn-orogenic sediment transfer processes. Provenance studies in orogenic systems often exploit the geochronological record of past magmatic events in sediments to infer their source rocks. However, detrital age distribution may be difficult to be directly related to a specific source rock because it depends on whole rock composition and a robust stratigraphic and sedimentologic framework. Description of the provenance signal over the orogenic cycle from rift basin to its inversion as an orogenic prism may therefore appear to be a very challenging task. Here, we take advantage of an extensive set of geochronological dates in combination with sedimentological data in well-dated stratigraphic units to resolve uncertainties on grain provenance.We focus on the Pyrenees Mountains that developed in response to the inversion of European and Iberian continental margins from the Late Cretaceous to the Miocene. Inversion of hyper-extended rift basins in the Northern Pyrenees is recorded by specific cooling histories contrasting with the Southern Pyrenees where crustal extension was minor.We review and compile all available detrital thermochronological and geochronological data sets and provide new U/Pb and (U-Th-Sm)/He analyses on detrital zircon grains. This new data set allows us to re-examine the evolution of the sediments routing in the Pyrenees from rift-related Mesozoic basin evolution to tectonic inversion during Cenozoic foreland development. Together with sedimentological and petrographical constraints from syn-rift Mesozoic and syn-orogenic Cenozoic sediments, and within the frame of quantitative kinematic plate reconstructions based on existing rotation data, and balanced cross-sections, we examine the temporal and spatial evolution of sediment routing in the entire Pyrenean realm from rift to collision. Our paleogeographic reconstructions of the sediment dispersal pattern are presented for four key time steps at 100, 70, 55, and 40 Ma, accounting for Iberiatextquoterights plate motion.Early Cretaceous extension on the European margin led to the formation of multiple and narrow basins that were fed locally. This contrasts with the larger-scale pattern of sediment dispersal on the southern Iberia margin. The differences in sediments dispersal are shown to reflect first-order N-S asymmetry of extension. The asymmetry is maintained during the earliest stages of convergence in Late-Cretaceous -- Paleocene. The southern foreland basin exhibits large-scale longitudinal drainage patterns while sediments dispersal in the northern basin is controlled by inherited pre-orogenic E-W-striking basin architecture. In the Paleocene, the southwards migration of thrust sheets and underplating below the Axial Zone led to increasing exhumation at the origin of the emplacement of the first transverse drainage network in the Southern Pyrenees. Changes from dominant longitudinal to transverse drainage in the north occurred in the middle Eocene.Our study emphasizes the role played by the rifted margin on the syn-collisional sediment routing system. We anticipate that this main result could be transposed to other orogens that have resulted from rift basin inversion.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bot_etal2016,

title = {Miocene detachment faulting predating EPR propagation, Baja California Sur},

author = {A. Bot and C. Geoffroy and C. Authemayou and H. Bellon and D. Grandorge and R. Pik},

doi = {10.1002/2015TC004030},

year  = {2016},

date = {2016-01-01},

journal = {Tectonics},

volume = {35},

pages = {1153--1176},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Boutoux_etal2016,

title = {Thermal and structural evolution of the external Western Alps: insights from (U-Th-Sm)/He thermochronology and RSCM thermometry in the Aiguilles Rouges/Mont Blanc massifs},

author = {A. Boutoux and N. Bellahsen and U. Nanni and R. Pik and A. Verlaguet and Y. Rolland and O. Lacombe},

year  = {2016},

date = {2016-01-01},

journal = {Tectonophysics},

volume = {686},

pages = {109--123},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Medynski_etal2016,

title = {Magmatic cycles pace tectonic and morphological expression of rifting (Afar depression, Ethiopia)},

author = {S. Medynski and R. Pik and P. Burnard and S. Dumont and R. Grandin and A. Williams and P. H. Blard and I. Schimmelpfennig and C. Vye-Brown and L. France and D. Ayalew and L. Benedetti and G. Yirgu and ASTER team},

