Yildirim Dilek
Miami University, Geology and Environmental Earth Science, Faculty Member
- I am a University Distinguished Professor in Earth Sciences at Miami University, USA. My expertise is in the fields o... moreI 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).edit
Mesozoic magmatic rocks occur widely in the South China Block and are generally interpreted as the manifestations of the subduction of the Paleo-Pacific oceanic lithosphere beneath Asia. Subduction-driven magmatism in southeast (SE) China... more
Mesozoic magmatic rocks occur widely in the South China Block and are generally interpreted as the manifestations of the subduction of the Paleo-Pacific oceanic lithosphere beneath Asia. Subduction-driven magmatism in southeast (SE) China continued from the Late Permian through the Late Cretaceous with an inferred lull between 125 Ma and 115 Ma that is known in the literature as the Cretaceous ‘‘magmatic quiescence”. We report in-situ zircon U–Pb ages, Hf–O and whole-rock Sr–Nd iso-topes, and whole-rock geochemistry of Cretaceous granitoids on Hainan Island and discuss their magmatic evolution within the framework of the Late Mesozoic geodynamics of SE China. We recognize two main stages of the emplacement of Cretaceous granitoids on Hainan, first around 120 Ma and then around 100–95 Ma, displaying high-K calc-alkaline, I-type geochemical affinities. Granites in both age groups are enriched in LILE and LREE, but depleted in Nb, Ta, Ba, Sr, and Eu. The 120 Ma granites have zircon EpsilonHf(t) values of –2.6 to 2.3 corresponding to Hf crustal model ages, ranging from 0.79 Ga to 1.03 Ga, and Delta18O values ranging from 6.9‰ to 7.7‰. Zircons from 100–95 Ma granites have EpsilonHf(t) values of –4.2 to 1.1 corresponding to Hf crustal model ages of 1.08 Ga to 1.42 Ga, and d18O values ranging from 6.7‰ to 8.4‰. Increasing EpsilonHf(t) values of the Cretaceous Hainan granites with younger crystallization ages indicate addition of more juvenile components and reworking of crustal material into their melt evolution. The eNd(t) values of the 120 Ma and 100–95 Ma granitoids range between –4.1 to –0.4 and –7.7 to –4.0, respectively. The calculated two–stage model age of the 100–95 Ma granitoids clusters between 1.25 Ga and 1.53 Ga. These isotopic data suggest that magmas of the Cretaceous granitoids were produced by partial melting of Mesoproterozoic metabasaltic rocks, which make up much of the crystalline basement of the southern Cathaysia block. The geochemical and isotopic characteristics of the Cretaceous granitoids on Hainan resemble those of magmatic arcs in the Circum–Pacific orogenic belts and identical to those of nearly coeval granitoid intrusions in the continental fragments within the South China Sea basin. We interpret these Cretaceous granitoids in the Peri–South China Sea region as the remnants of a once contiguous Late Mesozoic magmatic arc system that bounded the southern margin of the entire continental Southeast Asia. Our findings do not support the existence of an episode of magmatic quiescence in the geological record of SE China during the Aptian.
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We investigate in this paper mineral compositions and geochemical evolution of the mantle wedge peridotites preserved in the Late Cretaceous Zagros ophiolites of SW Iran. Mantle peridotites above subduction zones commonly experience... more
We investigate in this paper mineral compositions and geochemical evolution of the mantle wedge peridotites preserved in the Late Cretaceous Zagros ophiolites of SW Iran. Mantle peridotites above subduction zones commonly experience distinct melting, depletion and refertilization processes as a result of the circulation of fluids derived from subducting slabs and flux melting. Our results reveal that the mantle wedge peridotites in the Zagros ophiolites are characterized mainly by residual and impregnated types. Residual peridotites resulted from early depletion and later refertilization processes, whereas impregnated peridotites developed due to episodic melt impregnations within and across the mantle. Mg#s and NiO contents, spinel Cr#, Mg#, and TiO2 in olivines, Mg# and Al2O3 contents of orthopyroxenes, and Mg#, TiO2 and Al2O3 contents in clinopyroxenes of dunites, harzburgites and lherzolites indicate the significant role of re-equilibration processes among different mineral phases and interactions with basaltic melts percolating within the host peridotites. The observed geochemical variations in the mineral chemistry of the Zagros peridotites reflect changes in magma chemistry and fluctuations in the degree of melt extraction and melt–rock interactions within the mantle peridotites. However, our data suggest that Mg–Fe distribution in the spinels of some dunites and harzburgites might also have resulted from subsolidus redistribution and exchange with surrounding olivine grains. Spinel and clinopyroxene phases in gabbroic rocks and ultramafic cumulates within the Zagros ophiolites also show significant variations in their compositions, suggesting that their magmas evolved from MORB-like to IAT, calc–alkaline and boninite suites, typical of subduction initiation-generated melts. Hence, the Zagros ophiolites present a case study of time-progressive melt evolution of the forearc oceanic lithosphere.
