Yildirim Dilek

Miami University, Geology and Environmental Earth Science, Faculty Member

University College Cork, School of Biological Earth and Environmental Sciences (BEES), Faculty Member

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I am a University Distinguished Professor in Earth Sciences at Miami University, USA. My expertise is in the fields of structural geology, petrology-geochemistry and tectonics. I work on Phanerozoic and Precambrian orogenic belts around the world with a focus on ophiolites and suture zones, collision tectonics and magmatism, and extensional collapse of orogenic belts and attendant mafic-felsic magmatism. Recent field investigations include: Southern Tibet, Qinling Mountains, Chilean Patagonia, Northern Anatolia, and the Sierra Nevada Foothills (California).
Supervisors: Professor Eldridge M Moores; Professor Robert J Twiss; Professor James McClain
Phone: +1 (513) 529-2212

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Papers by Yildirim Dilek

An unrecognized development of retro-arc foreland basin system in northeast China during late Cretaceous (Campanian-Maastrichtian)

AGUFM, Dec 1, 2016

Corrigendum to “Structural architecture and stratigraphic record of Late Mesozoic sedimentary basins in NE China: Tectonic archives of the Late Cretaceous continental margin evolution in East Asia” [Earth Sci. Rev. 171 (2017) 598–620]

Earth-Science Reviews, Mar 1, 2018

Forearc Ophiolites: Archives of Subduction Initiation and Melt Evolution in Convergent Margin Settings

Acta Geologica Sinica - English Edition, 2015

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High-pressure metamorphism of Precambrian continental crust in the southwestern part of the Central Asian Orogenic Belt (South Kazakhstan and North Tien Shan) and tectonic implications for the evolution of the Palaeo-Asian Ocean

Geological Magazine

In this study, we investigated the high-pressure (HP) metamorphism of the Precambrian continental... more In this study, we investigated the high-pressure (HP) metamorphism of the Precambrian continental crust exposed in the Zheltau terrane in South Kazakhstan (Koyandy complex) and the Chu-Kendyktas terrane in the North Tien Shan of Kyrgyzstan (Aktyuz, Kemin and Kokdzhon complexes) within the SW part of the Central Asian Orogenic Belt. HP quartz–feldspar lithologies of the Koyandy complex consist of migmatized kyanite-bearing garnet–mica paragneisses, garnet–kyanite paragneisses and their derivatives associated with eclogites. Paragneisses demonstrate prograde evolution involving mica dehydration melting and producing magnesium-rich garnet, kyanite and K-feldspar at the near-peak to retrograde stages at pressures of 15–18.5 kbar and temperatures of 800–870°C. The widespread growth of micas in these rocks reflects lower stages of retrogression at P = 10–12 kbar and T = 720–770°C. The age distributions of the cores of detrital zircon grains from the paragneisses indicate a predominance of...

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$Research paper thumbnail of Geochemistry, mineral chemistry and Re–Os isotopes of refractory peridotites of the North Balkhash ophiolite zone in the West Central Asian Orogenic Belt (Central Kazakhstan): multi–stage melt evolution of a Late Precambrian forearc mantle$

Geochemistry, mineral chemistry and Re–Os isotopes of refractory peridotites of the North Balkhash ophiolite zone in the West Central Asian Orogenic Belt (Central Kazakhstan): multi–stage melt evolution of a Late Precambrian forearc mantle

Journal of the Geological Society

In this study we report on the petrography, major, trace element and mineral chemistry, platinum ... more In this study we report on the petrography, major, trace element and mineral chemistry, platinum group elements (PGE), and Re–Os isotope systematics of depleted ultramafic rock suites from the Itmurundy Block in the North Balkhash ophiolite zone (NBOZ) in Kazakhstan. Represented mainly by variably serpentinized harzburgites and dunites, our samples are characterized by low whole-rock Al2O3 (0.33–0.86 wt.%), CaO (0.51–0.86 wt%), and Na2O (0.07–0.25 wt.%) concentrations, and high-Mg olivine (Fo = 91–92) and orthopyroxene (Mg# = 92–93) contents, together with moderately high-Cr spinel numbers (Cr# = 63–68). They are depleted in incompatible elements (ΣREE, Nb, Sc) and enriched in compatible elements, such as Cr (up to 2817 ppm) and Ni (up to 2327 ppm), representing highly refractory mantle residues derived from a forearc mantle wedge. They underwent 19–23% hydrous partial melting to produce boninitic melts. 187Os/188Os values vary from 0.1202 to 0.12599, and 187Re/188Os ratios from 0.2...