doi = {10.1016/j.epsl.2016.04.014},

year  = {2016},

date = {2016-01-01},

journal = {Earth and Planetary Science Letters},

volume = {446},

pages = {77--88},

abstract = {The existence of narrow axial volcanic zones of mid-oceanic ridges testifies of the underlying concentration of both melt distribution and tectonic strain. As a result of repeated diking and faulting, axial volcanic zones therefore represent a spectacular topographic expression of plate divergence. However, the submarine location of oceanic ridges makes it difficult to constrain the interplay between tectonic and magmatic processes in time and space. In this study, we use the Dabbahu--Manda Hararo (DMH) magmatic rift segment (Afar, Ethiopia) to provide quantitative constraints on the response of tectonic processes to variations in magma supply at divergent plate boundaries. The DMH magmatic rift segment is considered an analogue of an oceanic ridge, exhibiting a fault pattern, extension rate and topographic relief comparable to intermediate- to slow-spreading ridges. Here, we focus on the northern and central parts of DMH rift, where we present quantitative slip rates for the past 40 kyr for major and minor normal fault scarps in the vicinity of a recent (September 2005) dike intrusion. The data obtained show that the axial valley topography has been created by enhanced slip rates that occurred during periods of limited volcanism, suggestive of reduced magmatic activity, probably in association with changes in strain distribution in the crust. Our results indicate that the development of the axial valley topography has been regulated by the lifetimes of the magma reservoirs and their spatial distribution along the segment, and thus to the magmatic cycles of replenishment/differentiation (\<100 kyr). Our findings are also consistent with magma-induced deformation in magma-rich rift segments. The record of two tectonic events of metric vertical amplitude on the fault that accommodated the most part of surface displacement during the 2005 dike intrusion suggests that the latter type of intrusion occurs roughly every 10 kyr in the northern part of the DMH segment.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Stab_etal2016,

title = {Mode of rifting in magma-rich settings: Tectono-magmatic evolution of Central Afar},

author = {M. Stab and N. Bellahsen and R. Pik and X. Quidelleur and D. Ayalew and S. Leroy},

year  = {2016},

date = {2016-01-01},

journal = {Tectonics},

volume = {35},

pages = {2--38},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Tibari_etal2016,

title = {An Alternative Protocol for Single Zircon Dissolution with Application to (U-Th-Sm)/He Thermochronometry},

author = {B. Tibari and A. Vacherat and M. Stab and R. Pik and D. Yeghicheyan and P. Hild},

doi = {10.1111/j.1751-908X.2016.00375.x},

year  = {2016},

date = {2016-01-01},

journal = {Geostandards and Geoanalytical Research},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Vacherat_etal2016,

title = {Rift-to-collision transition recorded by tectono-thermal evolution of the northern Pyrenees},

author = {A. Vacherat and F. Mouthereau and R. Pik and N. Bellahsen and C. Gautheron and M. Bernet and M. Daudet and J. Balansa and B. Tibari and R. Pinna Jamme and J. Radal},

doi = {10.1002/2015TC004016},

year  = {2016},

date = {2016-01-01},

journal = {Tectonics},

volume = {35},

pages = {907--933},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Blard_etal2015,

title = {An inter-laboratory comparison of cosmogenic 3 He and radiogenic 4 He in the CRONUS-P pyroxene standard},

author = {P. H. Blard and G. Balco and P. G. Burnard and K. Farley and C. R. Fenton and R. Friedrich and A. J. T. Jull and S. Niedermann and R. Pik and J. M. Schaefer and E. M. Scott and D. L. Shuster and F. M. Stuart and M. Stute and B. Tibari and G. Winckler and L. Zimmermann},

doi = {http://dx.do10.1016/j.quageo.2014.08.004},

year  = {2015},

date = {2015-01-01},

journal = {Quaternary Geochronology},

volume = {26},

pages = {11--19},

abstract = {This study reports an inter-laboratory comparison of the 3 He and 4 He concentrations measured in the pyroxene material CRONUS-P. This forms part of the CRONUS-Earth and CRONUS-EU programs, which also produced a series of natural reference materials for in situ produced 26Al,10Be,14C,21Ne and 36Cl.Six laboratories (GFZ Potsdam, Caltech Pasadena, CRPG Nancy, SUERC Glasgow, BGC Berkeley, Lamont New York) participated in this intercomparison experiment, analyzing between 5 and 22 aliquots each. Intra-laboratory results yield 3He concentrations that are consistent with the reported analytical uncertainties, which suggests that 3He is homogeneous within CRONUS-P. The inter-laboratory dataset (66 determinations from the 6 different labs) is characterized by a global weighted mean of(5.02textpm0.12)x109at g-1 with an overdispersion of 5.6% (2s).4He is characterized by a larger variability than 3He, and by an inter-lab global weighted mean of (3.60textpm0.18)x1013 at g-1(2s) with an overdispersion of 10.4% (2s).There are, however, some systematic differences between the six laboratories. More precisely, 2 laboratories obtained mean 3He concentrations that are about 6%higher than the clustered other 4 laboratories. This systematic bias is larger than the analytical uncertainty and not related to the CRONUS-P material (see Schaefer et al., 2015). Reasons for these inter-laboratory offsets are difficult to identify but are discussed below. To improve the precision of cosmogenic 3He dating, we suggest that future studies presenting cosmogenic 3He results also report the3He concentration measured in the CRONUS-P material in the lab(s) used in a given study},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Liu_etal2015,