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We present new U-Pb detrital zircon ages, depositional history and tectonic model for the Liuqu Conglomerate (LQC) in southern Tibet that represents a critical geochronometer for the collision history of the Tibetan-Himalayan Orogenic... more
We present new U-Pb detrital zircon ages, depositional history and tectonic model for the Liuqu Conglomerate (LQC) in southern Tibet that represents a critical geochronometer for the collision history of
the Tibetan-Himalayan Orogenic Belt. LQC is a ∼5 km–thick, late Mesozoic–Cenozoic molasse deposit occurring strictly within the Yarlung Zangbo Suture Zone (YZSZ) and is tectonically overlain to the north
by the Cretaceous Xigaze ophiolite and to the south by the Mesozoic Tethyan Himalaya sequence. It consists of matrix- and clast-supported conglomerates with sandstone intercalations, and its matrix includes poorly to moderately sorted sandstone and mudstone. New U–Pb detrital zircon dating of LQC sandstones has revealed a youngest zircon age of 307 ± 13 Ma and an oldest zircon age of 3362 ± 51 Ma. The age spectrum of zircons displays a prominent peak of ∼935 Ma, two large peaks at ∼516 Ma and 1474 Ma, and two small clusters of ∼2429 Ma and ∼2772 Ma that point to East Gondwana as the likely provenance for the LQC depocenter. The LQC represents fluvial deposits of an axial river system, which developed in an orogen-parallel, transtensional accommodation space within the YZSZ, after the collision of the Late Jurassic-Early Cretaceous Trans–Tethyan arc–trench system with the northern edge of India in the latest Cretaceous. The Indian subcontinent with the accreted Tethyan ophiolites and the intra–suture LQC depocenter arrived at and collided with the active margin of Eurasia during the latest Oligocene (∼23 Ma). The LQC depocenter started receiving clastic material and zircons for the first time from the Gangdese Magmatic Belt and the Xigaze forearc basin to the north by ∼20 Ma. The ensuing continent–continent collision resulted in significant crustal uplift across the collision zone, and in the inversion and rapid exhumation of the LQC strata by the early–Middle Miocene. The depositional and exhumation history of the fluvial LQC formation within the YZSZ involved two discrete collision events during the evolution of the Tibetan-Himalayan Orogenic system.
the Tibetan-Himalayan Orogenic Belt. LQC is a ∼5 km–thick, late Mesozoic–Cenozoic molasse deposit occurring strictly within the Yarlung Zangbo Suture Zone (YZSZ) and is tectonically overlain to the north
by the Cretaceous Xigaze ophiolite and to the south by the Mesozoic Tethyan Himalaya sequence. It consists of matrix- and clast-supported conglomerates with sandstone intercalations, and its matrix includes poorly to moderately sorted sandstone and mudstone. New U–Pb detrital zircon dating of LQC sandstones has revealed a youngest zircon age of 307 ± 13 Ma and an oldest zircon age of 3362 ± 51 Ma. The age spectrum of zircons displays a prominent peak of ∼935 Ma, two large peaks at ∼516 Ma and 1474 Ma, and two small clusters of ∼2429 Ma and ∼2772 Ma that point to East Gondwana as the likely provenance for the LQC depocenter. The LQC represents fluvial deposits of an axial river system, which developed in an orogen-parallel, transtensional accommodation space within the YZSZ, after the collision of the Late Jurassic-Early Cretaceous Trans–Tethyan arc–trench system with the northern edge of India in the latest Cretaceous. The Indian subcontinent with the accreted Tethyan ophiolites and the intra–suture LQC depocenter arrived at and collided with the active margin of Eurasia during the latest Oligocene (∼23 Ma). The LQC depocenter started receiving clastic material and zircons for the first time from the Gangdese Magmatic Belt and the Xigaze forearc basin to the north by ∼20 Ma. The ensuing continent–continent collision resulted in significant crustal uplift across the collision zone, and in the inversion and rapid exhumation of the LQC strata by the early–Middle Miocene. The depositional and exhumation history of the fluvial LQC formation within the YZSZ involved two discrete collision events during the evolution of the Tibetan-Himalayan Orogenic system.
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The young Taiwan orogenic belt is a classic example of a modern arc–continent convergence zone, which displays a longitudinal transition from active collision in the north to oceanic subduction in the south. However, the timing of its... more
The young Taiwan orogenic belt is a classic example of a modern arc–continent convergence zone, which displays a longitudinal transition from active collision in the north to oceanic subduction in the south. However, the timing of its initial exposure above the sea level and the early-stage uplift mechanism has been a point of much debate. Here we applied major and trace element, Nd isotope and heavy minerals analysis on the Miocene
sedimentary rocks from the Hengchun Peninsula to trace sediment provenance and to further constrain the tectonic-sedimentary evolution of the Taiwan accretionary prism. Results show that the Hengchun mudstones (~11.6–6.5 Ma) are characterized by higher CaO (1.42 wt %) and MgO (2.57 wt %) contents, Cr/Zr (0.52) and Co/Th (1.58) ratios, and less negative ϵNd (t) values (-12 to -7) than those from the Chinese passive continental margin sediments. It indicates that the Chinese mainland was not exclusive sediment contributor for the Hengchun sediments. Combined with the high content of Cr-spinel heavy mineral (mean value ~ 28.2%) in the Hengchun Miocene sandstones, and the presence of mafic lithic grains and N-MORB-type mafic rocks of 26-22 Ma in the Hengchun Peninsula, it is clear that the subducting South China Sea oceanic lithosphere should be also considered for the origin of the Hengchun sediments. The most likely source of these oceanic clasts being transported to the Hengchun Peninsula is the equivalent prism to the north, which had involved oceanic fragments during the subduction process. Consequently, Taiwan accretionary prism should have been already partly exposed prior to ~11.6 Ma, considerably earlier than most previous estimates and the onset of arc-continent collision. Underplating of seamounts and/or the thinned Chinese continental margin beneath the overlying Taiwan accretionary prism, together with wedge extrusion tectonics, may have played an important role for this early-stage uplift, which now is also observed in the sandbox experiments, marine observation and analogue modeling. Our study not only better integrates the subduction and then erosion history of the South China Sea oceanic crust with sedimentary records in Taiwan, but also signifies a modern example from Taiwan that highlights the importance of soft exhumation mechanism in worldwide plate convergence zones relative to hard collision.