Probing the foundation of the mid-Atlantic ridge

Eos, Transactions American Geophysical Union, 1995

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Detrital zircon U-Pb geochronology of Ediacaran siliciclastic carbonate rocks in eastern South China: Insights into the Precambrian assembly of the Yangtze and Cathaysia blocks

by Yildirim Dilek and Feng-Qi Zhang

Precambrian Research, 2025

The Cathaysia block, a composite terrane comprising West and East Cathaysia along the East Asian ... more The Cathaysia block, a composite terrane comprising West and East Cathaysia along the East Asian continental margin, forms a critical constituent of the South China block. Despite its tectonic significance, the timing of the Cathaysia-Yangtze amalgamation remains contentious, with proposed ages spanning from the Precambrian to the Mesozoic. We present integrated sedimentological and geochronological constraints derived from Ediacaran carbonate sequences in the Yuhang section of the southeastern Yangtze craton. Systematic analyses that combine sedimentary petrology with detrital zircon U-Pb-Hf isotopes reveal the following: (1) clastic components (30-45 % by volume) dominated by quartz exhibit a mixed siliciclastic carbonate rocks; (2) detrital zircon populations yield predominant Paleoproterozoic ages (2.0-1.75 Ga), showing remarkable similarities to the Precambrian basement of East Cathaysia, particularly through a characteristic age peak of 1.83-1.81 Ga; (3) Hf isotopic compositions demonstrate crustal residence ages that are indistinguishable from those of East Cathaysia sources. These convergent lines of evidence establish East Cathaysia as the primary sediment source for the southeastern Yangtze Ediacaran deposits. Consequently, we propose that the final amalgamation of the composite Cathaysia block with the Yangtze craton occurred during Precambrian crustal stabilization, fundamentally revising previous models that advocated for Phanerozoic accretion.

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Provenance of Cretaceous-Miocene sediments in Borneo: Implications for paleogeographic patterns and tectonic evolution

by Yildirim Dilek and Yi Yan

Earth-Science Reviews, 2025

Cretaceous-Miocene sedimentary rocks of northern Borneo contain a record of sediment routing link... more Cretaceous-Miocene sedimentary rocks of northern Borneo contain a record of sediment routing linked to subduction of the paleo-Paciﬁc and closure of the proto-South China Sea. How the sediment routing system responded to these changes continues to be debated, hindered by limited datasets. New Sr isotope data, combined with previous geochemical and chronological data, to determine the provenance of the Cretaceous- Miocene sediments in Borneo. Late Cretaceous-early Paleocene Lubok Antu Mélange, Lupar Formation, and Layar Member of the Rajang Group in Sarawak, central Borneo have low 87Sr/86Sr ratios and high ƐNd values and are dominated by Cretaceous detrital zircon grains. The results are consistent with sources from the collapsed Late Mesozoic magmatic belt on the Sunda Shelf. In the Paleocene-Eocene Kapit, Pelagus, Metah, and Bawang Members of the Rajang Group, there is a decrease in ƐNd values and an accompanying increase in Permian- Triassic and pre-Permian zircon ages. These trends imply that materials eroded from the Eastern Province of the Malay Peninsula became progressively more important to the Sarawak region after the early Paleocene. By contrast, to the east, Eocene strata in the Sabah region remain dominated by Cretaceous detrital zircons, sourced mainly from the Schwaner Mountains. Large numbers of Permian-Triassic detrital zircon ages in the Oligocene- middle Miocene strata of Sarawak and Sabah reﬂect a drainage network extending to older strata along the Malay Peninsula region since the late Eocene. These sources were cut off once South China Sea began to open, leaving the Schwaner Mountains and uplifted central Borneo as the dominant source of sediments in Sabah. The observed changes in sediment provenance between Sarawak in the west and Sabah in the east reﬂect changes in sediment routing that tracked subduction of the paleo-Paciﬁc plate and the progressive closure of the proto-South China Sea during the Late Cretaceous to middle Miocene.