title = {Detection of trace-level uranium and samarium in glasses by combined laser-induced breakdown spectroscopy and plasma-induced fluorescence spectroscopy},

author = {L. Liu and S. Li and X. Huang and Y. Lu and K. Chen and R. Pik and L. Jiang and J. F. Silvain and Y. F. Lu},

year  = {2015},

date = {2015-01-01},

journal = {Journal of Analytical Atomic Spectrometry},

volume = {30},

pages = {1128--1132},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Medynski_etal2015,

title = {Stability of rift axis magma reservoirs: Spatial and temporal evolution of magma supply in the Dabbahu rift segment (Afar, Ethiopia) over the past 30 kyr},

author = {S. Medynski and R. Pik and P. Burnard and C. Vye-Brown and L. France and I. Schimmelpfennig and K. Whaler and N. Johnson and L. Benedetti and D. Ayelew and G. Yirgu},

doi = {10.1016/j.epsl.2014.11.002},

year  = {2015},

date = {2015-01-01},

journal = {Earth and Planetary Science Letters},

volume = {409},

pages = {278--289},

abstract = {Unravelling the volcanic history of the Dabbahu/Manda Hararo rift segment in the Afar depression (Ethiopia) using a combination of cosmogenic (36Cl and 3He) surface exposure dating of basaltic lava-flows, field observations, geological mapping and geochemistry, we show in this paper that magmatic activity in this rift segment alternates between two distinct magma chambers. Recent activity in the Dabbahu rift (notably the 2005--2010 dyking crises) has been fed by a seismically well-identified magma reservoir within the rift axis, and we show here that this magma body has been active over the last 30kyr. However, in addition to this axial magma reservoir, we highlight in this paper the importance of a second, distinct magma reservoir, located 15 km west of the current axis, which has been the principal focus of magma accumulation from 15 ka to the subrecent. Magma supply to the axial reservoir substantially decreased between 20 ka and the present day, while the flank reservoir appears to have been regularly supplied with magma since 15 ka ago, resulting in less variably differentiated lavas. The trace element characteristics of magmas from both reservoirs were generated by variable degrees of partial melting of a single homogeneous mantle source, but their respective magmas evolved separately in distinct crustal plumbing systems.Magmatism in the Dabbahu/Manda Hararo rift segment is not focussed within the current axial depression but instead is spread out over at least 15 kmon the western flank. This is consistent with magneto-telluric observations which show that two magma bodies are present below the segment, with the main accumulation of magma currently located below the western flank, precisely where the most voluminous recent (\<15 ka) flank volcanism is observed at the surface.Applying these observations to slow spreading mid-ocean ridges indicates that magma bodies likely have a lifetime of a least 20 ka, and that the continuity of magmatic activity is maintained by a system of separate relaying reservoirs, which could in return control the location of spreading. This long term (\>105yr) alternation between distinct crustal reservoirs located broadly at the same location relative to the segment appears to be a key feature for organizing and maintaining active spreading centres over stable soft points in the mantle.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Xiao_etal2015,

title = {The thermal history of the Baimaxueshan pluton in Deqin area and its implications for the tectonic-geomorphic evolution in the Three River Region of Tibetan Plateau},

author = {Y. Xiao and J. Liu and W. Wang and L. S. Zeng and K. J. Xie and R. Pik and Zhong N.},

year  = {2015},

date = {2015-01-01},

journal = {Acta Sinica Petrologica},

volume = {31},

pages = {1348--1360},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Mouthereau_etal2014,

title = {Placing limits to shortening evolution in the Pyrenees: role of margin architecture and implications for the Iberia/Europe convergence},

author = {F. Mouthereau and P. Y. Filleaudeau and A. Vacherat and R. Pik and O. Lacombe and M. G. Fellini and S. Castelltort and F. Christophoul and E. Masini},

year  = {2014},

date = {2014-01-01},

journal = {Tectonics},

volume = {33},

pages = {2283--2314},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Vacherat_etal2014,

title = {Thermal imprint of rift-related processes in orogens as recorded in the Pyrenees},

