GSA Bulletin最新文献

{"title":"Modern dextral strain controls active hydrothermal systems in the southeastern Canadian Cordillera","authors":"Theron D. Finley, S. Johnston, M. Unsworth, Jonathan C. Banks, D. Pană","doi":"10.1130/b36500.1","DOIUrl":"https://doi.org/10.1130/b36500.1","url":null,"abstract":"Thermal springs in the southeastern Canadian Cordillera occur in association with several major fault zones, which may permit deep circulation of fluid through fractured reservoirs to depths greater than 2 km. Both the current stress field and the most recent kinematics of these faults likely play a significant role in localizing hydrothermal upwellings but are poorly resolved. In this paper, we present new data from structural mapping along the Columbia River, Slocan Lake, Purcell Trench, Southern Rocky Mountain Trench, and Redwall faults. Fault plane and slickenfiber orientations measured in the field indicate a previously unidentified, post-Eocene phase of dextral strike-slip kinematics on these faults, which have historically been mapped primarily as Eocene extensional structures. The NE−SW maximum principal stress required for these kinematics shares a similar orientation to the present-day stress field derived from crustal earthquake focal mechanisms, which suggests dextral slip may be a recent and ongoing development that continues at the present time. On a regional scale, there is a positive correlation between the locations of springs and regions with elevated seismicity. At the local scale, geothermal upwellings may be controlled by local zones of enhanced permeability including fault intersections and strain-transfer zones. The identification of favorable structural settings may enable discovery of hidden (a.k.a. blind) geothermal energy resources.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123876112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The grainsize of volcanic fall deposits: Spatial trends and physical controls","authors":"J. Eychenne, S. Engwell","doi":"10.1130/b36275.1","DOIUrl":"https://doi.org/10.1130/b36275.1","url":null,"abstract":"Volcanic tephra fall deposits, which form during explosive eruptions, are commonly characterized in terms of their thickness and grainsize. While significant efforts have been undertaken to relate spatial trends in thickness to plume dispersion processes, comparably few studies have focused on understanding variations in grainsize. Yet, grainsize is a key parameter providing insight into eruption dynamics, from magma fragmentation to plume transport processes, and modulates the impacts of tephra. Here, we present a set of grainsize data extracted from the published record for 56 deposits that represent a range of eruption intensities and magnitudes. We systematically analyze the deposits in terms of modality (bimodal or unimodal grainsize distributions) and provide the median particle diameter with distance from source for component distribution modes. We found that bimodal fall deposits are formed by eruptions with large amounts of fine particles (<100 µm) and that all tephra-fall deposits show characteristic patterns of grainsize decay with distance from source that can be related to eruption plume height and thus intensity. The grainsize decay trends are also related to ash dispersion and deposition processes such as individual particle settling versus collective settling mechanisms. The maximum distance from source reached by particles of different sizes is controlled by a combination of source and transport processes. This data set provides insight into the preservation potential of deposits of different grainsizes at varying distances from their sources. Finally, we emphasize the importance of using grainsize trends in combination with thickness trends to interpret tephra-fall deposit records.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122949685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Origin of the Songpan-Garze Terrane on the northeastern Tibetan Plateau, eastern segment of the Tethyan tectonic domain: A Middle Permian−Early Triassic intracontinental rifting system","authors":"Songnan Liu, Yu Wang","doi":"10.1130/b36468.1","DOIUrl":"https://doi.org/10.1130/b36468.1","url":null,"abstract":"The initiation of a continental rift or the birth of an oceanic basin, and their long-term evolution, are challenges in the understanding of the evolution of regional and global tectonics. Rifts develop within the interior or margins of plates, essentially as extensional structures, and they have been studied widely since the discovery of plate tectonics. The eastern segment of the Paleo-Tethys traversed central Asia, its structural features, timing, geological setting, and