16 results on '"Xuan-Xue Mo"'
Search Results
2. Continental Crustal Growth Processes Recorded in the Gangdese Batholith, Southern Tibet
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Di-Cheng Zhu, Qing Wang, Roberto F. Weinberg, Peter A. Cawood, Zhidan Zhao, Zeng-Qian Hou, and Xuan-Xue Mo
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Space and Planetary Science ,Earth and Planetary Sciences (miscellaneous) ,Astronomy and Astrophysics - Abstract
The continental crust in the overriding plate of the India-Asia collision zone in southern Tibet is characterized by an overthickened layer of felsic composition with an underlying granulite-eclogite layer. A large data set indicates that this crust experienced magmatism from 245 to 10 Ma, as recorded by the Gangdese Batholith. Magmatism was punctuated by flare-ups at 185−170, 90−75, and 55−45 Ma caused by a combination of external and internal factors. The growth of this crust starts with a period dominated by fractional crystallization and the formation of voluminous (ultra)mafic arc cumulates in the lower crust during subduction, followed by their melting during late-subduction and collision, due to changes in convergence rate. This combined accumulation-melting process resulted in the vertical stratification and density sorting of the Gangdese crust. Comparisons with other similarly thickened collision zones suggests that this is a general process that leads to the stabilization of continental crust. ▪ The Gangdese Batholith records the time-integrated development of the world's thickest crust, reaching greater than 50 km at 55–45 Ma and greater than 70 km after 32 Ma. ▪ The Gangdese Batholith records three magmatic flare-ups in response to distinct drivers; the last one at 55−45 Ma marks the arrival of India. ▪ Magmatism was first dominated by fractional crystallization (accumulation) followed by crustal melting: the accumulation-melting process. ▪ Accumulation-melting in other collision zones provides a general process for vertical stratification and stabilization of continental crust.
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- 2023
3. Temporal and Spatial Variations of Enriched Source Components in Linzizong Volcanic Succession, Tibet, and Implications for the India–Asia Collision
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An-Lin Liu, Qing Wang, Di-Cheng Zhu, Peter A Cawood, Ying Xia, Shi-Min Li, Sheng-Ao Liu, Fang Huang, Li Liu, Zhi-Dan Zhao, and Xuan-Xue Mo
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Geophysics ,Geochemistry and Petrology - Abstract
The temporal and spatial distribution of enriched source components at sites of continent–continent collision provides critical insights into mantle dynamic processes associated with subduction- and collision-related events. However, determining the origin of such enriched components remains a significant challenge. We report a comprehensive dataset of the Linzizong volcanic succession (LVS) from four locations with varying distance across-strike to the Indus–Yarlung suture in southern Tibet, which marks the exposed surface expression of the India–Asia collision zone. The LVS rocks in this study can be divided into two groups: a calc-alkaline Group 1 (69–55 Ma), mainly including basaltic–andesitic varieties, and a shoshonitic Group 2 (52–50 Ma), consisting predominantly of silicic rocks with minor mafic compositions. Group 1 samples are likely derived from the fractional crystallization of primitive basaltic melts as a result of the partial melting of a metasomatized mantle wedge. These samples are decoupled in Nd–Hf isotopic compositions, suggesting an incorporation of subducting sediment-derived melts into the mantle wedge. The influence of sediment-derived melt on the mantle source increases away from the suture zone toward Asia (i.e., from the south to the north) as indicated by the more enriched Sr, Nd, Pb, and Hf isotopic compositions, as well as elevated Th/La and La/Sm ratios. The heavy δ26Mg values, and high Ba/Th and Sr/Th ratios of samples close to the suture coincide with the dehydration of the subducting Neo-Tethyan slab. Group 2 mafic samples have depleted and coupled εNd–εHf isotopic compositions and are characterized by elevated (La/Yb)N and Dy/Yb ratios as well as low Zr/Nb ratios, indicating an origin of enriched garnet-bearing lithospheric mantle with contributions from asthenosphere-derived materials. Group 2 silicic samples are isotopically enriched both near and far away from the suture, which can be attributed to the involvement of ancient lower crust-derived melt from Tethyan Himalaya and central Lhasa subterrane basement, respectively. Our results show that the LVS are the magmatic response to late subduction (Group 1), and to initial India–Asia collision and slab breakoff (Group 2). Negative trends in the whole-rock Nd and zircon Hf isotopic compositions at ~51 Ma should be treated with caution for geodynamic interpretations, depending on the distance between the samples and the India–Asia suture.