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Late Tonian subduction to collisional tectonics in the southwestern Tarim Craton: Arc volcanism and sedimentary archives of terminal Rodinia amalgamation

by Yildirim Dilek and Hsuan-ying Chen

Precambrian Research, 2025

The southwestern margin of the Tarim Craton preserves signiﬁcant geological records related to th... more The southwestern margin of the Tarim Craton preserves signiﬁcant geological records related to the assembly and fragmentation of the Rodinia Supercontinent. However, its Neoproterozoic tectonic evolution remains debated, complicating the reconstruction of the Tarim Craton within the Rodinia framework. This study presents a multidisciplinary approach integrating stratigraphic, geochronological, geochemical, and provenance analyses of Tonian successions and tuffaceous interlayers to constrain the timing and mechanisms of contractional events in the southwestern Tarim Craton. The Tonian Silu Group shows a regressive succession from shallow marine to ﬂuvial-deltaic environments, capped by a regional unconformity beneath Cryogenian-Ediacaran strata. Tuffa-ceous interlayers suggest volcanic eruptions occurred between 802 Ma and 789 Ma, providing age constraints for the Sukuluoke Formation at the top of the Silu Group. These calc-alkaline tuffs exhibit arc-related geochemical signatures, suggesting continental arc magmatism along the southwestern margin of the Tarim Craton. Detrital zircon provenance and sedimentary facies analyses reveal that proximal Tonian magmatic arc clasts contributed signiﬁcantly to the basins, possibly sharing a common source with the volcanic tuff. These ﬁndings, along with regional magmatism, stratigraphic unconformities, and coeval metamorphism, collectively suggest a mid- Neoproterozoic assembly event involving subduction and collision. A plausible tectonic scenario involving subduction, collision, and subsequent rifting is proposed for the Neoproterozoic evolution of the southwestern Tarim Craton. This model serves as a preliminary framework that will require further geological constraints to reﬁne the regional geological history.

Geochemistry, geochronology, and Sr–Nd–Os isotopic compositions of early Permian maﬁc dykes in the Alxa Block and a new tectonomagmatic model for the evolution of the NW North China Craton

by Yildirim Dilek and Xiaolu Niu

Chemical Geology, 2025

Maﬁc dykes intruding continental crustal rocks preserve evidence for the isotopic and geochemical... more Maﬁc dykes intruding continental crustal rocks preserve evidence for the isotopic and geochemical composition of their melt source and hence the chemical makeup of the mantle beneath a continent. We have investigated the geochronology, geochemistry, and Sr–Nd–Os isotopes of recently discovered, Early Permian maﬁc dyke intrusions in the Alxa Block of the North China Craton to characterize the isotopic composition and evolution of the mantle underlying this continental block. SHRIMP U–Pb dating results reveal that maﬁc dykes in the Yamaitu area in eastern Alxa are 292 ± 4 Ma in age, whereas those in the Beidashan area in western Alxa are 280 ± 2 Ma in age. The Yamaitu dykes consist mainly of basalt to trachy-basalt (SiO2 = 52.61–53.01 wt%), belong to the medium-K to high-K calc-alkaline series, and show crust-like rare earth element and trace element patterns and enriched εNd(t) values (􀀁 5.8 to 􀀁 5.6), and initial 87Sr/86Sr ratios of 0.7073 to 0.7074. In comparison, the Beidashan dykes in the west consist of basalt to basaltic andesite (SiO2 = 50.16 to 57.83 wt%) and belong to medium-K calc-alkaline series, characterized by lesser enrichment in large ion lithophile elements, but depletion in Nb, Ta, Zr, Hf contents, as well as in their εNd(t) values (􀀁 1.3 to +3.1) and initial 87Sr/86Sr ratios (0.7051 to 0.7068). Our Os isotopic data reveal that crustal contamination of the magmas of these dyke intrusions was limited to less than 5 %. These geochemical features and contrasting Sr–Nd isotopic compositions of the analyzed maﬁc dykes reﬂect a heterogenous mantle source beneath the Alxa Block containing an enriched subcontinental lithospheric mantle (SCLM) as well as a depleted mantle, both of which were variously modiﬁed by subduction-derived melts and ﬂuids. In light of our new ﬁndings on the nature of the Early Permian composition of the SCLM beneath the Alxa Block, we have also examined in this study the extant data on geochronological, and geochemical–isotopic data from the early and middle Paleozoic granitoids in the Alxa Block in order to decipher their diverse melt origins within the geodynamic framework of the northwestern part of the North China Craton (NCC). Based on our synthesis of the magmatic evolution of the Paleozoic–Early Mesozoic intrusions in the Alxa Block, we present a new tectonic model for the crustal evolution of the Alxa Block and of the NW part of the North China Craton, involving a southward subduction of a Paleo-Asian Ocean (PAO) seaway beneath the Alxa Block during the Ordovician through Silurian, a collision of the Alxa and the South Mogolian Blocks since the Early Devonian, and an extensional tectonic regime for the Alxa Block during the Early Carboniferous through Permian time.