sedimentary rocks from the Hengchun Peninsula to trace sediment provenance and to further constrain the tectonic-sedimentary evolution of the Taiwan accretionary prism. Results show that the Hengchun mudstones (~11.6–6.5 Ma) are characterized by higher CaO (1.42 wt %) and MgO (2.57 wt %) contents, Cr/Zr (0.52) and Co/Th (1.58) ratios, and less negative ϵNd (t) values (-12 to -7) than those from the Chinese passive continental margin sediments. It indicates that the Chinese mainland was not exclusive sediment contributor for the Hengchun sediments. Combined with the high content of Cr-spinel heavy mineral (mean value ~ 28.2%) in the Hengchun Miocene sandstones, and the presence of mafic lithic grains and N-MORB-type mafic rocks of 26-22 Ma in the Hengchun Peninsula, it is clear that the subducting South China Sea oceanic lithosphere should be also considered for the origin of the Hengchun sediments. The most likely source of these oceanic clasts being transported to the Hengchun Peninsula is the equivalent prism to the north, which had involved oceanic fragments during the subduction process. Consequently, Taiwan accretionary prism should have been already partly exposed prior to ~11.6 Ma, considerably earlier than most previous estimates and the onset of arc-continent collision. Underplating of seamounts and/or the thinned Chinese continental margin beneath the overlying Taiwan accretionary prism, together with wedge extrusion tectonics, may have played an important role for this early-stage uplift, which now is also observed in the sandbox experiments, marine observation and analogue modeling. Our study not only better integrates the subduction and then erosion history of the South China Sea oceanic crust with sedimentary records in Taiwan, but also signifies a modern example from Taiwan that highlights the importance of soft exhumation mechanism in worldwide plate convergence zones relative to hard collision.
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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... 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 Neoproterozoic and minor occurrence of Mesoproterozoic and Palaeoproterozoic sources of their protoliths. The ages of ~487–485 Ma obtained from the zircon rims of the paragneisses reflect the timing of their HP metamorphic re-equilibration. These age clusters are consistent with the age estimates obtained from the rims of zircons in the eclogite-bearing garnet gneisses of the adjacent Aktyuz complex in the North Tien Shan. The P–T paths and zircon ages obtained from the high-grade quartz–feldspar gneisses of the Zheltau and Chu-Kendyktas terranes are thus interpreted to indicate involvement of the crustal material derived from the Precambrian basement (magmatic zircons aged ca. 844 Ma) and its Ediacaran–Cambrian sedimentary cover (detrital zircons with maxima at 1 Ga and 800–600 Ma) in the latest Cambrian subduction processes induced by the closure of the oceanic basins assigned to the Palaeo-Asian Ocean.
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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... 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.
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By quantifying the deposition of Asia-derived dust in the Western Pacific Ocean it is possible to constrain the consequences of climate change in East Asia. However, the rates of eolian dust deposition and its transport mechanism in the... more
By quantifying the deposition of Asia-derived dust in the Western Pacific Ocean it is possible to constrain the consequences of climate change in East Asia. However, the rates of eolian dust deposition and its transport
mechanism in the low-latitude Pacific remain uncertain. Core CP19 recovered sediment dating from ~1 Ma to the present in the Parece Vela Basin (PVB). In this study we present bulk-rock major and trace element
geochemistry, and Sr and Nd isotopic compositions from this sediment. The results reveal that these clastic sediments are a mixture of volcanic materials derived from the adjacent island arcs and eolian dust material
originating from the arid regions of East Asia. Within the PVB, the proportion of Asian dust in the detrital sediment ranges from 30% to 50%, with an average of 44%. The majority of the dust originated from Eastern
Asian deserts. Sr and Nd isotopes indicate that there is a significant increase in the overall proportion of eolian dust in the PVB starting at ~0.64 Ma, influenced by an enhanced East Asian winter monsoon. In contrast, strengthening of the East Asian summer monsoon led to a decrease in the proportion of the eolian dust from the Ordos deserts. The notable alteration in eolian dust flux to the PVB corresponds to an abrupt intensification of aridity and monsoon climate in the East Asian continent at ~0.64 Ma, caused by the Middle Pleistocene Climate Transition.