- Published
- 2021
4. Reconciling Orogenic Drivers for the Evolution of the Bangong‐Nujiang Tethys During Middle‐Late Jurassic
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Qing Wang, Shi Min Li, Roberto F. Weinberg, Peter A. Cawood, Xuan Xue Mo, Zhidan Zhao, Di-Cheng Zhu, and Robert J. Stern
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Paleontology ,Geophysics ,010504 meteorology & atmospheric sciences ,Geochemistry and Petrology ,010502 geochemistry & geophysics ,01 natural sciences ,Geology ,0105 earth and related environmental sciences - Published
- 2020
5. Raising the Gangdese Mountains in southern Tibet
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Qing Wang, Zhidan Zhao, Xuan Xue Mo, Di-Cheng Zhu, Peter A. Cawood, University of St Andrews. Earth and Environmental Sciences, University of St Andrews. School of Geography and Geosciences, University of St Andrews. Scottish Oceans Institute, and University of St Andrews. St Andrews Isotope Geochemistry
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Gangdese Batholith ,Research program ,GE ,010504 meteorology & atmospheric sciences ,NDAS ,Southern Tibet ,Paleoelevation ,010502 geochemistry & geophysics ,01 natural sciences ,Chinese academy of sciences ,Mineral resource classification ,China Geological Survey ,Crustal thickness ,Geophysics ,Economy ,Space and Planetary Science ,Geochemistry and Petrology ,Driving mechanism of uplift ,Earth and Planetary Sciences (miscellaneous) ,China ,Geology ,Seismology ,GE Environmental Sciences ,0105 earth and related environmental sciences - Abstract
This research was financially supported by the MOST of China (No. 2016YFC0600304 and No. 2016YFC0600407), the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (XDB03010301), the National Science Foundation of China (41225006 and 41472061), and the MOST Special Fund from the State Key Laboratory of Geological Processes and Mineral Resources (China University of Geosciences). The surface uplift of mountain belts is in large part controlled by the effects of crustal thickening and mantle dynamic processes (e.g., lithospheric delamination or slab breakoff). Understanding the history and driving mechanism of uplift of the southern Tibetan Plateau requires accurate knowledge on crustal thickening over time. Here we determine spatial and temporal variations in crustal thickness using whole-rock La/Yb ratios of intermediate intrusive rocks from the Gangdese arc. Our results show that the crust was likely of normal thickness prior to ca. 70 Ma (~37 km) but began to thicken locally at ca. 70 − 60 Ma. The crust reached (58 − 50) ± 10 km at 55 − 45 Ma extending over 400 km along the strike of the arc. This thickening was likely due to magmatic underplating as a consequence of rollback and then breakoff of the subducting Neo-Tethyan slab. The crust attained a thickness of 68 ± 12 km at ca. 20 − 10 Ma, as a consequence of underthrusting of India and associated thrust faulting. The Gangdese Mountains in southern Tibet broadly attained an elevation of >4000 m at ca. 55 − 45 Ma as a result of isostatic surface uplift driven by crustal thickening and slab breakoff, and reached their present-day elevation by 20 − 10 Ma. Our paleoelevation estimates are consistent not only with the C − O isotope-based paleoaltimetry but also with the carbonate clumped isotope paleothermometer, exemplifying the promise of reconstructing paleoelevation in time and space for ancient orogens through a combination of magmatic composition and Airy isostatic compensation. Publisher PDF
- Published
- 2017
6. Potassic magma genesis and the Ailao Shan-Red River fault
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Fu-tian Liu, Jinfu Deng, Cung Thu’ọ’ng Chí, Xuan-xue Mo, Chinh-hua Lo, Nguyễn Quốc Cu’ò’ng, Nguyen Van Hoang, and Martin F. J. Flower
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Geophysics ,Mantle wedge ,Subduction ,Asthenosphere ,Continental crust ,Earth science ,Geochemistry ,Flood basalt ,Crust ,Mantle (geology) ,Geology ,Seafloor spreading ,Earth-Surface Processes - Abstract