author = {A. Vacherat and F. Mouthereau and R. Pik and M. Bernet and C. Gautheron and E. Masini and L. Le Pourhiet and B. Tibari and A. Lahfid},

doi = {0.1016/j.epsl.2014.10.014},

year  = {2014},

date = {2014-01-01},

journal = {Earth and Planetary Science Letters},

volume = {408},

pages = {296--306},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bellahsen_etal2013,

title = {Pre-existing oblique transfer zones and transfer/transform relationships in continental margins: New insights from the southeastern Gulf of Aden, Socotra Island, Yemen},

author = {N. Bellahsen and S. Leroy and J. Autin and P. Razin and E. dtextquoterightAcremont and H. Sloan and R. Pik and A. Ahmed and K. Khanbari},

doi = {10.1016/j.tecto.2013.07.036},

year  = {2013},

date = {2013-01-01},

journal = {Tectonophysics},

volume = {607},

pages = {32--50},

abstract = {Transfer zones are ubiquitous features in continental rifts and margins, as are transform faults in oceanic lithosphere. Here, we present a structural study of the Hadibo Transfer Zone (HTZ), located in Socotra Island(Yemen) in the southeastern Gulf of Aden. There, we interpret this continental transfer fault zone to represent a reactivated pre-existing structure. Its trend is oblique to the direction of divergence and it has been active from the early up to the latest stages of rifting. One of the main oceanic fracture zones (FZ), the Hadibo--Sharbithat FZ, is aligned with and appears to be an extension of the HTZ and is probably genetically linked to it. Comparing this settingwith observations fromother Afro-Arabian rifts as well aswith passive marginsworldwide, it appears that many continental transfer zones are reactivated pre-existing structures, oblique to divergence. We therefore establish a classification system for oceanic FZ based upon their relationship with syn-rift structures. Type 1 FZ form at syn-rift structures and are late syn-rift to early syn-OCT. Type 2 FZ form during the OCT formation and Type 3 FZ form within the oceanic domain, after the oceanic spreading onset. The latter are controlled by far-field forces, magmatic processes, spreading rates, and oceanic crust rheology.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Medynski_etal2013,

title = {Controls on magmatic cycles and development of rift topography of the Manda Hararo segment (Afar, Ethiopia):Insights from cosmogenic 3He investigation of landscape evolution},

author = {S. Medynski and R. Pik and P. Burnard and A. Williams and C. Vye-Brown and D. Ferguson and P. H. Blard and L. France and G. Yirgu and J. I. Seid and D. Ayalew and A. Calvert},

doi = {doi.org/10.1016/j.epsl.2013.02.006},

year  = {2013},

date = {2013-01-01},

journal = {Earth and Planetary Science Letters},

volume = {367},

pages = {133--145},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Pik_etal2013,

title = {Structural control of basement denudation during rifting revealed by low-temperature (U--Th--Sm)/He thermochronology of the Socotra Island basement-Southern Gulf of Aden margin},

author = {R. Pik and N. Bellahsen and S. Leroy and Y. Den`ele and P. Razin and A. Ahmed},

doi = {10.1016/j.tecto.2013.07.038},

year  = {2013},

date = {2013-01-01},

journal = {Tectonophysics},

volume = {607},

pages = {17--31},

abstract = {In the Gulf of Aden, different types of fracture zones (F.Z.) have been defined and potential linkswith continental transfer zones have been proposed (Bellahsen et al., 2013-this volume-a). In this study, we investigate the denudation history of the south-eastern continental margin of the Gulf of Aden on the Socotra Island, in order to highlight the interplay of normal and transfer/transform tectonic structures in the course of rift evolution. Samples belong fromtwo distinct East andWest domains of the Socotra Island separated by the continental Hadibo Transfer Zone (HTZ). Tectonic denudation started during the Priabonian--Rupelian along low-angle normal faults and removed part of the overlying sedimentary formations allowing basement exhumation toward the surface (textasciitilde1.1--1.5 kmof exhumation). Forward t--Tmodelling of the data requires a slightly earlier date for initiation of rifting in the E-Socotra domain (textasciitilde38 textpm 2 Ma), compared to theW-Socotra domain (textasciitilde32 textpm 2 Ma), which suggests that the HTZ was already active at that time. A second major event of basement cooling and exhumation (additional textasciitilde 0.7--1 km), starting at about textasciitilde20 textpm 2 Ma, has only been recorded on the E-Socotra domain. This second denudation phase significantly post-dates local rifting period but appears synchronous with Ocean Continent Transition formation (OCT: 20--17.6 Ma). This late syn-OCT uplift is maximum close to the HTZ, in the wedge of footwall delimited by this transfer system and the steep north-dipping normal faults that accommodated the vertical motion. This particular pattern of uplift and denudation during the OCT reorganisation suggests that the late uplift of the margin can be strongly differential from a segment to another, depending on the amplitude of thinning experienced by each of the adjoining segments.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Denle_etal2012,

