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Xing Yu - One of the best experts on this subject based on the ideXlab platform.
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hf isotopic characteristics of the tarim permian large igneous province rocks of nw china implication for the magmatic source and evolution
Journal of Asian Earth Sciences, 2012Co-Authors: Zilong Li, Yinqi Li, Shufeng Yang, Yigang Xu, Hanlin Chen, M Santosh, Charles H Langmuir, Zhongxing Chen, Xing YuAbstract:Abstract The Tarim large igneous province (TLIP) in northwestern China, covering an area of ca. 250,000 km2, includes large volumes of basalts, basic dyke swarms, mafic-ultramafic intrusion and minor picrite. Here we report systematic Hf isotope data from basalt, Diabase, olivine pyroxenite and syenitic porphyry from the TLIP and address the source components and magma evolution. The subdivision of the Tarim basalts shows that the Group 1 and Group 2 basalts are clearly differentiated based on different Nb/Y values, with two subgroups (Group 1a, Group 1b) identified based on distinct P2O5 vs. Mg# trends. The 176Hf/177Hf isotopic composition of the basalts ranges from 0.282584 to 0.282837. The eHf(t) of the basalts belonging to the Group 1a, Group 1b and Group 2 are −0.4–4.4, 0.5–2.1, and 1.9–3.1, respectively, and those of the intrusive suite of olivine pyroxenite, Diabase and syenitic porphyry show a range of 6.0–6.5, 4.5–5.7, and 6.5–8.3, respectively. The TLIP basalts generally show a good positive correlation between 176Hf/177Hf and 143Nd/144Nd, and fall in the field of the oceanic island basalts (OIBs) with low 176Hf/177Hf and 143Nd/144Nd, comparable to the basaltic lavas of the Pitcairn hotspot. These features, together with the enriched signature of the Tarim basalts might reflect the incorporation of partial melting of lithospheric mantle source in the early stages of the plume activity. The TLIP basalts show low eNd(t) and moderate eHf(t) OIB-like source. The 176Hf/177Hf-143Nd/144Nd values of the Group 1a and Group 1b basalts of the TLIP basalts are comparable to those from the Karoo high-Ti basalts, and those of the Group 2 basalts are comparable to the features of the Karoo low-Ti basalts and Diabases. The Group 1a and Group 1b basalts fall in the same Hf–Nd array, whereas the Group 2 basalts fall in a different array with much higher eNd(t). The olivine pyroxenite, Diabase and syenitic porphyry fall in the higher eNd(t) and eHf(t) field, with the olivine pyroxenite and Diabase having features close to OIB-like source. Our new Hf isotopic results suggest distinct sources for the Tarim basalts (285–290 Ma) and the intrusive rocks (274–284 Ma). Furthermore, the eHf(t) vs. eNd(t) plots show that the basalts and intrusive rocks might correspond to two different periods of magmatic activity in the Tarim Basin during the Early Permian, being comparable to the temporal evolution of different rock units in the TLIP. The eHf(t) and eNd(t) combined with other evidences address that the basalts could be explained by being derived from the asthenospheric (or plume) mantle and having interaction with lithospheric mantle source by mainly lower degree of partial melting in the early stage before the eruption, and should be much less proportion of crustal contamination during the period of 285–290 Ma, and the intrusive rocks might be derived from the primary magma and/or OIB-like mantle sources and underwent a magma process mainly by fractional crystallization and/or cumulation during the period of 274–284 Ma.