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$Research paper thumbnail of Iron isotopic fractionation during seafloor hydrothermal alteration of oceanic upper crust, as recorded in the Geotimes lavas of the Semail ophiolite, Oman$

Iron isotopic fractionation during seafloor hydrothermal alteration of oceanic upper crust, as recorded in the Geotimes lavas of the Semail ophiolite, Oman

Chemical Geology, 2025

The Semail ophiolite in Oman features a crustal stratigraphy akin to a fast-spreading modern ocea... more The Semail ophiolite in Oman features a crustal stratigraphy akin to a fast-spreading modern oceanic lithosphere. Its Geotimes pillow lavas, the stratigraphically oldest extrusive sequence at the bottom, share geochemical traits with contemporary mid-ocean ridge basalts, offering a unique opportunity to examine iron (Fe) isotopic fractionation during hydrothermal alteration under varied redox conditions. Signiﬁcant alteration transformed primary minerals, evidenced by the dissolution of clinopyroxene, plagioclase, and ilmenite, alongside the pre-cipitation of chlorite, albite, and magnetite-hematite. The 87Sr/88Sr ratios of 18 basalt subsamples from altered pillow lava range from 0.705110 to 0.705680, indicating extensive seawater interaction. The δ56Fe values show systematic variations at a centimeter scale (0.037–0.291 ‰), primarily resulting from hydrothermal processes rather than source inheritance. Notably, the pillow lava’s core displays higher δ56Fe values, suggesting the initial dissolution of Fe-bearing minerals under reduced conditions. In contrast, the edges show lower δ56Fe values akin to mean mid-ocean ridge basalt, indicating that strong oxidation conditions minimally affected these isotopic values. In conclusion, this study reveals the complex variations of the Fe concentrations and Fe isotopic compositions of altered basalt that suffered hydrothermal alteration during the various redox conditions.

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Metamorphism during Alpine Crustal Thickening and Extension in Central Anatolia, Turkey: the Nigde Metamorphic Core Complex

Journal of Petrology, Jul 1, 1998

The Nig ˘de massif, a metamorphic core complex in Central Anatolia high-temperature reactions can... more The Nig ˘de massif, a metamorphic core complex in Central Anatolia high-temperature reactions can obliterate assemblages (Turkey), contains petrologic evidence for the transition from Alpine formed during earlier, lower-temperature phases of metacrustal thickening to extension and exhumation of high-grade midmorphism. This can hinder use of petrologic information crustal rocks. Sillimanite-potassium feldspar gneiss formed and to interpret tectonic processes. If reaction textures are partially melted during Barrovian metamorphism and records maxpreserved, however, rocks may record a range of presimum conditions of 5-6 kbar, >700°C. The two-mica U ¨c ¸kapılı sure-temperature conditions from their prograde and/ granite and a related dike suite intruded the migmatitic metapelitic or retrograde paths and a more complete picture of the rocks, forming a contact aureole that contains andalusite and tectonic evolution of a terrane can be reconstructed. Of cordierite. These low-pressure minerals indicate that crustal thickparticular interest are the mechanisms and timing of ening was followed by exhumation of mid-crustal rocks to relatively transition from contraction to extension and the acshallow depths (<10 km) at lower temperatures before the emcompanying exhumation of middle-to lower-crustal placement of granitic magma. Formation of andalusite was followed rocks. The present study describes a medium-pressure, by a second, prograde episode of sillimanite growth during lowhigh-temperature terrane (the Nig ˘de massif; Fig. ) in pressure-high-temperature metamorphism in the central part of the central Anatolia, Turkey, that developed as a metamassif, where magmatism was most extensive. A generalized P-T morphic core complex in response to Alpine crustal path for the highest grade rocks therefore consists of an initial thickening. Metamorphic rocks in the central, high-grade clockwise path with a late thermal spike and characterizes burial part of the massif record in their mineral assemblages, and subsequent exhumation accompanied by magmatism. reaction textures, and structures the processes of burial, exhumation, and accompanying magmatism.