mechanism in the low-latitude Pacific remain uncertain. Core CP19 recovered sediment dating from ~1 Ma to the present in the Parece Vela Basin (PVB). In this study we present bulk-rock major and trace element
geochemistry, and Sr and Nd isotopic compositions from this sediment. The results reveal that these clastic sediments are a mixture of volcanic materials derived from the adjacent island arcs and eolian dust material
originating from the arid regions of East Asia. Within the PVB, the proportion of Asian dust in the detrital sediment ranges from 30% to 50%, with an average of 44%. The majority of the dust originated from Eastern
Asian deserts. Sr and Nd isotopes indicate that there is a significant increase in the overall proportion of eolian dust in the PVB starting at ~0.64 Ma, influenced by an enhanced East Asian winter monsoon. In contrast, strengthening of the East Asian summer monsoon led to a decrease in the proportion of the eolian dust from the Ordos deserts. The notable alteration in eolian dust flux to the PVB corresponds to an abrupt intensification of aridity and monsoon climate in the East Asian continent at ~0.64 Ma, caused by the Middle Pleistocene Climate Transition.
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Research Interests: Earth Sciences, Geology, Geochemistry, Precambrian, Rodinia, and 5 moreOrogeny, Metamorphism, Zircon, Supercontinent, and Craton
Research Interests: Geology, Geophysics, Seismology, Cenozoic, COLLISION, and 4 moreMagmatism, Tearing, Lithosphere, and Slab
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Research Interests: Earth Sciences, Geology, Paleontology, Precambrian, Rodinia, and 4 moreRIFT, Paleozoic, Unconformity, and Tarim Basin
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The Kazdağı metaophiolite crops out in the Kazdağı (Ida) Mountains in the Biga Peninsula in northwestern Turkey. It is in stratigraphic contact with the high–grade metamorphic rocks of the Kazdağı Massif. Metaophiolitic and high–grade... more
The Kazdağı metaophiolite crops out in the Kazdağı (Ida) Mountains in the Biga Peninsula in northwestern Turkey. It is in stratigraphic contact with the high–grade metamorphic rocks of the Kazdağı Massif. Metaophiolitic and high–grade metamorphic rocks are tectonically overlain by low–grade metamorphic units of the Permo‐Triassic Karakaya Complex of the Sakarya Zone. Late Oligocene‐Early Miocene granites intruded these tectonic units (Okay and Satır, 2000; Duru et al. 2012).In the Kazdağı metaophiolitic sequence, upper mantle peridotites are represented by metaharzburgite and metadunite, whereas the mantle transition zone metaperidotites are composed of metadunite, metapyroxenite and minor plagioclase‐bearing metalherzolite. The upper part of the metadunites in the mantle transition zone show intercalation with metagabbros. Gabbros of oceanic crust experienced amphibolite facies metamorphism and are transformed into amphibolite, garnet amphibolite and migmatitic gabbros. The metagab...
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He Pozanti‐Karsanti ophiolite (PKO) is one of the largest oceanic remnants in the Tauride belt, Turkey. Micro‐diamonds were recovered from the podiform chromitites, and these were investigated based on morphology, color,... more
He Pozanti‐Karsanti ophiolite (PKO) is one of the largest oceanic remnants in the Tauride belt, Turkey. Micro‐diamonds were recovered from the podiform chromitites, and these were investigated based on morphology, color, cathodoluminescence, nitrogen content, carbon and nitrogen isotopes, internal structure and inclusions. The diamonds recovered from the PKO are mainly mixed‐habit diamonds with sectors of different brightness under the cathodoluminescence images. The total δ13C range of the PKO diamonds ranges between −18.8 ‰ and −28.4 ‰, with a principle δ13C mode at −25 ‰. Nitrogen contents of the diamonds range from 7 to 541 μg/g with a mean value of 171 μg/g, and the δ15N values range from −19.1 ‰ to 16.6 ‰, with a δ15N mode of −9 ‰. Stacking faults and partial dislocations are commonly observed in the Transmission Electron Microscopy foils whereas inclusions are rather rare. Combinations of (Ca0.81Mn0.19)SiO3, NiMnCo‐alloy and nano‐size, quenched fluid phases were observed as i...
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We report new U–Pb zircon age data, zircon in situ oxygen isotope, mineral chemistry, whole-rock geochemistry and Sr–Nd isotopic compositions from the Early Devonian ultrapotassic Gucheng pluton in the North China Craton, and discuss its... more
We report new U–Pb zircon age data, zircon in situ oxygen isotope, mineral chemistry, whole-rock geochemistry and Sr–Nd isotopic compositions from the Early Devonian ultrapotassic Gucheng pluton in the North China Craton, and discuss its petrogenesis. The Gucheng pluton is exposed in the northern part of the North China Craton and forms a composite intrusion, consisting of K-feldspar-bearing clinopyroxenite, clinopyroxene-bearing syenite and alkali-feldspar syenite. Mineral phases in these lithologies include clinopyroxene (Wo43–48En19–35Fs18–38), sanidine (An0Ab3–11Or89–97), and subordinate titanite, andradite and Na-feldspar. These rocks show homogeneous Sr but variable Nd isotopic compositions, and have relatively high zircon in situ oxygen isotopes (δ18O = 5.2–6.7). The Gucheng plutonic rocks formed through fractional crystallization and accumulation from ultrapotassic magmas, which were originated from partial melting of metasomatic vein systems in the subcontinental lithospher...
