Early Cretaceous Granitoids Magmatism in the Nagqu Area, Northern Tibet: Constraints on the Timing of the Lhasa–Qiangtang Collision
The timing of the Lhasa–Qiangtang collision following the closure of the Bangong–Nujiang Tethys Ocean has not been well constrained. An integrated study of whole-rock geochemistry and zircon U–Pb–Hf isotopes was carried out for Early Cretaceous quartz diorite-porphyrites and granites from the Yilash...
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MDPI AG
2022-07-01
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| author | Kaiyang Wu Yun Zhong Yajuan Yuan Zhifeng Wan Bin Xia Tengfei Wu |
| author_facet | Kaiyang Wu Yun Zhong Yajuan Yuan Zhifeng Wan Bin Xia Tengfei Wu |
| author_sort | Kaiyang Wu |
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| description | The timing of the Lhasa–Qiangtang collision following the closure of the Bangong–Nujiang Tethys Ocean has not been well constrained. An integrated study of whole-rock geochemistry and zircon U–Pb–Hf isotopes was carried out for Early Cretaceous quartz diorite-porphyrites and granites from the Yilashan and Amdo areas, northern Tibet. LA–ICP–MS zircon U–Pb dating reveal that the Yilashan and Amdo granitoids were emplaced at ~121–110 Ma. These granitic rocks display selective enrichment of light rare earth elements, large ion lithophile elements (e.g., Rb, U) and Th, but depletion of Sr and high field strength elements (e.g., Nb, Ta, Ti) compared to its neighboring elements. These new data, combined with regional geological setting, show that these igneous rocks were formed under a geodynamic setting of the Lhasa and Qiangtang (–Amdo) collision with oceanic slab breakoff and asthenospheric upwelling. The BNTO had been closed at ~121–110 Ma in the study area. Yilashan-Amdo granitoids roughly yield high (<sup>87</sup>Sr/<sup>86</sup>Sr)<sub>i</sub> ratios and obvious negative ε<sub>Nd</sub>(t) and zircon ε<sub>Hf</sub>(t) values along with old Nd T<sub>DM</sub> and zircon Hf T<sub>DM2</sub> ages. Together with their variable U–Pb ages, these features indicate a Precambrian “hidden” crustal source beneath the northern Lhasa and Amdo terranes. The YLSS S-type granophyres were derived from partial melting of Paleoproterozoic lower crustal metagraywackes, whereas the YLSZ quartz diorite–porphyrites and the Amdo I- and A-type granites were mainly derived from partial melting of Paleo–Mesoproterozoic lower crustal mafic rocks with a certain amount of addition of mantle-derived melts. Minor amounts of the materials originated from the Amdo orthogneisses may also be involved in the formation of the YLSZ quartz diorite–porphyrites and the Amdo I-type granites. In addition, the Yilashan ophiolite was intruded by the ~112–108 Ma granophyric and quartz diorite–porphyritic intrusions before its final emplacement into the surrounding strata. |
| first_indexed | 2024-03-09T12:53:36Z |
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| spelling | doaj.art-1d33632134cf4907bb00424d13103e912023-11-30T22:02:45ZengMDPI AGMinerals2075-163X2022-07-0112893310.3390/min12080933Early Cretaceous Granitoids Magmatism in the Nagqu Area, Northern Tibet: Constraints on the Timing of the Lhasa–Qiangtang CollisionKaiyang Wu0Yun Zhong1Yajuan Yuan2Zhifeng Wan3Bin Xia4Tengfei Wu5School of Geography, South China Normal University, Guangzhou 510631, ChinaSchool of Surveying and Mapping, Guangdong Polytechnic of Industry and Commerce, Guangzhou 510510, ChinaSchool of Geography, South China Normal University, Guangzhou 510631, ChinaSchool of Marine Sciences, Sun Yat-sen University, Zhuhai 519082, ChinaSchool of Marine Sciences, Sun Yat-sen University, Zhuhai 519082, ChinaOklahoma