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A Newly Identified “Proto‐Kenting Mélange (S. Taiwan)” Represents a Missing Link for a Continuous Early Cretaceous Paleo–Pacific Subduction–Accretion System

Tectonics, 2025

Most mélanges in exhumed subduction‐accretion complexes are polygenetic, recording significant in... more Most mélanges in exhumed subduction‐accretion complexes are polygenetic, recording significant information about the nature of geological processes during their formation. Here, we apply micro‐chemical analysis and illite K‐Ar dating to constrain the deformation mechanism and timing of the pervasively sheared scaly matrix in the accretionary complex rocks presently known as “Kenting Mélange” in the Hengchun Peninsula (South Taiwan). Our results reveal that parts of the matrix were formed in Cretaceous (96.7 ± 8.6 Ma and 108 ± 18.4 Ma) due to pressure solution. These new, older matrix ages suggest that the Kenting Mélange, which was considered as Cenozoic and interpreted to have been associated with the subduction of the South China Sea, preserves different primary chaotic units (e.g., mélange and/or olistostrome). Our findings imply the Kenting Mélange is actually polygenetic and allow part of Kenting Mélange that we named the “proto‐Kenting Mélange” to be interpreted as a remnant of a primary mélange, which was mixed and/or juxtaposed in the Cenozoic Kenting Mélange. The block‐in‐matrix fabric with a pervasively sheared scaly muddy matrix, along with the preservation of slightly older oceanic crust blocks, suggests that the proto‐Kenting Mélange is most likely an ocean plate stratigraphy mélange. This unit initially formed near a Paleo‐Pacific subduction margin during the latest Early Cretaceous. Our results reveal a nearly 3000‐km‐long physical archive of latest Early Cretaceous subduction–accretion processes, which took place adjacent to the continental margin of East Asia during the consumption of Paleo–Pacific ocean floor during the latest Mesozoic.

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Spatial-temporal evolution of the source-to-sink system in the early and mid-Cretaceous Songliao Basin, Northeast China, and its constraints on basin prototype boundaries and paleogeography

Palaeogeography, Palaeoclimatology, Palaeoecology, 2025

The Songliao Basin, the largest hydrocarbon basin in Northeast China, features exceptionally well... more The Songliao Basin, the largest hydrocarbon basin in Northeast China, features exceptionally well-preserved Cretaceous stratigraphic sequences. The evolution of its source-to-sink system provides critical insights into the basin prototype boundaries, paleogeography, and the tectonic evolution of the East Asian margin. Our investigation concentrated on detrital zircon U-Pb dating of sandstones from the Quantou Formation in the Binxian area of the northeastern Songliao Basin. We also synthesized our findings with available data, analyzing 2469 detrital zircon U-Pb ages from 35 sandstone samples spanning the Shahezi to Quantou formations across the basin. This integrated approach enabled a detailed reconstruction of the evolution of the source-to-sink system and its implications for basin prototype boundaries during the early to mid-Cretaceous period. This transformation shifted from a proximal, relatively independent system in the early Cretaceous to a distal, longdistance transport system in the mid-Cretaceous. This transition indicates the evolution of the basin from a collection of relatively isolated small to medium-sized graben and half-graben basins into a unified, large-scale sag basin. This transformation was initiated in the third member of the Denglouku Formation (ca. 100 Ma) and stabilized in the third member of the Quantou Formation (ca. 95 Ma). During this period, the eastern boundary of the basin experienced significant eastward expansion. Initially located between the Yilan-Yitong Fault and the Dunhua-Mishan Fault during the deposition of the Denglouku Formation, it extended toward the Yalu River Fault or the Rangnim Block in the Korean Peninsula during the deposition of the Quantou Formation. Our findings also suggest the development of an extensive coastal mountain along the East Asian margin during the mid-Cretaceous, stretching from eastern South China through eastern North China to the Korean Peninsula.