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The accretionary prism of the Hengchun Peninsula at the southernmost tip of the active Taiwan orogen has newly emerged due to the transition from a subduction zone to an arc‐continent collision zone. The mafic rocks within the Hengchun... more
The accretionary prism of the Hengchun Peninsula at the southernmost tip of the active Taiwan orogen has newly emerged due to the transition from a subduction zone to an arc‐continent collision zone. The mafic rocks within the Hengchun accretionary prism, whose provenance has long been controversial, are highly indicative of the mantle nature and tectonic evolution around the northern Manila Trench. Based on geochemical analyses, the accreted basalts are classified as normal and enriched mid‐ocean ridge basalts (N‐MORB and E‐MORB) and alkaline ocean island basalts. The N‐MORBs, which exhibit geochemical signatures indicative of virtually unmetasomatized depleted MORB mantle and yield zircon U‐Pb ages of 22.8 ± 0.3 and 24.2 ± 1.1 Ma, were off‐scraped from the subducted oceanic crust of the South China Sea (SCS). The alkaline ocean island basalts are considered fragments of subducted seamount due to their geochemical similarity with seamount basalts from the SCS. The Hf‐Nd isotopic co...
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Research Interests: Geology, Geochemistry, Geophysics, Peridotite, Partial Melting, and 3 moreOlivine, Lithosphere, and Massif
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Because petrological processes in oceanic and continental domains occur largely in response to tectonic activities, teaching an undergraduate petrology course in a tectonic context is an effective way to convey the dynamic nature of... more
Because petrological processes in oceanic and continental domains occur largely in response to tectonic activities, teaching an undergraduate petrology course in a tectonic context is an effective way to convey the dynamic nature of crustal processes. Team-teaching the course allows each instructor to present material relevant to his or her area of research interests and to involve students in various aspects of ongoing research projects of the faculty. We try to teach students how to synthesize data and observations by combining traditional petrographic and hand-sample analysis with modern quantitative techniques of petrology (including computer modeling and graphical analysis) and to make interpretations about the spatial and temporal variation of crustal processes in the context of the evolution of characteristic petrotectonic environments.
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Abstract The Eldivan ophiolite along the Izmir–Ankara–Erzincan suture zone in north-central Anatolia represents a remnant of the Neotethyan oceanic lithosphere. Its upper mantle peridotites include three lithologically and compositionally... more
Abstract The Eldivan ophiolite along the Izmir–Ankara–Erzincan suture zone in north-central Anatolia represents a remnant of the Neotethyan oceanic lithosphere. Its upper mantle peridotites include three lithologically and compositionally distinct units: clinopyroxene (cpx)–harzburgite and lherzolite (Group-1), depleted harzburgite (Group-2), and dunite (Group-3). Relics of primary olivine and pyroxene occur in the less refractory harzburgites, and fresh chromian spinel (Cr-spinel) is ubiquitous in all peridotites. The Eldivan peridotites reflect a petrogenetic history evolving from relatively fertile (lherzolite and cpx–harzburgite) toward more depleted (dunite) compositions through time, as indicated by (i) a progressive decrease in the modal cpx distribution, (ii) a progressive increase in the Cr#s [Cr / (Cr + Al)] of Cr-spinel (0.15–0.78), and (iii) an increased depletion in the whole-rock abundances of some magmaphile major oxides (Al2O3, CaO, SiO2 and TiO2) and incompatible trace elements (Zn, Sc, V and Y). The primitive mantle-normalized REE patterns of the Group-1 and some of the Group-2 peridotites display LREE depletions. Higher YbN and lower SmN/YbN ratios of these rocks are compatible with their formation after relatively low degrees (9–25%) of open-system dynamic melting (OSDM) of a Depleted Mid-ocean ridge Mantle (DMM) source, which was then fluxed with small volumes of oceanic mantle-derived melt [fluxing ratio (β): 0.7–1.2%]. Accessory Cr-spinel compositions (Cr# = 015–0.53) of these rocks are consistent with their origin as residual peridotites beneath a mid-ocean ridge axis. Part of the Group-2 harzburgites exhibit lower YbN and higher SmN/YbN ratios, LREE-enriched REE patterns, and higher Cr-spinel Cr#s ranging between 0.54 and 0.61. Trace element compositions of these peridotites can be modeled by approximately 15% OSDM of a previously 17% depleted DMM, which was then fluxed (β: 0.4%) with subduction-influenced melt. The Group-3 dunite samples contain Cr-spinel with elevated Cr#s (0.73–0.78) and low-TiO2 contents (
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In this study we report on the petrography, major and trace element and mineral chemistry, platinum-group elements and Re-Os isotope systematics of depleted ultramafic rock suites from the Itmurundy Block in the North Balkhash ophiolite... more
In this study we report on the petrography, major and trace element and mineral chemistry, platinum-group elements and Re-Os isotope systematics of depleted ultramafic rock suites from the Itmurundy Block in the North Balkhash ophiolite zone in Kazakhstan. Represented mainly by variably serpentinized harzburgites and dunites, our samples are characterized by low whole-rock Al 2 O 3 (0.33-0.86 wt%), CaO (0.51-0.86 wt%) and Na 2 O (0.07-0.25 wt%) concentrations, and high-Mg olivine (Fo = 91-92) and orthopyroxene (Mg# = 92-93) contents, together with moderately high spinel Cr-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. 187 Os/ 188 Os values vary from 0.1202 to 0.12599, and 187 Re/ 188 Os ratios from 0.230 to 0.316. The Re-Os model ages (T MA) and maximum Re depletion model age (T RD) were calculated based on the obtained data. Re-Os isotope systematics suggests that the analysed peridotites formed in two stages: a first stage around 1.5 Ga and a later stage around 668-589 Ma.