Two types of K-rich magma of Eocene to Early Oligocene (ca. 40–30) and Plio-Pleistocene (ca. 5–0.1 Ma) age were emplaced prior to and following left-lateral slip on the Ailao Shan-Red River (ASRR) fault, a regional shear zone extending between southwest China and the Tonkin Gulf (South China Sea) that accommodated ‘escape’ of the Indochina block. The first type is exposed in the Dali-Lijiang and adjacent regions of western Yunnan and Sichuan and comprises ultramafic potassic to ultrapotassic ‘absarokites’ and their shoshonite, banakite, and SiO 2 -rich derivatives which were emplaced immediately prior to activation of the ASRR fault. They are characterized by high Mg.-nos, and low contents of fusible oxides (FeO*, CaO, Al 2 O 3 ), for equivalent MgO content, and pronounced primitive mantle-normalized high-field strength element (HFSE) depletions. In contrast, ‘post-escape’ K-rich magmas were erupted in the Puer, Maguan-Pingbian regions of south and southeast Yunnan. Apart from their relative enrichments in potassium they show typical HFSE-rich intra-plate compositional affinity. Geological and geomorphic evidence, and thermochronologic age dating of metamorphisc events, suggest that left-lateral shearing occurred between ca. 30 and 17 Ma; thereby accommodating the southeastward ‘escape’ of Indochina and (possibly) two episodes of spreading in the South China Sea. The southwestern part of Dali-Lijiang magmatic products was detached and offset by ca. 600 km and are now located in Phan Xi Pang in northern Viet Nam. The same is true for the Permo-Triassic Emeishan flood basalts, whose western exposures were likewise displaced by the same amount and are now represented by the Song Da complex, also in northern Viet Nam. Here, we report geochemical, isotopic, and 40 Ar/ 39 Ar age data for samples from both the ‘pre-escape’ Dali-Lijiang magmas and the ‘post-escape’ K-rich Puer, Maguan-Pingbian basalts and basanites, with a view to comparing and contrasting their interpolated source compositions, estimated conditions of upper mantle melt segregation and, by inference, their mantle dynamic and contamination histories insofar as these were conditioned by the India-Asia collision. Our interpretations yielded two complementary conclusions. The first contends that the pre-escape magmas result from adiabatic melting of crust-contaminated asthenosphere comprising a ‘melange’ of continental lithospheric mantle (CLM) (hydrated by sab-derived hysdrous fluids released at 0.2–0.5 GPa) and lower crust, delaminated from the overriding plate during mantle wedge corner flow and further enriched by metasomatic melts of subducted continental crust. We postulate that incipient H 2 O-saturated melting of the ‘melange’ occurs at depths of between ca. 100 and 200 km after being ‘dragged’ down by relict oceanic slab fragments, in response to the dehydration of supra-subduction amphibole- and phlogopite. The ensuing viscosity ‘crisis’ and buoyancy relative to ambient ‘fertile’ convecting mantle of such asthenospheric ‘pockets’, and the collision-related change from lithospheric compression to extension, almost certainly predisposes such a refractory yet crust-contaminated ‘pockets’ to rapid adiabatic melting. The second conclusion concerns the post-escape K-rich basalts and basanites and is based on the contention that decompression melting of thermally anomalous K-rich asthenospheric occurred in response to regional post-escape transtension, concomitant with the cessation Indochina escape and contiguous seafloor spreading. However, although these magmas share the HFSE-rich fertile source character of other, widely dispersed, post-escape Cenozoic basalts they more specifically resemble relatively rare examples of intra-plate, K-rich activity observed in northeast China, central Spain, and elsewhere in Asia and Europe, arguably (indirectly) reflecting mantle perturbations caused by major continental collisions.