geodynamic mechanisms are poorly understood. The Songpan-Garze Terrane (SGT) on the northeastern Tibetan Plateau has been regarded as either a remnant of the Paleo-Tethys Ocean or a continental rift basin. Different interpretations of the SGT lead to various tectonic reconstructions between Gondwana and Laurasia. Here, sedimentology, geochemistry, and geochronology have been applied to the southern and northern parts of the SGT to reconstruct the initiation of a Permian rift system. In this area, for the first time, field investigation reveals that the SGT is characterized by a continuous succession of Permian−Lower Triassic terrestrial-neritic deposits and ocean island basalt (OIB)-type basalts, and that it developed as an intracontinental rift basin in the Yangtze Block. Zircons from gabbros with OIB-type geochemical signatures intruded in the southern SGT yield U-Pb ages of 263−254 Ma, constraining the timing of the initial rifting. Proterozoic felsic rocks collected from the southern SGT yield U-Pb ages of 761−865 Ma, and they are petrologically and geochemically comparable to Neoproterozoic basement rocks along the western margin of the Yangtze Block. The Middle−Late Permian volcano-sedimentary sequences of the SGT and their geochemistry and geochronology are comparable to rift sequences in the Panxi region of the western Yangtze Block. Thus, it has been proposed that the SGT originated as an intracontinental rift within the Yangtze Block during the Middle Permian−Early Triassic, and that it continued to deepen as a rift basin through the Middle−Late Triassic.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132121509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Late Mesozoic elevation history of the north Taihang Mountains, China: Constraints from clumped isotope geochemistry","authors":"Yixiong Wen, Laiming Zhang, Yalin Li, K. Huntington, Tianjie Jin, A. Schauer, Chengshan Wang","doi":"10.1130/b36364.1","DOIUrl":"https://doi.org/10.1130/b36364.1","url":null,"abstract":"A series of tectonic events during the late Mesozoic, including the Yanshanian Orogeny and the Early Cretaceous tectonic extension, reshaped the tectonic regime and landscape of North China (NC). During this period, the Taihang Mountains (THM) became a prominent geomorphic and ecological separation zone, which separates NC into regions with different landforms, tectonic settings, and climatic regimes. The uplift history of the THM during the late Mesozoic is of great interest, since it is critical to constrain the geodynamic and regional climatic evolution of NC. In this study, we report the first carbonate clumped isotope thermometry (Δ47) data for paleosol carbonates from this region to constrain the paleoelevation of the north THM during the late Mesozoic. Our result indicates that the north THM was almost certainly 2.0 ± 0.8 km elevation at ca. 160 Ma associated with crust thickening and shortening. After the collapse of the eastern North China Craton (NCC), the north THM maintained high elevation at ca. 113 Ma (2.7 ± 0.7 km). The findings suggest that the present topographic features of NC may have been established in the Early Cretaceous. Finally, our study suggests elevation decrease at the end of the Early Cretaceous (ca. 110−100 Ma), which is possibly related to isostatic adjustment caused by asthenosphere upwelling and partial crustal thinning in the central NCC.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"107 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133644839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cenozoic kinematic histories of the Tidding and Lohit thrusts in the northern Indo-Burma Ranges: Implications for crustal thickening and exhumation of Gangdese lower arc crust along the Indus-Yarlung suture zone","authors":"P. Haproff, D. Levy, A. Zuza, Julian D. Hooker, M. Heizler, D. Stockli, M. Braza","doi":"10.1130/b36323.1","DOIUrl":"https://doi.org/10.1130/b36323.1","url":null,"abstract":"Crustal thickening has been a key process of collision-induced Cenozoic deformation along the Indus-Yarlung suture zone, yet the timing, geometric relationships, and along-strike continuities of major thrusts, such as the Great Counter thrust and Gangdese thrust, remain inadequately understood. In this study, we present findings of geologic mapping and thermo- and geochronologic, geochemical, microstructural, and geothermobarometric analyses from the easternmost Indus-Yarlung suture zone exposed in the northern Indo-Burma Ranges. Specifically, we investigate the Lohit and Tidding thrust shear zones and their respective hanging wall rocks of the Lohit Plutonic Complex and Tidding and Mayodia mélange complexes. Field observations are consistent