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temporal evolution of the permian large igneous province in tarim basin in northwestern china
Journal of Asian Earth Sciences, 2011Co-Authors: Zilong Li, Yinqi Li, Shufeng Yang, Biao Song, Hanlin Chen, Xing YuAbstract:Abstract The temporal relations of different types of rocks in the Tarim large igneous province (TLIP) are studied using stratigraphic correlation, lithologically spatial distribution and isotopic ages. The TLIP covers an area >250,000 km2 in the western and central part of the Tarim Basin. The lithological units of the TLIP include basalt, Diabase, layered intrusive rock, breccia pipe mica-olivine pyroxenite, olivine pyroxenite, gabbro, ultramafic dyke, quartz syenite, quartz syenite porphyry and bimodal dyke. This is the first report for the spatial distribution of the TLIP from the spatial section lines, which shows the stratigraphic correlation among basaltic lava, tuff, interlayered mudstone, siltstone and sandstone and the thicknesses of the basaltic lavas from different field sections and drill holes, and the basalts from the Kupukuziman and Kaipaizileike Formations were subdivided in the drill hole sections. This indicates that the basaltic lavas were widely distributed in the Tarim Basin. Combined with previous study of geochemical and Sr–Nd–Pb isotopic characterization from the basalts and their genetic link with mantle plume activity, and large Diabase swarms developments, the Permian igneous units constitute a Tarim large igneous province. Zircon SHRIMP U–Pb dating firstly yields 284.3 ± 2.8 Ma for the quartz syenite porphyry. Recent SHRIMP and LA-ICP-MS zircon U–Pb and 40Ar/39Ar ages are used to discuss temporal relations of different rock units in the TLIP formed between 290 and 274 Ma, and these data are more reliable than the K–Ar ages of 220–310 Ma reported previously. The sequence of magmatism of the TLIP in the central and western parts of the Tarim Basin are basaltic lava in the Kupukuziman and Kaipaizileike Formations (285–290 Ma), layered mafic–ultramafic rock, mica-olivine pyroxenite breccia pipe, Diabase and ultramafic dyke, quartz syenite, quartz syenite porphyry and bimodal dyke (274–284 Ma).
Hanting Zhong - One of the best experts on this subject based on the ideXlab platform.
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petrology and geochemistry of the xiugugabu ophiolitic massif western yarlung zangbo suture zone tibet
Lithos, 2011Co-Authors: Rachel Bezard, Rejean Hebert, Chengshan Wang, Jaroslav Dostal, Jingen Dai, Hanting ZhongAbstract:Abstract The Yarlung Zangbo Suture Zone (YZSZ), southern Tibet, is a discontinuous belt that is more than 2000 km long, composed of the remnants of Neo-Tethyan Mesozoic ocean. One of these relicts is the Xiugugabu ophiolitic massif which is a mantle thrust sheet of more than 260 km2 overlying the Cretaceous tectonic melange south of the YZSZ in SW Tibet. The massif is composed of harzburgites and clinopyroxene–harzburgites with porphyroclastic and porphyromylonitic textures. In the southern part of the massif, peridotites were intruded by amphibole-bearing microgabbro and microgabbronorite sills. A Diabase unit which is overlaid by a sedimentary sequence crops out on the NE flank of the massif. Mineral chemistry in harzburgites and clinopyroxene–harzburgites indicates compositions similar to abyssal and forearc peridotites. Peridotites are slightly LREE depleted to enriched with [La/Yb]CN 0.06–2.8 and [La/Sm]CN 0.34–2.64. These ultramafic rocks are inferred to be the residues of 5–25% of partial melting of a depleted mantle that has been enriched by percolating metasomatic melts in a suprasubduction environment. Amphibole–microgabbro and amphibole–microgabbronorite sills are mostly composed of brown to green amphibole, calcic plagioclase, clinopyroxene, ilmenite and orthopyroxene in gabbronorite. Textures and compositions of the brown amphiboles indicate a near-solidus high temperature hydrothermal origin (> 800 °C). These intrusive rocks are tholeiitic and show N-MORB type REE patterns ([La/Yb]NC 0.35–0.90), a LILE (mainly Th) enrichment and noticeable Nb, Ta and Ti negative anomalies. They have a suprasubduction affinity and were formed in a back-arc basin setting. The Diabase unit outcropping to the NE of the massif is not directly related to the ultramafic and mafic ophiolitic rocks. The Diabase shows LREE enriched patterns ([La/Yb]NC 8–8.9) and slight Nb, Ta and Ti negative anomalies. The Diabase has an intraplate affinity and could have been derived from a mantle source enriched by subduction-related fluids. The absence of continental crustal assimilation indicates that these rocks were probably emplaced in the Jurassic, in an oceanic environment after the Triassic disaggregation of the Indian plate. The data are consistent with the recent geodynamic model proposed for the central part of the suture for the closure of the Neo-Tethys and suggest that the geodynamic evolution of the western part of the basin was comparable to the central part.