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- 2013
7. The Carboniferous ophiolite in the middle of the Qiangtang terrane, Northern Tibet: SHRIMP U–Pb dating, geochemical and Sr–Nd–Hf isotopic characteristics
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Jun Wang, Kuo-Lung Wang, Qingguo Zhai, Li Su, Hao-Yang Lee, Suo Han Tang, Bor-ming Jahn, and Xuan Xue Mo
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Basalt ,Rift ,Gabbro ,Geochemistry and Petrology ,Carboniferous ,Geochemistry ,Geology ,Paleo-Tethys Ocean ,Ophiolite ,Terrane ,Zircon - Abstract
article i nfo Ophiolite plays a key role in identifying paleo-ocean and paleo-plate and rebuilding the evolutionary history of ancient orogen. Mafic-ultramafic rocks are distributed in a broadly E-W direction in the middle of the Qiangtang terrane, northern Tibetan plateau. However, interpretation of these rocks as ophiolite and subsequent tectonic implications have been much disputed, and they were regarded by some to have an origin in a continental rift set- ting. A detailed zircon dating and geochemical and Sr-Nd-Hf isotopic study of this suite of rocks has been under- taken in order to clarify this important issue. The mafic-ultramafi cs uite was collected from the Gangma Co and Guoganjianian localities and is composed of cumulate and isotropic gabbro, basalt, actinolitite and plagiogranite. All basaltic rocks are tholeiitic and have low rare earth element (REE) abundances with variable REE patterns and slight negative Nb and Ti anomalies. These features are comparable with those of normal mid-ocean ridge ba- salts (N-MORB) and/or enriched mid-ocean ridge basalts (E-MORB). The positive whole-rock eNd(t) and zircon eHf (t) values indicate that these rocks were derivedfrom a long-term depleted mantle source. Zircon U-Pb dating using a sensitive high-resolution ion microprobe (SHRIMP) on two cumulate gabbros and two plagiogranites sam- ples yielded Carboniferous ages of 357±2.5 Ma, 356.1±3.0 Ma, 354.7±4.7 Ma and 345.4±4.6 Ma. The ophiolite marks a Paleo-Tethys Ocean basin in middle of the Qiangtang terrane, and it is interpreted as the western exten- sion of the Changning-Menglian Paleo-Tethys ophiolite in the eastern margin of the Tibetan plateau.
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- 2013
8. Triassic arc magmatism in the Qiangtang area, northern Tibet: Zircon U–Pb ages, geochemical and Sr–Nd–Hf isotopic characteristics, and tectonic implications
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Suo-han Tang, Kuo-Lung Wang, Jun Wang, Xuan Xue Mo, Li Su, Bor-ming Jahn, Qingguo Zhai, and Hao-Yang Lee
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Blueschist ,geography ,Felsic ,geography.geographical_feature_category ,Proterozoic ,Geochemistry ,Geology ,Anatexis ,Diorite ,Volcanic rock ,Oceanic crust ,Petrology ,Earth-Surface Processes ,Zircon - Abstract
Felsic magmatic rocks of Triassic ages occur on the north side of the Qiangtang metamorphic belt. Zircon dating using the SHRIMP and LA-ICP-MS techniques reveals that these rocks were emplaced between 223 and 205 Ma. The emplacement time is similar to the Ar–Ar ages of phengites and sodic amphiboles of the eclogites and blueschist from the Qiangtang metamorphic belt. The felsic magmatic rocks can be divided into two groups with distinct geochemical and Sr–Nd–Hf isotopic compositions. The first and older group (223–219 Ma) includes diorite from the Baohu area and some volcanic rocks from the Juhuashan area. These rocks have high Sr (291–1367 ppm) and low Y (5.5–13.9 ppm) contents with high Sr/Y ratios (28–117). They are characterized by slightly negative eNd(t) values (−1.9 to −5.7), positive eHf(t) values (+3.2 to +5.4) and young zircon Hf model ages (644–729 Ma). The second and younger group (215–210 Ma) comprises volcanic rocks from the Jiangai and Guoganjianian areas. They show high initial 87Sr/86Sr ratios (0.708–0.714), distinct negative eNd(t) (−9.6 to −7.9) and eHf(t) values (−15.3 to −10.1) and much older bulk-rock Nd model ages (1658–2178 Ma) and zircon Hf model ages (1251–2012 Ma). Geochemical arguments led us to suggest that the rocks of the first group were generated by the melting of subducted oceanic crust and associated sediments, and the second group rocks were derived from anatexis of the Proterozoic continent crust. In conclusion, the Late Triassic magmatic rocks from the northern Qiangtang have recorded the process from subduction to break-off of an oceanic slab. The Qiangtang metamorphic belt to the south represents a northward oceanic subduction zone.