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Constraining the timing of tectonic coupling between converging plates is crucial for un-derstanding the transition from continental subduction to continental collision. In the case of the India-Asia collision, thrusting of an... more
Constraining the timing of tectonic coupling between converging plates is crucial for un-derstanding the transition from continental subduction to continental collision. In the case of the India-Asia collision, thrusting of an accretionary complex onto the Indian continen-tal margin provides the most direct temporal constraint on the early stages of continental collision, as it represents the most immediate upper-crustal fault system corresponding to plate coupling. Here, we used structural analysis combined with K-Ar dating and hydrogen isotopes of authigenic illite and muscovite to unravel the time-progressive development of the Zhongba-Gyangze thrust (ZGT), which represents a tectonic boundary fault in southern Tibet. Our results suggest that the ZGT evolved from its initiation as a single fault zone infil-
trated by metamorphic fluids with high δD values (–47‰ to –55‰) at ca. 80 Ma to multiple deformation localization zones starting around 51 Ma. This latter phase is represented by
the development of different generations of authigenic 1 M/1Md illite and significant input
of meteoric fluids with δD values ranging from –71‰ to –98‰ through multiple episodes of brittle fault reactivation. A Late Cretaceous tectono-thermal event related to the subduc-tion of a Neotethyan oceanic ridge may have been responsible for the formation of 2M1 illite/muscovite at ca. 80 Ma. The oldest (ca. 51 Ma) 1 M/1Md illite age coincides with the first major pulse of shortening in the upper plate after the initial India-Asia contact. Given the synchronous deceleration of India-Asia convergence, the ca. 51 Ma deformation pulse across the Yarlung-Zangbo suture zone demarcates strong coupling (i.e., the onset of continental collision) between India and Asia at this time.
trated by metamorphic fluids with high δD values (–47‰ to –55‰) at ca. 80 Ma to multiple deformation localization zones starting around 51 Ma. This latter phase is represented by
the development of different generations of authigenic 1 M/1Md illite and significant input
of meteoric fluids with δD values ranging from –71‰ to –98‰ through multiple episodes of brittle fault reactivation. A Late Cretaceous tectono-thermal event related to the subduc-tion of a Neotethyan oceanic ridge may have been responsible for the formation of 2M1 illite/muscovite at ca. 80 Ma. The oldest (ca. 51 Ma) 1 M/1Md illite age coincides with the first major pulse of shortening in the upper plate after the initial India-Asia contact. Given the synchronous deceleration of India-Asia convergence, the ca. 51 Ma deformation pulse across the Yarlung-Zangbo suture zone demarcates strong coupling (i.e., the onset of continental collision) between India and Asia at this time.
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The Pozanti‐Karsanti ophiolite (PKO) in Turkey's eastern Tauride belt comprises mantle peridotites, ultramafic to mafic cumulates, isotropic gabbros, sheeted dikes and pillow lavas. The mantle peridotites are dominated by spinel... more
The Pozanti‐Karsanti ophiolite (PKO) in Turkey's eastern Tauride belt comprises mantle peridotites, ultramafic to mafic cumulates, isotropic gabbros, sheeted dikes and pillow lavas. The mantle peridotites are dominated by spinel harzburgites with minor dunites. The harzburgites and dunites have quite depleted mineral and whole‐rock chemical composition, suggesting high degrees of partial melting. Their PGEs vary from Pd‐depleted to distinct Pd‐enriched patterns, implying the crystallization of interstitial sulphides from sulphur‐saturated melts (e.g. MORB‐like forearc basalt). U‐shaped or spoon‐shaped REE patterns indicate that the PKO peridotites may have also been metasomatized by the LREE‐enriched fluids released from a subducting slab in a suprasubduction zone. Based on the mineral and whole‐rock chemical compositions, the PKO peridotites show affinities to forearc peridotites. Chromitites occur both in the mantle peridotites and the mantle‐crust transition zone horizon (MTZ...