title = {The Cryogenian arc formation and successive high-K calc--alkaline plutons of Socotra Island (Yemen)},

author = {Y. Den`ele and S. Leroy and E. Pelleter and R. Pik and J. Y. Talbot and K. Khanbari},

doi = {10.1007/s12517-011-0476-3},

year  = {2012},

date = {2012-01-01},

journal = {Arabian Journal of Geosciences},

volume = {5},

pages = {903--924},

abstract = {The Socotra Island belongs to the southern rifted margin of the Gulf of Aden and occupied in Neoproterozoic times a key position to constrain the age and the nature of the largely hidden Neoproterozoic rocks of the Arabian plate. Ourintegrated field, petrographic, geochemical and geochronological study in the Neoproterozoic rocks recognises three main successive events: (a) high-temperature ductile deformation and metamorphism forming probably in a compressiveor transpressive regime; (b) mafic to intermediate intrusions as vertical sheets, kilometre-scale gabbro laccoliths, mafic dike swarm and lavas which present mainly a depleted arc signature with some evidences of evolution from an enriched-arc signature; (c) felsic intrusions mainly composed of highly potassic calc--alkaline and pinkish granites dated between 840 and 780 Ma. Relationships between the various petrographic types and U--Pb data suggest that these events occurred during a relatively short time span (80 Ma at max). Earlier high-temperature--low-pressure metamorphism stage as well as geochemical signature of mafic rocks show thatdevelopment of Cryogenian formations of Socotra were controlled successively by an Andean-arc and a back-arc setting. These features cannot be easily reconciled with those of the Arabian--Nubian shield to the west of Socotra and of the Mozambique Belt to the south. We propose that the Socotra basement was developed at an active margin close to the India block in Cryogenian times.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Puchol_etal2012,

title = {Les nucl\'{e}ides cosmog\'{e}niques : traceurs `a haute r\'{e}solution des taux dtextquoteright\'{e}rosion au cours du temps},

author = {N. Puchol and P. H. Blard and J. Charreau and R. Pik},

year  = {2012},

date = {2012-01-01},

journal = {G\'{e}ochronique},

number = {124},

pages = {19--21},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Zimmermann_etal2012,

title = {A New Single Vacuum Furnace Design for Cosmogenic 3He Dating},

author = {L. Zimmermann and P. H. Blard and P. Burnard and S. Medynski and R. Pik and N. Puchol},

doi = {10.1111/j.1751-908X.2011.00145.x},

year  = {2012},

date = {2012-01-01},

journal = {Geostandards and Geoanalytical Research},

pages = {1--9},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Perrineau_etal2011,

title = {Incision rate of the Yellow River in northeastern Tibet constrained by 10Be and 26Al cosmogenic isotopes dating of fluvial terraces: Implications for catchment evolution and plateau building},

author = {A. Perrineau and J. Van der Woerd and Y. Gaudemer and J. Liu-Zeng and R. Pik and R. Tapponnier and R. Thuizat and Z. Rongzhang},

year  = {2011},

date = {2011-01-01},

journal = {Geological Society of London Special Publication},

volume = {353},

pages = {189--219},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Pik2011,

title = {East African on the rise},

author = {R. Pik},

year  = {2011},

date = {2011-01-01},

journal = {Nature Geoscience},

volume = {4},

number = {10},

pages = {660--661},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Schimmelpfennig_etal2011,

title = {Calibration of cosmogenic 36Cl production rates by spallation of Ca and K on in lava flows samples from Mt. Etna ( 38textdegreeN, Italy) and Payun Matru (36textdegreeS, Argentina)},

author = {I. Schimmelpfennig and L. Benedetti and V. Garreta and R. Pik and P. H. Blard and P. G. Burnard and D. Bourl`es and R. Finkel and K. Ammond and C. Dunaigre},

year  = {2011},

date = {2011-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {75},

number = {10},

pages = {2611--2632},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Schimmelpfennig_etal2011_2,

title = {Inter-comparison of cosmogenic in-situ 3He, 21Ne and 36Cl at low latitude along an altitude transect on the SE slope of Kilimanjaro volcano (3textdegreeS, Tanzania)},