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- 2013
9. Correction: Corrigendum: Magmatic record of India-Asia collision
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Fu-Yuan Wu, Peter A. Cawood, Yaoling Niu, Xuan Xue Mo, Sheng-Ao Liu, Sun-Lin Chung, Qing Wang, Di-Cheng Zhu, and Zhidan Zhao
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Multidisciplinary ,Computer science ,Collision zone ,Collision ,computer.software_genre ,Mantle (geology) ,Continental arc ,Paleontology ,Lithosphere ,Magmatism ,Slab ,Data mining ,Mafic ,computer - Abstract
New geochronological and geochemical data on magmatic activity from the India-Asia collision zone enables recognition of a distinct magmatic flare-up event that we ascribe to slab breakoff. This tie-point in the collisional record can be used to back-date to the time of initial impingement of the Indian continent with the Asian margin. Continental arc magmatism in southern Tibet during 80–40 Ma migrated from south to north and then back to south with significant mantle input at 70–43 Ma. A pronounced flare up in magmatic intensity (including ignimbrite and mafic rock) at ca. 52–51 Ma corresponds to a sudden decrease in the India-Asia convergence rate. Geological and geochemical data are consistent with mantle input controlled by slab rollback from ca. 70 Ma and slab breakoff at ca. 53 Ma. We propose that the slowdown of the Indian plate at ca. 51 Ma is largely the consequence of slab breakoff of the subducting Neo-Tethyan oceanic lithosphere, rather than the onset of the India-Asia collision as traditionally interpreted, implying that the initial India-Asia collision commenced earlier, likely at ca. 55 Ma.
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- 2015
10. [Raman active vibrations of aluminosilicates]
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Feng, Pan, Xue-hui, Yu, Xuan-xue, Mo, Jing-lin, You, Chen, Wang, Hui, Chen, and Guo-chang, Jiang
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Raman spectra of aluminosilicate minerals, namely kyanite, andalusite, and sillimanite and K2O-Al2O3-SiO2 glasses were recorded. Four alumino-silicon tetrahedral model clusters were calculated by self-consistent (SCF) molecular orbital ab-ini-tio calculation of the quantum chem (QC) method. The result shows a decrease tendency in Raman frequencies in the 800-1200 cm(-1) frequency region with increase in four-coordinated Al content, which is assigned to the Si--Onb symmetry stretching vibrations. The Raman spectra in the 700-800 cm(-1) frequency region is attributed to Al-Onb symmetry stretching vibrations.