Fuyuan Wu - One of the best experts on this subject based on the ideXlab platform.
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zircon u pb geochronological constraints on rapid exhumation of the mantle peridotite of the xigaze ophiolite southern tibet
Chemical Geology, 2016Co-Authors: Fuyuan Wu, Liangliang Zhang, Qingguo Zhai, Wenbin Ji, Chang Zhang, Yang XuAbstract:Abstract The Xigaze ophiolite outcrops in the central segment of the Yarlung Zangbo suture zone, southern Tibet. It is characterized by large amounts of ultramafic units with minor mafic rocks. The mafic rocks consist of gabbros, Diabases and basalts. The gabbroic rocks of the Xigaze ophiolite occur as layered bodies or isotropic dikes intruding into mantle sections. Hectometric-sized gabbroic bodies are well-preserved in Dazhuqu, Baigang and Jiding. However, their formation time and generation mechanism are not systematically proposed or well understood. In this study, nine samples of mafic rocks from the Xigaze ophiolite, including seven gabbros and two rodingites (altered from Diabases), were selected for in situ zircon U-Pb and Hf isotopic analyses. The geochemical feature suggested that these rocks formed by the intrusion of melts of normal mid-ocean ridge (N-MORB) type. The U-Pb data yielded identical ages of 124–129 Ma within uncertainties. Positive zircon eHf(t) values indicated that these samples had an origin of depleted mantle source. Combined with previous studies on mafic dikes, amphibolite blocks and radiolarian cherts, it can be concluded that the Yarlung Zangbo ophiolites formed over a short period of time from 119 to 132 Ma. Hence, a rapid exhumation of the mantle peridotites and gabbroic rocks of the Xigaze ophiolite may have occurred to get intrusion of the Diabase dikes and sills. It excludes the existence of a long-term ancient magma chamber or lens. It is more likely that the gabbroic rocks are a series of plutonic intrusions beneath a fossil slow-spreading ridge, rather than products of magma chambers. Therefore, the “Chapman detachment model” may be applied to the generation of the Yarlung Zangbo ophiolites.
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oceanic crust components in continental basalts from shuangliao northeast china derived from the mantle transition zone
Chemical Geology, 2012Co-Authors: Yigang Xu, Huihuang Zhang, Wenchun Ge, Fuyuan WuAbstract:Abstract Basaltic rocks from Shuangliao, northeast China include basanite, alkali olivine basalt, transitional basalt and sub-alkaline Diabase. Ar–Ar dating shows that the basanites and alkali olivine basalts formed earlier (48.5–51 Ma) than the transitional basalts and Diabases (43–41.6 Ma). These rocks have the highest Fe 2 O 3 contents (13.4–14.6 wt.%) and lowest ( 87 Sr/ 86 Sr) i ratios ( 206 Pb/ 204 Pb = 18.13–18.34) do not show the high time-integrated 238 U/ 204 Pb mantle component expected for a HIMU basalt. On a 206 Pb/ 204 Pb versus 207 Pb/ 204 Pb diagram, most samples straddle the Northern Hemisphere Reference Line (NHRL), in salient contrast to the majority of Chinese Cenozoic basalts, which plot above the NHRL. These data, as well as a comparison with high-pressure experimental melts, are consistent with the presence of young subducted oceanic crust (SOC) in the source of Shuangliao basalts. Varying ( 87 Sr/ 86 Sr) i , La/Nb and Eu/Eu* with rock-type suggests that the upper oceanic crust (with variable amount of lower oceanic crust) was preferentially sampled by earlier (51–48 Ma), highly alkaline rocks, whereas the lower oceanic crust was predominantly sampled in later (41–43 Ma) transitional basalts and Diabases. This temporal trend is attributed to the differential melting of a heterogeneous source in association with lithospheric thinning, during which fusible upper oceanic crust melted earlier than lower oceanic crust and peridotites. We postulate that the SOC components may have been derived from the seismically detected stagnant Pacific slab within the mantle transition zone. This hypothesis is supported by the same Indian MORB-like isotopic composition being found in the Shuangliao basalts and in the extinct Izanaghi–Pacific plate of NW Pacific. The latter has been subducting underneath the eastern Asian continent since the early Cretaceous.