with ductile deformation concentrated along the top-to-the-south Tidding thrust shear zone, which is in contrast to the top-to-the-north Great Counter thrust at the same structural position to the west. Upper amphibolite-facies metamorphism of mélange rocks at ∼9−10 kbar (∼34−39 km) occurred prior to ca. 36−30 Ma exhumation during slip along the Tidding thrust shear zone. To the north, the ∼5-km-wide Lohit thrust shear zone has a subvertical geometry and north-side-up kinematics. Cretaceous arc granitoids of the Lohit Plutonic Complex were emplaced at ∼32−40 km depth in crust estimated to be ∼38−52 km thick at that time. These rocks cooled from ca. 25 Ma to 10 Ma due to slip along the Lohit thrust shear zone. We demonstrate that the Lohit thrust shear zone, Gangdese thrust, and Yarlung-Tsangpo Canyon thrust have comparable hanging wall and footwall rocks, structural geometries, kinematics, and timing. Based on these similarities, we interpret that these thrusts formed segments of a laterally continuous thrust system, which served as the preeminent crustal thickening structure along the Neotethys-southern Lhasa terrane margin and exhumed Gangdese lower arc crust in Oligocene−Miocene time.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125568703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aspect-dependent bedrock weathering, cliff retreat, and cliff morphology in a hyperarid environment","authors":"Yuval Shmilovitz, Y. Enzel, E. Morin, M. Armon, A. Matmon, A. Mushkin, J. Pederson, I. Haviv","doi":"10.1130/b36442.1","DOIUrl":"https://doi.org/10.1130/b36442.1","url":null,"abstract":"Deciphering aspect-related hillslope asymmetry can enhance our understanding of the influence of climate on Earth’s surface morphology and the linkage between topographic morphology and erosion processes. Although hillslope asymmetry is documented worldwide, the role of microclimatic factors in the evolution of dryland cliffs has received little attention. Here, we address this gap by quantifying aspect-dependent bedrock weathering, slope-rill morphology, and sub-cliff clast transport rates in the hyperarid Negev desert, Israel, based on light detection and ranging (LiDAR)-derived topography, clast-size measurements, and cosmogenic 10Be concentrations. Cliff retreat rates were evaluated using extrapolated profiles from dated talus flatirons and 10Be measurements from the cliff face and sub-cliff sediments. We document systematic, aspect-dependent patterns of south-facing slopes being less steep and finer-grained relative to east- and north-facing aspects. In addition, cliff retreat and clast transport rates on slopes of the south-facing aspect are faster compared to the other aspects. Our data demonstrate that bedrock weathering of the cliff face and the corresponding grain size of cliff-derived clasts delivered to the slopes constitute a first-order control on cliff retreat and sediment transport rates. We demonstrate that the morphology of the cliff and the pattern of bedrock weathering co-vary with the solar radiation flux and hence that cliff evolution in hyperarid regions is modulated by aspect-dependent solar radiation. These results help to better understand interactions between climate and dryland surface processes.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"223 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131521607","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Late Cretaceous−early Paleogene rise of the Gangdese magmatic arc (south Tibet) from sea level to high mountains","authors":"Qiang Xu, L. Ding, Yu Cao, F. Cai, Shun Li, X. Tan, S. Kershaw, Hao Tang","doi":"10.1130/b36438.1","DOIUrl":"https://doi.org/10.1130/b36438.1","url":null,"abstract":"Recognition of the existence of an Andean-type continental margin in southern Tibet prior to its collision with India has provided crucial constraints on the formation of the Tibetan Plateau and South Asian climate evolution. Here, we focused on well-dated Late Cretaceous successions in the Linzhou Basin and determined the elevation changes from sea level to high mountains in the Gangdese magmatic arc in southern Tibet. Our results show that the Linzhou Basin was still submerged in the Tethyan Sea at around 92 Ma when it accumulated Cenomanian (ca. 105−92 Ma) shallow-marine orbitolinid-bearing limestones (Takena Formation); these limestones are unconformably overlain by Campanian (83−78 Ma) fluvial-lacustrine deposits (Shexing Formation) after an ∼9 m.y. depositional hiatus. A prominent unconformity between the tightly folded Shexing Formation and gently tilted overlying Paleocene−Eocene Linzizong successions represents the formation of the regional Lhasaplano ca. 70 Ma, which may have