author = {I. Schimmelpfennig and A. Williams and R. Pik and P. Burnard and S. Niedermann and R. Finkel and B. Schneider and L. Benedetti},

year  = {2011},

date = {2011-01-01},

journal = {Quaternary Geochronology},

volume = {6},

number = {5},

pages = {425--436},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Roudil_etal2010,

title = {Thermal desorption gas chromatography and positron annihilation spectroscopy contribution to alpha decay studies in actinide-doped matrices},

author = {D. Roudil and C. Jegou and R. Pik and M. F. Barthe and M. Cuney and F. Vella and Y. Pipon and B. Foch and V. Broudic},

year  = {2010},

date = {2010-01-01},

journal = {IEEE Trans. Nucl. Sci.},

volume = {57},

pages = {3676--3677},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Godard_etal2009_2,

title = {Late Cenozoic evolution of the central Longmen Shan, eastern Tibet: Insight from (U-Th)/He thermochronometry},

author = {V. Godard and R. Pik and J. Lav\'{e} and R. Cattin and B. Tibari and J. Sigoyer and M. Pubellier and J. Zhu},

doi = {10.1029/2008TC002407},

year  = {2009},

date = {2009-01-01},

journal = {Tectonics},

volume = {28},

number = {TC5009},

pages = {1--17},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Pik+Marty2009,

title = {Helium isotopic signature of modern and fossil fluids associated with the Corinth rift fault zone (Greece): Implication for fault connectivity in the lower crust},

author = {R. Pik and B. Marty},

doi = {10.1016/j.chemgeo.2008.09.024},

year  = {2009},

date = {2009-01-01},

journal = {Chemical Geology},

volume = {266},

number = {1-2},

pages = {67--75},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Schimmelpfennig_etal2009,

title = {Sources of in-situ Cl-36 in basaltic rocks. Implications for calibration of production rates},

author = {I. Schimmelpfennig and L. Benedetti and R. Finkel and R. Pik and P. H. Blard and D. Bourles and P. Burnard and A. Williams},

doi = {10.1016/j.quageo.2009.06.003},

issn = {1871-1014},

year  = {2009},

date = {2009-01-01},

journal = {Quaternary Geochronology},

volume = {4},

number = {6},

pages = {441--461},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Blard+Pik2008,

title = {An alternative isochron method for measuring cosmogenic He-3 in lava flows},

author = {P. H. Blard and R. Pik},

doi = {10.1016/j.chemgeo.2008.02.004},

year  = {2008},

date = {2008-01-01},

journal = {Chemical Geology},

volume = {251},

number = {1-4},

pages = {20--32},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Maurel_etal2008,

title = {The Meso-Cenozoic thermo-tectonic evolution of the Eastern Pyrenees: an 40Ar/39Ar fission track and (U/Th)/He thermochronological study of the Canigou and Mont-Louis massifs},

author = {O. Maurel and P. Moni\'{e} and R. Pik and N. Arnaud and M. Brunel and M. Jolivet},

doi = {10.1007/s00531-007-0179-x},

year  = {2008},

date = {2008-01-01},

journal = {International Journal of Earth Sciences},

volume = {97},

number = {3},

pages = {565--584},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Pik_etal2008,

title = {Timing of East African Rift development in southern Ethiopia: Implication for mantle plume activity and evolution of topography},

author = {R. Pik and B. Marty and J. Carignan and G. Yirgu and T. Ayalew},

doi = {10.1130/G24233A.1},

year  = {2008},

date = {2008-01-01},

journal = {Geology},

volume = {36},

number = {2},

pages = {167--170},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Roudil_etal2008,

title = {Diffusion of radiogenic helium in natural uranium oxides},

author = {D. Roudil and J. Bonhoure and R. Pik},

doi = {10.1016/j.jnucmat.2008.05.001},

year  = {2008},

date = {2008-01-01},

journal = {Journal of Nuclear Materials},

volume = {378},

number = {1},

pages = {70--78},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Blard_etal2007,

title = {Persistence of full glacial conditions in the central Pacific until 15,000 years ago},

author = {P. H. Blard and J. Lav\'{e} and R. Pik and P. Wagnon and D. Bourl`es},

doi = {10.1038/nature06142},

year  = {2007},

date = {2007-01-01},

journal = {Nature},

volume = {449},

number = {7162},

pages = {585--591},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bourgeois_etal2007,

title = {Separation of rifting and lithospheric folding signatures in the NW-Alpine foreland},