Bin Xia - One of the best experts on this subject based on the ideXlab platform.
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origin of mesozoic ophiolitic melanges in the western yarlung zangbo suture zone sw tibet
Gondwana Research, 2019Co-Authors: Yun Zhong, Weiliang Liu, Gongjian Tang, Nina Liu, Hongfei Liu, Qinggao Zeng, Bin XiaAbstract:Abstract The petrogenesis and tectonic evolution of the Mesozoic ophiolitic melanges in the western section of the Yarlung Zangbo suture zone (YZSZ) remain controversial. In this paper, we present the results of whole-rock geochemical and Sr Nd isotope analyses, zircon U Pb ages and in situ Lu Hf isotopic data obtained from mafic rocks of the northern and southern sub-belts of the western YZSZ Mesozoic ophiolitic melanges to help us understand these controversial issues. Diabases and dolerites from the northern sub-belt and gabbros from the southern sub-belt exhibit variable fore-arc basalt (FAB)-like geochemical compositions and have zircon U Pb ages of ∼126.4–120.3 Ma. In addition, gabbro-Diabases from the northern sub-belt have boninite series affinities and yield a zircon U Pb age of ∼125.7 Ma. These results, along with previous studies on the YZSZ Mesozoic ophiolitic melanges and the Gangdese arc, reveal that the western YZSZ Mesozoic ophiolites were likely generated over multiple stages in the epicontinental Gangdese fore-arc basin as the Yarlung Zangbo Neo-Tethyan Ocean subducted northward in front of the Lhasa terrane. The Early Cretaceous FAB-like and boninite series mafic rocks were formed by the reinitiation of subduction, which was followed by a retreat of the subduction zone and the creation of the fore-arc basin and strong hyperextension, accompanied by asthenosphere upwelling at ∼130–120 Ma. During this process, the upwelling asthenosphere underwent decompressional melting with limited penetration of slab-derived fluids and gave rise to the N-MORB (normal mid-ocean ridge basalt)-like basaltic magmas that intruded the overlying, previously generated depleted mantle as FAB-like gabbro, Diabase and dolerite sills or dykes. Then, boninitic magmas represented by boninitic gabbro-Diabases were generated by remelting the extremely depleted residual mantle source, which was metasomatized by a small amount of slab-derived fluids, following previous extractions of FAB-like magma.
Zilong Li - One of the best experts on this subject based on the ideXlab platform.
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hf isotopic characteristics of the tarim permian large igneous province rocks of nw china implication for the magmatic source and evolution
Journal of Asian Earth Sciences, 2012Co-Authors: Zilong Li, Yinqi Li, Shufeng Yang, Yigang Xu, Hanlin Chen, M Santosh, Charles H Langmuir, Zhongxing Chen, Xing YuAbstract:Abstract The Tarim large igneous province (TLIP) in northwestern China, covering an area of ca. 250,000 km2, includes large volumes of basalts, basic dyke swarms, mafic-ultramafic intrusion and minor picrite. Here we report systematic Hf isotope data from basalt, Diabase, olivine pyroxenite and syenitic porphyry from the TLIP and address the source components and magma evolution. The subdivision of the Tarim basalts shows that the Group 1 and Group 2 basalts are clearly differentiated based on different Nb/Y values, with two subgroups (Group 1a, Group 1b) identified based on distinct P2O5 vs. Mg# trends. The 176Hf/177Hf isotopic composition of the basalts ranges from 0.282584 to 0.282837. The eHf(t) of the basalts belonging to the Group 1a, Group 1b and Group 2 are −0.4–4.4, 0.5–2.1, and 1.9–3.1, respectively, and those of the intrusive suite of olivine pyroxenite, Diabase and syenitic porphyry show a range of 6.0–6.5, 4.5–5.7, and 6.5–8.3, respectively. The TLIP basalts generally show a good positive correlation between 176Hf/177Hf and 143Nd/144Nd, and fall in the field of the oceanic island basalts (OIBs) with low 176Hf/177Hf and 143Nd/144Nd, comparable to the basaltic lavas of the Pitcairn hotspot. These