Geochronology and geochemistry of Late Cretaceous igneous intrusions and Mo-Cu-(W) mineralization in the southern Yidun Arc, SW China: Implications for metallogenesis and geodynamic setting

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• 作者：Xin-Song Wang^a ; ^b ; ^{gyigxsw@hotmail.com" class="auth_mail} ; Xian-Wu Bi^a ; ^{bixianwu@vip.gyig.ac.cn" class="auth_mail} ; Cheng-Biao Leng^a ; Hong Zhong^a ; Hong-Feng Tang^a ; You-Wei Chen^a ; Guang-Hou Yin^c ; Ding-Zhu Huang^c ; Mei-Fu Zhou^d
• 关键词：Zircon U&ndash ; Pb ; Molybdenite Re&ndash ; Os ; Porphyry Mo&ndash ; Cu deposits ; Meso-Tethys ; Yidun Arc ; Sanjiang
• 刊名：Ore Geology Reviews
• 出版年：September, 2014
• 年：2014
• 卷：61
• 期：Complete
• 页码：73-95
• 全文大小：3324 K

文摘

The Sanjiang Tethyan Metallogenic Domain (STMD) is an important part of the Tethyan giant metallogenic belt. The Yidun Arc is a part of the STMD in the eastern Tibetan Plateau. Recently, four newly discovered Mo-Cu-(W) ore deposits related to granitic intrusions were found distributed along the north-south strike in the southern Yidun Arc, which are identified as the Xiuwacu, Relin, Hongshan, and Tongchanggou deposits herein. These four deposits formed along high-angle north-northwest or north-west strike-slip faults, with vein-type and porphyry-type Mo-Cu mineralization developed in the intrusions. Molybdenite Re-Os and zircon U-Pb dating together with zircon Hf isotopes and whole-rock geochemistry of the intrusions were studied to discern the relationship between mineralization and magmatism, metallogenesis, and tectonic settings. Molybdenite from skarn-type mineralization at the Hongshan deposit has a Re-Os isochron age of 81.2 卤 2.6 Ma (MSWD = 1.3, n = 5) consistent with previously published zircon U-Pb ages and Re-Os ages of porphyry-type Mo mineralization. These results indicate that the Hongshan is a Late Cretaceous porphyry-skarn Cu-Mo deposit. Zircon U-Pb ages of the granitic intrusions in the Xiuwacu, Relin, and Tongchanggou deposits varying from ~ 87.4 Ma to ~ 82.7 Ma. Combined with published molybdenite Re-Os age spectrum (~ 85 Ma to ~ 81.2 Ma), it is proposed that the Mo-Cu-(W) mineralization in the Shangri-La region is spatially, temporally, and probably genetically related to the Late Cretaceous granitic intrusions. The Relin, Hongshan, and Tongchanggou intrusions have high SiO₂ (65.2-70.0 wt.%), Sr (363-905 ppm), Sr/Y (22-72), and La/Yb (37-69) ratios, and low Y (11.6-17.0 ppm) and Yb (0.97-1.59 ppm), which displayed adakitic affinities. Their low MgO (0.66-1.44 wt.%), Mg# (25-46), variable negative zircon 蔚_Hf(t) values (鈭?#xA0;7.9 to 鈭?#xA0;2.3), and Proterozoic two-stages Hf model ages (T_DM2 = 1.13-1.62 Ga) suggest that they were probably dominantly derived from partial melting of thickened lower continental crust. According to the tectonic evolution of the Bangong Meso-Tethys Ocean during the Late Mesozoic, the Late Cretaceous igneous event and mineralization in the Yidun Arc likely formed under a late- or post-collision extensional environment, probably related to the collision between the Lhasa and Qiangtang terranes during the Late Cretaceous.