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- 2007
11. THE GEOLOGY AND MINERALOGY OF THE BEIYA SKARN GOLD DEPOSIT IN YUNNAN, SOUTHWEST CHINA.
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WEN -YAN HE, XUAN-XUE MO, ZHONG-HUA HE, WHITE, NOEL C., JIN-BIAO CHEN, KAI-HUI YANG, RUI WANG, XUE-HUI YU, GUO-CHEN DONG, and XIONG-FEI HUANG
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GOLD ,MINERAL industries ,MINERALOGICAL research ,GEOLOGICAL research ,SKARN - Abstract
The Beiya skarn gold deposit is located in the eastern Tethyan orogenic belt in western Yunnan province, China. It is one of the largest gold deposits in China, with significant amounts of silver and base metals. To the end of 2014, the estimated resources are 125 million tonnes (Mt) of ore, grading 2.42 g/t Au, 0.48 wt % Cu, 25.5 wt % Fe, 38.85 g/t Ag, 1.24 wt % Pb, and 0.53 wt % Zn. Skarn alteration and mineralization are related to shoshonitic quartz monzonite porphyries that were emplaced in Triassic carbonates (Beiya Formation). Re-Os dating on molybdenite from a skarn orebody indicates an ore-forming age of 36.82 ± 0.48 Ma, which is consistent with previous dating results of the quartz monzonite porphyries. At least two paragenetic stages of skarn minerals and associated sulfides were recognized, with the early stage typified by garnet ± pyroxene, magnetite, and calcite, and the late stage characterized by epidote, amphibole, chlorite, quartz, and calcite, containing up to 70% sulfides (pyrite, chalcopyrite, and minor pyrrhotite). The early skarn is dominated by anhydrous minerals, which were replaced by hydrous minerals formed during the late stage. The garnet in the Beiya deposit is andradite rich (Ad
36-97 Gr3-61 ), and pyroxene is relatively diopside rich (Di8-91 Hd7-89 ). This mineral assemblage indicates an oxidized skarn system, similar to other Au-Cu, Fe-bearing skarn deposits around the world. Fluid inclusions from pyroxene indicate precipitation from high-temperature and high- to moderate-salinity fluids (420°-530°C, 11.1-43.3 wt % NaCl equiv), which probably results from boiling of a moderately saline magmatic fluid. Cooler (180°-365°C) and moderate- to low-salinity fluids (1.6-16.5 wt % NaCl equiv) were trapped in garnet and quartz and are interpreted to be responsible for gold deposition. Chlorite chemistry indicates ore-forming temperatures between 300° and 340°C, in agreement with fluid inclusion data. It appears that gold was transported as chloride complexes under oxidized conditions and was deposited at temperatures of about 300°C, when transport of chloride complexes as gold carriers was less efficient. [ABSTRACT FROM AUTHOR]- Published
- 2015
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12. Presence of Permian extension- and arc-type magmatism in southern Tibet: Paleogeographic implications.
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Di-Cheng Zhu, Xuan-Xue Mo, Zhi-Dan Zhao, Yaoling Niu, Li-Quan Wang, Qiu-Hong Chu, Gui-Tang Pan, Ji-Feng Xu, and Chang-Yong Zhou
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PERMIAN stratigraphic geology , *MAGMATISM , *PALEOGEOGRAPHY , *GEOLOGY - Abstract
The geographical location of the Lhasa terrane in the Permian remains a subject of debate. The recognition of the Permian basalts in the Tethyan Himalaya and the Permian volcanic rocks in the Lhasa terrane in southern Tibet together with the geochemistry of these rocks offer some new insights. The Permian basalts in the Tethyan Himalaya show a geochemical affinity with tholeiitic continental fl ood basalts, and are interpreted to have formed in an extensional setting. The new geochemical data and the geographical distribution of these basalts indicate that they probably represent the easternmost extent of the Panjal continental flood basalt province. All of the Permian basalts in the Lhasa terrane show a calcalkaline , high-alumina basalt affinity, with significant negative Nb-Ta-Ti anomalies. These geochemical features, combined with the recent documentation of the Permian Songdo eclogite and sedimentological observations, indicate the existence of a subduction system beneath the central Lhasa subterrane in the Permian. The presence of both extension- and arc-type magmatism of Permian age in present-day southern Tibet is inconsistent with the general view that the Lhasa terrane did not rift away from the northern margin of the Greater India until the Late Permian or Triassic. Instead, we suggest that the central Lhasa subterrane may have been a microcontinent isolated in the Paleo-Tethyan Ocean basin, at least during the Carboniferous--Middle Permian time. [ABSTRACT FROM AUTHOR]
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- 2010
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13. Early Cenozoic partial melting of meta-sedimentary rocks of the eastern Gangdese arc, southern Tibet, and its contribution to syn-collisional magmatism.