features, together with the enriched signature of the Tarim basalts might reflect the incorporation of partial melting of lithospheric mantle source in the early stages of the plume activity. The TLIP basalts show low eNd(t) and moderate eHf(t) OIB-like source. The 176Hf/177Hf-143Nd/144Nd values of the Group 1a and Group 1b basalts of the TLIP basalts are comparable to those from the Karoo high-Ti basalts, and those of the Group 2 basalts are comparable to the features of the Karoo low-Ti basalts and Diabases. The Group 1a and Group 1b basalts fall in the same Hf–Nd array, whereas the Group 2 basalts fall in a different array with much higher eNd(t). The olivine pyroxenite, Diabase and syenitic porphyry fall in the higher eNd(t) and eHf(t) field, with the olivine pyroxenite and Diabase having features close to OIB-like source. Our new Hf isotopic results suggest distinct sources for the Tarim basalts (285–290 Ma) and the intrusive rocks (274–284 Ma). Furthermore, the eHf(t) vs. eNd(t) plots show that the basalts and intrusive rocks might correspond to two different periods of magmatic activity in the Tarim Basin during the Early Permian, being comparable to the temporal evolution of different rock units in the TLIP. The eHf(t) and eNd(t) combined with other evidences address that the basalts could be explained by being derived from the asthenospheric (or plume) mantle and having interaction with lithospheric mantle source by mainly lower degree of partial melting in the early stage before the eruption, and should be much less proportion of crustal contamination during the period of 285–290 Ma, and the intrusive rocks might be derived from the primary magma and/or OIB-like mantle sources and underwent a magma process mainly by fractional crystallization and/or cumulation during the period of 274–284 Ma.
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temporal evolution of the permian large igneous province in tarim basin in northwestern china
Journal of Asian Earth Sciences, 2011Co-Authors: Zilong Li, Yinqi Li, Shufeng Yang, Biao Song, Hanlin Chen, Xing YuAbstract:Abstract The temporal relations of different types of rocks in the Tarim large igneous province (TLIP) are studied using stratigraphic correlation, lithologically spatial distribution and isotopic ages. The TLIP covers an area >250,000 km2 in the western and central part of the Tarim Basin. The lithological units of the TLIP include basalt, Diabase, layered intrusive rock, breccia pipe mica-olivine pyroxenite, olivine pyroxenite, gabbro, ultramafic dyke, quartz syenite, quartz syenite porphyry and bimodal dyke. This is the first report for the spatial distribution of the TLIP from the spatial section lines, which shows the stratigraphic correlation among basaltic lava, tuff, interlayered mudstone, siltstone and sandstone and the thicknesses of the basaltic lavas from different field sections and drill holes, and the basalts from the Kupukuziman and Kaipaizileike Formations were subdivided in the drill hole sections. This indicates that the basaltic lavas were widely distributed in the Tarim Basin. Combined with previous study of geochemical and Sr–Nd–Pb isotopic characterization from the basalts and their genetic link with mantle plume activity, and large Diabase swarms developments, the Permian igneous units constitute a Tarim large igneous province. Zircon SHRIMP U–Pb dating firstly yields 284.3 ± 2.8 Ma for the quartz syenite porphyry. Recent SHRIMP and LA-ICP-MS zircon U–Pb and 40Ar/39Ar ages are used to discuss temporal relations of different rock units in the TLIP formed between 290 and 274 Ma, and these data are more reliable than the K–Ar ages of 220–310 Ma reported previously. The sequence of magmatism of the TLIP in the central and western parts of the Tarim Basin are basaltic lava in the Kupukuziman and Kaipaizileike Formations (285–290 Ma), layered mafic–ultramafic rock, mica-olivine pyroxenite breccia pipe, Diabase and ultramafic dyke, quartz syenite, quartz syenite porphyry and bimodal dyke (274–284 Ma).