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Various combinations of diamond, moissanite, zircon, corundum, rutile and titanitehave been recovered from the Bulqiza chromitites. More than 10 grains of diamond have been recovered, most of which are pale yellow to reddish–orange to... more
Various combinations of diamond, moissanite, zircon, corundum, rutile and titanitehave been recovered from the Bulqiza chromitites. More than 10 grains of diamond have been recovered, most of which are pale yellow to reddish–orange to colorless. The grains are all 100–300 μm in size and mostly anhedral, but with a range of morphologies including elongated, octahedral and subhedral varieties. Their identification was confirmed by a characteristic shift in the Raman spectra between 1325 cm−1 and 1333 cm−1, mostly at 1331.51 cm−1 or 1326.96 cm−1. This investigation extends the occurrence of diamond and moissanite to the Bulqiza chromitites in the Eastern Mirdita Ophiolite. Integration of the mineralogical, petrological and geochemical data of the Bulqiza chromitites suggests their multi–stage formation. Magnesiochromite grains and perhaps small bodies of chromitite formed at various depths in the upper mantle, and encapsulated the ultra–high pressure, highly reduced and crustal mineral...
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Research Interests: Geology, Geochemistry, Geophysics, Peridotite, Petrogenesis, and 3 moreOphiolite, Lithosphere, and Massif
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Mélanges occur widely in collisional and accretionary orogenic belts around the world and represent mappable geological units consisting of blocks of different ages and origin, commonly embedded in an argillitic, sandy, or serpentinite... more
Mélanges occur widely in collisional and accretionary orogenic belts around the world and represent mappable geological units consisting of blocks of different ages and origin, commonly embedded in an argillitic, sandy, or serpentinite matrix showing high stratal disruption and a chaotic internal structure. Understanding the mélange-forming processes and the significance of mélanges and related units in the geological record is of first-order significance in documenting the tectonic evolution of mountain belts; therefore, these chaotic rock units have attracted much attention in field-based structural studies since the nineteenth century. The term mélange has evolved to cover tectonic, sedimentary, and/or diapiric processes (Silver and Beutner, 1980) and tectonic settings of mélange formation, since its first use in 1919 by the British geologist Edward Greenly for the “Gwna Group” of the Mona Complex in Anglesey, north Wales (Greenly, 1919). In his classic work in the Franciscan Complex, Hsü (1968) proposed to use “mélange” only for tectonic mélanges and therein started a long-lived debate on the definition of the mélange term as well as on the processes involved in mélange formation. This controversy on the definition and formation of mélanges is livelier than ever in present time and requires a more systematic approach in mélange studies and better communication among the mélange researchers.
To this end, we organized and convened a topical session on mélanges during the Geological Society of America (GSA) Annual Meeting in Denver in 2007. The session was well attended by many international scientists from North America, Europe, and the Pacific Rim countries. This session was sponsored by the GSA International and the Structural Geology and Tectonics Divisions, and it brought together earth scientists in research communities from around the world, who do not ordinarily interact at the same meetings, in order to add an interdisciplinary dimension to our discussions on mélanges. It provided an excellent forum to discuss the new advances on the mélange concept as well as the diverse mélange types and mélange-forming processes based on some case studies. This Special Paper emanated from this successful GSA topical session. The benchmark GSA Special Paper 198 on mélanges, published more than 25 years ago (Raymond, 1984a), continues to influence research on mélanges, as testified by the fre-quent citation of the papers in it. The papers in the current volume build upon the solid foundation provided by the papers of Special Paper 198, as well as those published before and since, and include applications of new methodologies, exploration of new subjects, and a more international focus. The geographic spread of mélange localities around the world is also broader in parallel with the larger international authorship in the current volume.
Given the three-dimensional (3-D) complexity of mélanges, it is of little surprise that field studies form the foundation of all of the research presented in this volume. Beyond this common linkage, the papers here span a broad spectrum of features and focus. We streamlined the chapters according to a relative conceptual chronology related to mélange development (or impact) and related processes that begin with formation on the abyssal ocean floor (Part I), then proceed to subduction initiation (Part II), and accretionary wedge development and orogenic belt formation (Part III). The final section concentrates on the impact of mélanges on societies by way of their engineering properties (Part IV).
To this end, we organized and convened a topical session on mélanges during the Geological Society of America (GSA) Annual Meeting in Denver in 2007. The session was well attended by many international scientists from North America, Europe, and the Pacific Rim countries. This session was sponsored by the GSA International and the Structural Geology and Tectonics Divisions, and it brought together earth scientists in research communities from around the world, who do not ordinarily interact at the same meetings, in order to add an interdisciplinary dimension to our discussions on mélanges. It provided an excellent forum to discuss the new advances on the mélange concept as well as the diverse mélange types and mélange-forming processes based on some case studies. This Special Paper emanated from this successful GSA topical session. The benchmark GSA Special Paper 198 on mélanges, published more than 25 years ago (Raymond, 1984a), continues to influence research on mélanges, as testified by the fre-quent citation of the papers in it. The papers in the current volume build upon the solid foundation provided by the papers of Special Paper 198, as well as those published before and since, and include applications of new methodologies, exploration of new subjects, and a more international focus. The geographic spread of mélange localities around the world is also broader in parallel with the larger international authorship in the current volume.