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Yuan-Yuan Jiang, Ze-Ming Zhang, Palin, Richard M., Hui-Xia Ding, and Xuan-Xue Mo
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CENOZOIC Era , *MELTING , *GEOCHEMISTRY , *PETROLOGY , *GEOLOGICAL time scales , *SEDIMENTARY rocks , *MAGMATISM - Abstract
Continental magmatic arcs are characterized by the accretion of voluminous mantle-derived magmatic rocks and the growth of juvenile crust. However, significant volumes of meta-sedimentary rocks occur in the middle and lower arc crust, and the contributions of these rocks to the evolution of arc crust remain unclear. In this paper, we conduct a systematic study of petrology, geochronology, and geochemistry of migmatitic paragneisses from the eastern Gangdese magmatic arc, southern Tibet. The results show that the paragneisses were derived from late Carboniferous greywacke, and underwent an early Cenozoic (69-41 Ma) upper amphibolite-facies metamorphism and partial melting at pressure-temperature conditions of ~11 kbar and ~740 °C, and generated granitic melts with enriched Hf isotopic compositions (anatectic zircon εHf(t) = -10.57 to +0.78). Combined with the existing results, we conclude that the widely distributed meta-sedimentary rocks in the eastern Gangdese arc deep crust have the same protolith ages of late Carboniferous, and record northwestward-decreasing metamorphic conditions. We consider that the deeply buried sedimentary rocks resulted in the compositional change of juvenile lower crust from mafic to felsic and the formation of syn-collisional S-type granitoids. The mixing of melts derived from mantle, juvenile lower crust, and ancient crustal materials resulted in the isotopic enrichment of the syn-collisional arc-type magmatic rocks of the Gangdese arc. We suggest that crustal shortening and underthrusting, and the accretion of mantle-derived magma during the Indo-Asian collision transported the supracrustal rocks to the deep crust of the Gangdese arc. [ABSTRACT FROM AUTHOR]
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- 2022
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14. The 132 Ma Comei-Bunbury large igneous province: Remnants identified in present-day southeastern Tibet and southwestern Australia.
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Di-Cheng Zhu, Sun-Lin Chung, Xuan-Xue Mo, Zhi-Dan Zhao, Yaoling Niu, Biao Song, and Yue-Heng Yang
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IGNEOUS rocks , *MANTLE plumes , *MAGMATISM , *GEMS & precious stones - Abstract
We report 11 new U-Pb zircon ages obtained by sensitive high-resolution ion microprobe (SHRIMP) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) for a large province of Early Cretaceous Comei igneous rocks consisting of basaltic lavas, mafi c sills and dikes, and gabbroic intrusions together with subordinate layered ultramafi c intrusions and silicic volcanic rocks exposed in the Tethyan Himalaya, southeastern Tibet. Available zircon U-Pb ages obtained from various rocks in this province, which has an areal extent of ∼40,000 km2 (∼270 km × 150 km), indicate that the magmatism occurred ca. 132 Ma ago, coeval with the Bunbury Basalt in southwestern Australia. Such a striking similarity in emplacement age, in combination with the tectonic reconstruction of eastern Gondwana ca. 132 Ma ago, allows us to propose that the extensive Comei igneous rocks in southeastern Tibet and the Bunbury Basalts in southwestern Australia may represent the erosional and/or deformational remnants of a large igneous province, which we call the Comei-Bunbury LIP. We argue that this newly identifi ed LIP was likely caused by the Kerguelen mantle plume, which started in the Early Cretaceous and may have played a role in the breakup of eastern Gondwana and the development of the 132 Ma old Weissert oceanic anoxic event. [ABSTRACT FROM AUTHOR]
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- 2009
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15. Northward subduction of Bangong-Nujiang Tethys: Insight from Late Jurassic intrusive rocks from Bangong Tso in western Tibet.