been linked to the rise of an Andean-type Gangdese mountain range along the southern margin of the Lhasa terrane. Using carbonate oxygen isotope and clumped isotope thermometry data from the Shexing Formation paleosols, we quantitatively documented the rise of the Andean-type Gangdese Mountains with a peneplain surface at an elevation of 2.7 +0.5/−0.9 km above sea level prior to onset of the India-Asia collision ca. 65−63 Ma. This scenario of surface gain may have been an isostatic compensation response to the crust thickening to over 50 km during the Late Cretaceous. Subsequently, the surface isostatically rose to its near-present elevation of ∼4.6 km due to the removal of overthickened mantle lithosphere and revival of intense Gangdese magmatism by 56 Ma.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"184 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124316320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Growth of early Paleozoic continental crust linked to the Proto-Tethys subduction and continental collision in the East Kunlun Orogen, northern Tibetan Plateau","authors":"L. Fu, L. Bagas, Jun-hao Wei, Yao Chen, Jia-jie Chen, Xu Zhao, Zhixin Zhao, Aobing Li, Weikang Zhang","doi":"10.1130/b36292.1","DOIUrl":"https://doi.org/10.1130/b36292.1","url":null,"abstract":"The East Kunlun Orogen (EKO) in the northern Tibetan Plateau records two continental collisional orogenic events and magmatism in early Paleozoic and early Mesozoic. However, possible magmatic additions to the continental crust growth of the EKO in different tectonic stages of early Paleozoic collisional orogeny have been overlooked. Three phases of early Paleozoic plutons from the Xiangride-Kuhai area in the east of the EKO have been chosen for detailed investigation and the results are reported here. The oldest magmatic suite (Stage 1) includes the ca. 471 Ma Qurelong Monzodiorite and ca. 454 Ma granodiorite in the Zhiyu Intrusive Complex. The monzodiorite has a sanukitoid-like composition with high TiO2 and Y contents and is interpreted as being derived from partial melting of metasomatized mantle wedge lherzolite. The granodiorite is typified by its high SiO2 content, high Sr/Y ratio, and depleted Hf isotope, and is interpreted as an adakite-like melt derived from the melting of a subducted Proto-Tethys oceanic crust. The magmatism can be linked to northward subduction of the Proto-Tethys Ocean between 520 and 450 Ma. Stage 2 magmatism is represented by a plutonic suite emplaced during ca. 450−431 Ma with an I-type granitic composition. Of these, the ca. 447 Ma Kengdenongshe Intrusion composed of peraluminous granite with enriched Nd-Hf isotopes is indicative of a Mesoproterozoic igneous source in the orogen. The ca. 450−434 Ma monzogranite and granodiorite in the Walega and Zhiyu intrusive complexes exhibit variable element and isotope compositions. They would have been generated by magma mixing of felsic melts from the old crust and mafic magmas derived from the metasomatized lithospheric mantle, with a mafic melt proportion of >30%. The ca. 431 Ma quartz diorite in the Walega Intrusive Complex is formed through crustal assimilation and fractional crystallization of mafic magmas derived from the metasomatized lithospheric mantle, with a mafic melt proportion >60%. Stage 2 suite was emplaced during the closure of Proto-Tethys oceanic branches and subsequent continental collision during 450−426 Ma. Magmatism diminished between ca. 426 and 410 Ma during exhumation of the continental lithosphere as indicated by the presence of retrograde eclogites in the EKO. Stage 3 magmatic suite includes the ca. 408 Ma Langmuri Intrusion and ca. 403 Ma Niantang Syenogranite. These plutons are adakite-like or have an A-type granitic composition and are enriched in Nd-Hf isotopes. They might have been derived from the remelting of old and juvenile continental crust in a post-collisional extensional setting during 410−390 Ma. Identification of partial melts, derived from the subducted Proto-Tethys oceanic crust and metasomatized lithospheric mantle in stage 1 and 2 plutons, show that the subcrustal materials have been significantly transferred to the overlying continental crust. Hence the magmatism in oceanic subduction (Stage 1) and continental collision (Stag","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"85 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128687539","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Termination of the Paleo-Asian Ocean in the Beishan orogen, NW China: Constraints from detrital zircon U-Pb age and Hf isotope analysis of turbidites","authors":"Q. Guo, Sun‐Lin Chung, Hao-Yang Lee, W. Xiao, Quanlin