Given the three-dimensional (3-D) complexity of mélanges, it is of little surprise that field studies form the foundation of all of the research presented in this volume. Beyond this common linkage, the papers here span a broad spectrum of features and focus. We streamlined the chapters according to a relative conceptual chronology related to mélange development (or impact) and related processes that begin with formation on the abyssal ocean floor (Part I), then proceed to subduction initiation (Part II), and accretionary wedge development and orogenic belt formation (Part III). The final section concentrates on the impact of mélanges on societies by way of their engineering properties (Part IV).
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The Mediterranean region and Asia provide an excellent natural laboratory in which to investigate the driving forces of conti-nental tectonics in an ongoing collisional orogen and the crustal and mantle response to various modes of... more
The Mediterranean region and Asia provide an excellent natural laboratory in which to investigate the driving forces of conti-nental tectonics in an ongoing collisional orogen and the crustal and mantle response to various modes of deformation associated with plate boundary processes. The multidisciplinary research efforts in this region through the collaborative work of the in-ternational earth science community over the last fifteen years have produced a wealth of new data and observations that allow us to better understand the interplay and feedback mechanisms between crustal and mantle processes and the dynamic land-scape evolution in a complexly deforming area. A number of discrete collisional events between the Gondwana-derived con-tinental fragments (i.e., Adria, Pelagonia, Arabia, and India) and Eurasia throughout the late Mesozoic and the Cenozoic con-trolled the geodynamic evolution of the Mediterranean region and Asia. The convergence between these continental blocks and the Eurasian mainland obliterated a series of interconnected Tethyan ocean basins, resulting in ophiolite emplacement, de-velopment of thickened orogenic crust, lateral escape of crustal fragments, and syn- to postcollisional magmatism. While the in-tervening ocean basins were closing during this collisional period, some new and rather small oceanic domains were cre-ated as a result of the opening of back-arc basins behind active subduction zones (i.e., the Tyrrhenian Sea, Aegean Sea, and Black Sea), lateral flow of mantle away from collision fronts, causing rapid opening of marginal basins along the strike of oro-genic belts (e.g., in the region of Indonesia) and/or slab rollback processes (e.g., in the Aegean and Tyrrhenian Seas). Magmatism associated with the opening of these embryonic basins produced within-plate alkaline volcanic and plutonic rock suites, mid-ocean ridge basalts, calc-alkaline island arc extrusives, and even new oceanic crust. Some of these most recently formed ocean basins are in the process of being closed, adding to the com-plexity of this collisional orogen stretching from the Alps to the Himalayas and Indochina. The short-term global positioning system (GPS) and long-term paleomagnetic evidence from dis-crete collision zones within the orogen have been particularly significant for our understanding of the recent geodynamics and active deformation in the Mediterranean region and Asia. Our findings from this natural laboratory have clearly been helping us to better understand the tectonic and magmatic processes in active collision zones, the mode and nature of continental growth, and the causes and distribution of seismic and volcanic events and their impact on humans and civilizations.
The papers on various aspects of the collision-induced tectonic, magmatic, and metamorphic events in the late Mesozoic–Cenozoic Mediterranean region in this book show that the traditional view of a single Alpine orogenic cycle explaining its tectonic evolution is no longer valid. The birth and demise of ocean basins and their paleogeographic extent throughout this time period are far more complicated than those widely accepted Tethyan models. The recent highly sophisticated, precise GPS data have shown us the magnitude and direction of plate motions and intraplate deformation, enabling us to better understand the crustal and mantle response to plate boundary processes. Thus, the compilation of papers involving many aspects of the collisional and postcollisional geology and geodynamics of the Mediterranean region and Asia in this volume should be of great interest to structural geologists, geochemists, petrologists, geophysicists, and geomorphologists working in this fascinating area and in other actively evolving collisional orogens. The papers here should stimulate future collaborative research efforts in the Mediterranean region and Asia that will in turn provide the information we need to better handle the natural hazards associated with active plate boundary processes and their impact on peoples and civilizations.
The papers on various aspects of the collision-induced tectonic, magmatic, and metamorphic events in the late Mesozoic–Cenozoic Mediterranean region in this book show that the traditional view of a single Alpine orogenic cycle explaining its tectonic evolution is no longer valid. The birth and demise of ocean basins and their paleogeographic extent throughout this time period are far more complicated than those widely accepted Tethyan models. The recent highly sophisticated, precise GPS data have shown us the magnitude and direction of plate motions and intraplate deformation, enabling us to better understand the crustal and mantle response to plate boundary processes. Thus, the compilation of papers involving many aspects of the collisional and postcollisional geology and geodynamics of the Mediterranean region and Asia in this volume should be of great interest to structural geologists, geochemists, petrologists, geophysicists, and geomorphologists working in this fascinating area and in other actively evolving collisional orogens. The papers here should stimulate future collaborative research efforts in the Mediterranean region and Asia that will in turn provide the information we need to better handle the natural hazards associated with active plate boundary processes and their impact on peoples and civilizations.