author = {O. Bourgeois and M. Ford and M. Diraison and C. Le Carlier de Veslud and M. Gerbault and R. Pik and N. Ruby and S. Bonnet},

doi = {10.1007/s00531-007-0202-2},

year  = {2007},

date = {2007-01-01},

journal = {International Journal of Earth Sciences},

volume = {96},

pages = {1003--1031},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dunai_etal2007,

title = {Production of 3He in crustal rocks by cosmogenic thermal neutrons},

author = {T. J. Dunai and F. M. Stuart and R. Pik and P. Burnard and E. Gayer},

doi = {10.1016/j.epsl.2007.03.031},

year  = {2007},

date = {2007-01-01},

journal = {Earth and Planetary Science Letters},

volume = {258},

number = {1-2},

pages = {228--236},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Montagner_etal2007,

title = {Mantle upwellings and convective instabilities revealed by seismic tomography and helium isotope geochemistry beneath eastern Africa},

author = {J. P. Montagner and B. Marty and E. Stutzmann and D. Sicilia and M. Cara and R. Pik and J. J. L\'{e}v^eque and G. Roult and E. Beucler and E. Debayle},

doi = {10.1029/2007GL031098},

year  = {2007},

date = {2007-01-01},

journal = {Geophysical Research Letters},

volume = {34},

pages = {L21303},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bernet_etal2006,

title = {Miocene to recent exhumation of the central Himalaya determined from combined detrital zircon fission-track and U/Pb analysis of Siwalik sediments, western Nepal},

author = {M. Bernet and P. Van der Beek and R. Pik and P. Huyghe and J. L. Mugnier and E. Labrin and A. Szulc},

doi = {10.1111/j.1365-2117.2006.00303.x},

year  = {2006},

date = {2006-01-01},

journal = {Basin Research},

volume = {18},

number = {4},

pages = {393--412},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kraml_etal2006,

title = {A new multi-mineral age reference material for 40Ar/39Ar, (U-Th)/He and fission track dating methods: the Limberg t3 tuff},

author = {M. Kraml and R. Pik and M. Rahn and R. Selbekk and J. Carignan and J. Keller},

doi = {10.1111/j.1751-908X.2006.tb00914.x},

year  = {2006},

date = {2006-01-01},

journal = {Geostandards and Geoanalytical Research},

volume = {30},

number = {2},

pages = {73--86},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Pik_etal2006,

title = {How many mantle plumes in Africa?: The geochemical point of view},

author = {R. Pik and B. Marty and D. R. Hilton},

doi = {10.1016/j.chemgeo.2005.09.016},

year  = {2006},

date = {2006-01-01},

journal = {Chemical Geology},

volume = {226},

pages = {100--114},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Boyet_etal2005,

title = {A search for Nd-142 evidence of primordial mantle heterogeneities in plume basalts},

author = {M. Boyet and M. O. Garcia and R. Pik and F. Albar`ede},

doi = {10.1029/2004GL021873},

year  = {2005},

date = {2005-01-01},

journal = {Geophysical Research Letters},

volume = {32},

number = {4},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Yokochi_etal2005,

title = {High 3He/4He ratios in peridotite xenoliths from SW Japan revisited: evidence for cosmogenic 3He released by vacuum crushing},

author = {R. Yokochi and B. Marty and R. Pik and P. Burnard},

doi = {10.1029/2004GC000836},

year  = {2005},

date = {2005-01-01},

journal = {Geochemistry Geophysics Geosystems G3},

volume = {6},

number = {1},

pages = {1--12},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ayalew_etal2002,

title = {Source, genesis and timing of giant ignimbrite deposits associated with Ethiopian continental flood basalts},

author = {D. Ayalew and P. Barbey and B. Marty and L. Reisberg and G. Yirgu and R. Pik},

doi = {10.1016/S0016-7037(01)00834-1},

year  = {2002},

date = {2002-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {66},

number = {8},

pages = {1429--1448},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ayalew_etal2002_2,

title = {Origin and timing of Ethiopian Ignimbrites},

author = {D. Ayalew and P. Barbey and B. Marty and L. Reisberg and G. Yirgu and R. Pik},

year  = {2002},

date = {2002-01-01},

journal = {Geological Journal},

volume = {36},

pages = {409--419},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Rvillon_etal2002,

title = {Heterogeneity of the Caribbean plateau mantle source: Sr, O and He isotopic compositions of olivine and clinopyroxene from Gorgona Island},