Geological Survey, Norman, OK 73019, USAThe timing of the Lhasa–Qiangtang collision following the closure of the Bangong–Nujiang Tethys Ocean has not been well constrained. An integrated study of whole-rock geochemistry and zircon U–Pb–Hf isotopes was carried out for Early Cretaceous quartz diorite-porphyrites and granites from the Yilashan and Amdo areas, northern Tibet. LA–ICP–MS zircon U–Pb dating reveal that the Yilashan and Amdo granitoids were emplaced at ~121–110 Ma. These granitic rocks display selective enrichment of light rare earth elements, large ion lithophile elements (e.g., Rb, U) and Th, but depletion of Sr and high field strength elements (e.g., Nb, Ta, Ti) compared to its neighboring elements. These new data, combined with regional geological setting, show that these igneous rocks were formed under a geodynamic setting of the Lhasa and Qiangtang (–Amdo) collision with oceanic slab breakoff and asthenospheric upwelling. The BNTO had been closed at ~121–110 Ma in the study area. Yilashan-Amdo granitoids roughly yield high (<sup>87</sup>Sr/<sup>86</sup>Sr)<sub>i</sub> ratios and obvious negative ε<sub>Nd</sub>(t) and zircon ε<sub>Hf</sub>(t) values along with old Nd T<sub>DM</sub> and zircon Hf T<sub>DM2</sub> ages. Together with their variable U–Pb ages, these features indicate a Precambrian “hidden” crustal source beneath the northern Lhasa and Amdo terranes. The YLSS S-type granophyres were derived from partial melting of Paleoproterozoic lower crustal metagraywackes, whereas the YLSZ quartz diorite–porphyrites and the Amdo I- and A-type granites were mainly derived from partial melting of Paleo–Mesoproterozoic lower crustal mafic rocks with a certain amount of addition of mantle-derived melts. Minor amounts of the materials originated from the Amdo orthogneisses may also be involved in the formation of the YLSZ quartz diorite–porphyrites and the Amdo I-type granites. In addition, the Yilashan ophiolite was intruded by the ~112–108 Ma granophyric and quartz diorite–porphyritic intrusions before its final emplacement into the surrounding strata.https://www.mdpi.com/2075-163X/12/8/933granitoidgeochemistryzircon U–Pb datingcontinental–continental collisionBangong–Nujiang suture zone |
| spellingShingle | Kaiyang Wu Yun Zhong Yajuan Yuan Zhifeng Wan Bin Xia Tengfei Wu Early Cretaceous Granitoids Magmatism in the Nagqu Area, Northern Tibet: Constraints on the Timing of the Lhasa–Qiangtang Collision Minerals granitoid geochemistry zircon U–Pb dating continental–continental collision Bangong–Nujiang suture zone |
| title | Early Cretaceous Granitoids Magmatism in the Nagqu Area, Northern Tibet: Constraints on the Timing of the Lhasa–Qiangtang Collision |
| title_full | Early Cretaceous Granitoids Magmatism in the Nagqu Area, Northern Tibet: Constraints on the Timing of the Lhasa–Qiangtang Collision |
| title_fullStr | Early Cretaceous Granitoids Magmatism in the Nagqu Area, Northern Tibet: Constraints on the Timing of the Lhasa–Qiangtang Collision |
| title_full_unstemmed | Early Cretaceous Granitoids Magmatism in the Nagqu Area, Northern Tibet: Constraints on the Timing of the Lhasa–Qiangtang Collision |
| title_short | Early Cretaceous Granitoids Magmatism in the Nagqu Area, Northern Tibet: Constraints on the Timing of the Lhasa–Qiangtang Collision |
| title_sort | early cretaceous granitoids magmatism in the nagqu area northern tibet constraints on the timing of the lhasa qiangtang collision |
| topic | granitoid geochemistry zircon U–Pb dating continental–continental collision Bangong–Nujiang suture zone |
| url | https://www.mdpi.com/2075-163X/12/8/933 |
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