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Serpentinites of the Pollino ophiolite massif (Calabria, southern Italy), mineralogy, petrography and future perspectives

by Yildirim Dilek and Dichicco Maria Carmela

Periodico di Mineralogia, 2024

Serpentinites of the Pollino ophiolite Massif have been widely studied for their mineralogical, p... more Serpentinites of the Pollino ophiolite Massif have been widely studied for their mineralogical, petrographic, and chemical characteristics, providing major findings on their impact on environmental and human health issues. The mineralogy and the petrography of the studied serpentinites revealed the presence of lizardite, antigorite, crysotile, Cr-chlorite, magnetite, tremolite, actinolite, pyroxene, calcite, dolomite, aragonite, and talc, and the most commonly occurring minerals are different polymorphs of serpentine. Capturing atmospheric CO2 and storing it in natural rock systems through carbonation reactions is a promising greenhouse gas mitigation research, and largely depends on the use of hydrated ultramafic rocks, which are widespread in orogenic belts around the globe. The integration between petrographic and mineralogical studies of serpentinites in Southern Italy ophiolites can represent a starting point for the study of natural materials, which can be used for CO2 storage and sequestration. A particular attention must be given to those carbonate phases that are produced by carbonation processes to check whether the serpentinites of the Pollino Massif can be used for the induced mineral Carbon Capture Storage (CCS). If successful, this technique and the Pollino Massif serpentinites can become highly significant in safeguarding the health of our planet’s climate.

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Multiple episodes of late Neoproterozoic rifting in the Tarim Craton during its separation from the supercontinent Rodinia

by Yildirim Dilek and Hongxiang Wu

Journal of the Geological Society, London, 2024

In this paper, we review and evaluate the magmatic history, regional stratigraphy, structural pat... more In this paper, we review and evaluate the magmatic history, regional stratigraphy, structural patterns and sedimentary provenance features of the Late Neoproterozoic Tarim Craton to elucidate the nature and different modes of extensional tectonics during the Latest Neoproterozoic, a critical time coinciding with the disintegration of the supercontinent Rodinia. New detrital zircon U-Pb ages and geochemical data acquired from quartz schists and spatially associated granites in the Tugerming anticline along the northern margin of the Tarim Craton have revealed Cryogenian ages, as opposed to Early Neoproterozoic and older ages as reported in previous studies. Granitic intrusions are dated at 656-637 Ma, which involved remelting of the ancient crust following the decline of the initial (Cryogenian) rift stage. They are unconformably overlain by terrestrial clastic deposits. Based on the available detrital zircons from the Late Neoproterozoic sedimentary rock assemblages, we identify a major change in the provenance of the basinal strata at the end of the Cryogenian period. This inferred provenance change, associated with basement exhumation, overlaps in time with resumed magmatic activities, basin inversion and uplift along the northern margin of the craton. The initial, Cryogenian rifting stage was facilitated by pure shear deformation that produced rift basins in and across the Tarim Craton. The subsequent rifting stage was facilitated by simple shear deformation, confined to the northern edge of the craton as the break-up of the supercontinent Rodinia further progressed. Episodic rifting of the Tarim Craton and its separation from Rodinia were aided by thermal weakening of its lithosphere owing to the periodic impingement of mantle upwelling beneath it throughout the Cryogenian and Ediacaran periods.