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Shi-Min Li, Di-Cheng Zhu, Qing Wang, Zhi-Dan Zhao, Qing-Lin Sui, Sheng-Ao Liu, Dong Liu, and Xuan-Xue Mo
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SUBDUCTION , *IGNEOUS intrusions , *TETHYS (Paleogeography) , *OLIVINE , *GEOCHEMISTRY - Abstract
New zircon LA-ICPMS U-Pb age data, whole-rock major and trace elements, and zircon Hf isotopic data of intrusive rocks from Larelaxin and Caima plutons in the southern margin of the Western Qiangtang subterrane provide important evidence of northward subduction of the Bangong-Nujiang Tethyan Ocean lithosphere. Host granitoids including quartz diorites, granodiorites, and syenogranites and associated mafic varieties including gabbroic enclaves, dioritic dikes and enclaves, and quartz dioritic enclaves are investigated in this study. Five host granitoid samples are dated at 163-160 Ma, and one dioritic dike and three dioritic enclave samples are dated at 162-158 Ma, which indicates that these rocks were contemporaneous. The quartz diorites and granodiorites are normal calc-alkaline I-type granitoids. The syenogranites are characterized by high SiO2 (74-77 wt.%) and differentiation index (DI = 92-97) and marked depletion in Ba, Nb, Ta, Sr, P, Ti, and Eu, thus indicating that they are highly fractionated I-type granitoids. The host granitoids exhibit uniform zircon εHf(t) values (- 1.4 to + 1.9). Considering the current data and their negative whole-rock εNd(t) values (- 4.7 to - 3.5) reported in recent studies, these rocks can be interpreted to have resulted from the partial melting of ancient mafic lower crust with varying contributions from mantle-derived or juvenile crust-derived components. One gabbroic enclave sample exhibits high Al2O3 (18.3 wt.%), low MgO (3.3 wt.%), high TiO2 (1.4 wt.%), and high Nb (24 ppm) and is geochemically similar to high-alumina basalt (HAB) and high-Nb basalt (HNB). This indicates that the gabbroic enclave originated from the partial melting of mantle wedge peridotite that was metasomatized by slab melting and subsequently experienced significant fractional crystallization of olivine and clinopyroxene. The dioritic dike and enclave samples yield εHf(t) values (- 1.6 to + 3.1) similar to those of the host granitoids. They most likely originated from magma mixing between mantle-derived and crust-derived melts at or close to the Moho. The intrusive rocks with geochemical diversity of the Larelaxin and Caima plutons from Bangong Tso in western Tibet can be interpreted to have resulted from melting, assimilation, storage, and homogenization (a MASH process) above subduction zones, thus indicating that the Bangong-Nujiang Tethyan Ocean lithosphere was subducted northward beneath the Western Qiangtang subterrane during the Late Jurassic. [ABSTRACT FROM AUTHOR]
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- 2014
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16. Lhasa terrane in southern Tibet came from Australia.
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Di-Cheng Zhu, Zhi-Dan Zhao, Yaoling Niu, Dilek, Yildirim, and Xuan-Xue Mo
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SEDIMENTARY rocks , *ZIRCON , *PALEOGEOGRAPHY , *PALEONTOLOGY , *PALEOZOIC stratigraphic geology , *INDUCTIVELY coupled plasma mass spectrometry - Abstract
The U-Pb age and Hf isotope data on detrital zircons from Paleozoic metasedimentary rocks in the Lhasa terrane (Tibet) define a distinctive age population of ca. 1170 Ma with εHf (t) values identical to the coeval detrital zircons from Western Australia, but those from the western Qiangtang and Tethyan Himalaya terranes define an age population of ca. 950 Ma with a similar εHf (t) range. The ca. 1170 Ma detrital zircons in the Lhasa terrane were most likely derived from the Albany-Fraser belt in southwest Australia, whereas the ca. 950 Ma detrital zircons from both the western Qiangtang and Tethyan Himalaya terranes might have been sourced from the High Himalaya to the south. Such detrital zircon connections enable us to propose that the Lhasa terrane is exotic to the Tibetan Plateau system, and should no longer be considered as part of the Qiangtang-Greater India-Tethyan Himalaya continental margin system in the Paleozoic reconstruction of the Indian plate, as current models show; rather, it should be placed at the northwestern margin of Australia. These results provide new constraints on the paleogeographic reconstruction and tectonic evolution of southern Tibet, and indicate that the Lhasa terrane evolved as part of the late Precambrian-early Paleozoic evolution as part of Australia in a different paleogeographical setting than that of the Qiangtang-Greater India-Tethyan Himalaya system. [ABSTRACT FROM AUTHOR]
- Published
- 2011
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