author = {S. R\'{e}villon and C. Chauvel and N. T. Arndt and R. Pik and F. Martineau and S. Fourcade and B. Marty},

doi = {10.1016/S0012-821X(02)01003-8},

year  = {2002},

date = {2002-01-01},

journal = {Earth and Planetary Science Letters},

volume = {205},

number = {1-2},

pages = {91--106},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Quattrocchi_etal2000,

title = {Geochemical changes at the Bagni di Triponzo thermal spring during the Umbria Marche 1997-1998 seismic sequence},

author = {F. Quattrocchi and R. Pik and M. Angelone and M. Barbieri and A. Conti and S. Guerra and S. Lombardi and B. Marty},

doi = {10.1023/A:1026590028678},

year  = {2000},

date = {2000-01-01},

urldate = {2000-01-01},

journal = {Journal of Seismology},

volume = {4},

number = {4},

pages = {567--587},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dereje_etal1999,

title = {Geochemical and isotopic (Sr, Nd and Pb) characteristics of volcanic rocks from southwestern Ethiopia},

author = {A. Dereje and G. Yirgu and R. Pik},

doi = {10.1016/S0899-5362(99)00104-9},

year  = {1999},

date = {1999-01-01},

journal = {Journal of African Earth Sciences},

volume = {29},

number = {2},

pages = {381--391},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Pik_etal1999,

title = {Isotopic and trace element signatures of Ethiopian flood basalts : evidence for plume-lithosph`ere interactions},

author = {R. Pik and C. Deniel and C. Coulon and G. Yirgu and B. Marty},

doi = {10.1016/S0016-7037(99)00141-6},

year  = {1999},

date = {1999-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {63},

number = {15},

pages = {2263--2279},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Roger_etal1999,

title = {An insight on the nature, composition and evolution of the lithospheric mantle beneath the north-western Ethiopian plateau : the ultrabasic xenoliths from the Tana Lake Province},

author = {S. Roger and J. M. Dautria and C. Coulon and R. Pik and G. Yirgu and A. Michard and P. Legros and A. Dereje},

year  = {1999},

date = {1999-01-01},

journal = {Acta Vulcanologica},

volume = {11},

number = {1},

pages = {161--168},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Pik_etal1998,

title = {The Northwestern Ethiopian Plateau flood basalts : Classification and spatial distributionof magma types},

author = {R. Pik and C. Deniel and C. Coulon and G. Yirgu and C. Hofmann and A. Dereje},

year  = {1998},

date = {1998-01-01},

journal = {Journal of Volcanology and Geothermal Research},

volume = {81},

pages = {91--111},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Rochette_etal1998,

title = {Magnetostratigraphy and timing of the Oligocene Ethiopian traps},

author = {P. Rochette and E. Tamrat and G. F\'{e}raud and R. Pik and V. Courtillot and E. Ketefo and C. Coulon and C. Hoffmann and D. Vandamme and G. Yirgu},

doi = {10.1016/S0012-821X(98)00241-6},

year  = {1998},

date = {1998-01-01},

journal = {Earth and Planetary Science Letters},

volume = {164},

pages = {497--510},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Hofmann_etal1997,

title = {Timing of the Ethiopian flood basalt event and implications for plume birth and global change},

author = {C. Hofmann and V. Courtillot and G. F\'{e}raud and P. Rochette and G. Yirgu and E. Ketefo and R. Pik},

doi = {10.1038/39853},

year  = {1997},

date = {1997-01-01},

journal = {Nature},

volume = {389},

pages = {838--841},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Roger_etal1997,

title = {Rifting actif ou passif en Ethiopie ?: El\'{e}ments de r\'{e}ponse apport\'{e}s par ltextquoteright\'{e}tude des x\'{e}nolites p\'{e}ridotites de la r\'{e}gion du lac Tana},

author = {S. Roger and R. Pik and J. M. Dautria and C. Coulon and G. Yirgu and A. Dereje and P. Legros},

year  = {1997},

date = {1997-01-01},

journal = {Comptes Rendus de ltextquoterightAcad\'{e}mie des Sciences, s\'{e}rie II},

volume = {324},

pages = {1009--1016},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Marty_etal1996,

title = {Helium isotopic variations in Ethiopian Plume Lavas: nature of magmatic sources and limit on lower mantle contribution},

author = {B. Marty and R. Pik and G. Yirgu},

year  = {1996},

date = {1996-01-01},

journal = {Earth and Planetary Science Letters},

volume = {144},

pages = {223--237},

keywords = {},

pubstate = {published},

tppubtype = {article}

}