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Tracking multiple stages of serpentinization processes of the Yarlung Zangbo Suture Zone peridotites in southern Tibet: Implications for the tectonic evolution of the Neotethyan oceanic lithosphere

Geological Society of America Bulletin, Oct 15, 2023

Serpentinites are key repositories of fluid-mobile elements (FMEs) in subduction zones and record... more Serpentinites are key repositories of fluid-mobile elements (FMEs) in subduction zones and record significant information about the origin and geodynamic evolution of oceanic lithosphere. Here, we report on the structural textures and mineralogical compositions of different types of serpentinites collected from the central segment of the Yarlung Zangbo Suture Zone in southern Tibet and present their bulk-rock and mineral chemistry, and Sr isotopic compositions. The main textures include massive, scaly, and gouge serpenti-nites exposed in the Ngamring and Sangsang ophiolites. Bulk-rock Al2O3/SiO2 and spinel Cr# values suggest that the Ngamring serpen-tinites originally formed in an abyssal setting, whereas the Sangsang serpentinites devel-oped initially in a forearc mantle. Both serpentinite assemblages were subsequently incorporated into a subduction plate interface as subducted serpentinites. Massive serpentinites preserve the geochemical fingerprint of original serpentinized fluids in mid-oceanic ridge to forearc settings, whereas sheared serpentinites with scaly and gouge textures are reset in their Sr isotopic compositions and FME ratios (i.e., Cs/U, Li/U, and Rb/U) due to their reactions with slab-derived flu-ids. Scaly and gouge types of the Ngamring serpentinites have lower 87Sr/86Sr values (87Sr/86Sr = 0.7081–0.7082) and higher alkali element–U ratios (i.e., Cs/U, Li/U, and Rb/U) than those of the massive serpentinite types (87Sr/86Sr = 0.7091–0.7096), which indicates that they interacted with fluids at a slab interface after their initial seafloor serpentinization. In contrast, the massive Sangsang serpentinites display lower 87Sr/86Sr values (87Sr/86Sr = 0.7041–0.7043, similar to those of the Yarlung Zangbo ophiolites) and higher alkali element–U ratios than those of the sheared serpentinites (87Sr/86Sr = 0.7063–0.7087). These findings point to the significant role of the increased influx of subducted sediment-derived fluids within subduction shear zones in further affecting the serpentinization fingerprint. This study demonstrates that serpentinites with different textural, geochemical, and isotopic features within the same suture zone may represent the serpentinization products in different tectonic environments during the seafloor spreading, subduction initiation, and subduction zone evolution of oceanic lithosphere.

Tectonic switch from Triassic contraction to Jurassic-Cretaceous extension in the western margin of the Tarim Basin, Northwest China: New insights into the evolution of the paleo-Tethys Orogenic Belt

AGU Fall Meeting Abstracts, Dec 1, 2020

We use stratigraphic, sedimentological, and borehole data and seismic profiles from the western T... more We use stratigraphic, sedimentological, and borehole data and seismic profiles from the western Tarim Basin to document its Mesozoic tectonic evolution. A nearly 60-km-wide, Triassic fold-and-thrust belt along the southwestern margin of Tarim Basin is unconformably overlain by a Jurassic-Cretaceous sedimentary sequence along a regional angular unconformity. The Lower-Middle Jurassic strata consist mainly of an upward-fining sequence ranging from terrestrial conglomerates to turbidite deposits, which represent the products of an initial rift stage. Palaeocurrent analyses show that sediments for these rift deposits were derived from the paleo-Kunlun and paleo-Tienshan Mountains to the southwest and northern, respectively. The overlying Upper Jurassic-Cretaceous series consist of coarse-grained, alluvial fan to braided river deposits in the lower stratigraphic member, and lagoonal mudstones and marine carbonates in the upper member. These finer-grained rocks were deposited in a subsiding basin, indicating that a significant change and reorientation in the drainage system should have occurred within the basin during the Early Cretaceous. The western Tarim Basin evolved from a syn-rift stage to a post-rift stage during the Jurassic-Cretaceous. A post-orogenic stretch developed due to the evolution of the Paleo-Tethyan orogenic belt in Central Asia is a likely geodynamic mechanism for this major tectonic switch from a contractional episode in the Triassic to an extensional deformation phase in the Jurassic-Cretaceous.

Kalaymyo Peridotite Massif in the Indo-Myanmar Ranges (Western Myanmar): Its Mineralogy, Geochemistry and Tectonic Implications

GSA Annual Meeting in Seattle, Washington, USA - 2017, 2017

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Accretionary Prism Formation in Oblique Subduction Zones: Comparative Study in Space and Time

GSA Annual Meeting in Seattle, Washington, USA - 2017, 2017

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