Hou","doi":"10.1130/b36455.1","DOIUrl":"https://doi.org/10.1130/b36455.1","url":null,"abstract":"The termination of the Paleo-Asian Ocean, including duration and architecture, is controversial and has led to different reconstructions of the Central Asian orogenic belt. Deep-marine turbidites are of great significance in constraining the evolution of the oceanic basin. The youngest marine turbidites in the Beishan orogen in the central part of the southern Central Asian orogenic belt are separated by the Liuyuan mélange into two sections, the South turbidites and North turbidites. Detrital zircon grains from South turbidites yielded a maximum depositional age of 255 Ma. Those from North turbidites yielded a maximum depositional age of 254 Ma. Most of the Precambrian zircons of South turbidites have concentrated εHf(t) values (−6 to −2.6), whereas those of North turbidites range from −12.6 to +10.4, indicating different provenances. The North turbidites also have more positive whole-rock εNd(t) values (−0.5 to +1.1) than the South turbidites (−4.2 to −2.4), suggesting more juvenile or less evolved crustal components in the source. Detailed comparison of the detrital zircon ages and Hf-Nd isotopic characteristics with igneous and metamorphic rocks in the south Beishan area distinguishes two sources. These findings constrain the Liuyuan suture as the latest suture in the Beishan region, occurring no earlier than 254 Ma. The youngest peak age of detrital zircons of the youngest marine sedimentary rocks in the southern Central Asian orogenic belt becomes younger eastward from 288 Ma to 247 Ma, characterizing the closure duration of the Paleo-Asian Ocean from west to east in ∼40 m.y. This study finds that the youngest turbidites in the Beishan orogen not only record sedimentary processes in response to the final episode of orogenic evolution in the southern Central Asian orogenic belt, but they also constrain how and when an archipelago-type accretionary orogen terminated.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128154949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tracing decarbonated eclogite in the mantle sources of Tarim continental flood basalts using Zn isotopes","authors":"Zhenchao Wang, Zhaochong Zhang, M. Reichow, W. Tian, Weiliang Kong, Bingxiang Liu","doi":"10.1130/b36502.1","DOIUrl":"https://doi.org/10.1130/b36502.1","url":null,"abstract":"Recycled oceanic crust is believed to have played an important role in the formation of continental flood basalts, whereas the involvement of large amounts of CO2 derived from recycled marine carbonate in their mantle sources is highly debated. Zn isotopes have great potential to trace recycled carbonate due to the distinctly different δ66Zn values between marine carbonates and the mantle. Representative continental flood basalt samples from Keping (Group1) and Yingmai and Shengli (Group 2) in Tarim, NW China, were collected to investigate their mantle sources, and their Zn isotopes were studied systematically for the first time. The Zn isotope values of Keping basalts (between 0.29‰ ± 0.03‰ and 0.32‰ ± 0.05‰) are higher than values in the primitive mantle (δ66Zn = 0.16‰ ± 0.06‰) but similar to those of mid-ocean-ridge basalt (MORB; δ66Zn = 0.24‰−0.31‰). Considering their high fractionation (e.g., Mg# = 0.28−0.37) and potential involvement of crustal contamination (87Sr/86Sri between 0.70720 and 0.70779; εNd between −3.2 and −1.9), their Zn isotopes may not conclusively point to a carbonated mantle source. In contrast, Yingmai and Shengli basalts show heavy Zn isotope values (between 0.32‰ ± 0.03‰ and 0.39‰ ± 0.03‰), nonradiogenic 87Sr/86Sri (0.70459‒0.70518) and εNd(t) (between −1.3 and 0.1) signatures, and less fractionation (Mg# = 0.46−0.71), implying the involvement of recycled carbonate components in their mantle source. Nonetheless, the lack of negative Zr, Hf, and Ti anomalies, low CaO/Al2O3 ratios, and high SiO2 contents preclude direct melting of carbonate-bearing mantle. Alternatively, these features may suggest the melting of decarbonated subducted eclogite and variable interaction with subsolidus peridotite. This assumption is consistent with the positive correlations of δ66Zn with Gd/Yb and Sm/Yb ratios and Zn content as a result of mixing between eclogite-derived high-δ66Zn melt and peridotite-derived mantle-like δ66Zn melt. Our study provides a new model to reconcile the geochemical features of the Tarim continental flood basalts and highlights the potential role of decarbonated eclogite in the formation of continental flood basalts.","PeriodicalId":242264,"journal":{"name":"GSA Bulletin","volume":"332 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121596299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}