Origin of the Oligocene Tuolangla porphyry-skarn Cu-W-Mo deposit in Lhasa terrane,southern Tibet  

作　　者：Yong Huang Ming-hua Ren Wei Liang Guang-ming Li Kelly Heilbronn Zuo-wen Dai Yi-yun Wang Li Zhang 

机构地区：[1]Chengdu Center,China Geological Survey,Ministry of Natural Resources,Chengdu 610081,China [2]Department of Geoscience,University of Nevada,Las Vegas,NV 89154-4010,USA [3]Economic Geology Research Center,James Cook University,Townsville 4811,Australia [4]College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China

出　　处：《China Geology》2020年第3期369-384,共16页中国地质（英文）

摘　　要：Although some porphyry-skarn deposits occur in post-collisional extensional settings,the post-collisional deposits remain poorly understood.Here the authors describe the igneous geology,and mineralization history of Tuolangla,a newly-discovered porphyry-skarn Cu-W-Mo deposit in southern Tibet that belongs to the post-collisional class.The deposit is associated with Lower Cretaceous Bima Formation.It was intruded by granodiorite porphyry intrusions at about 23.1 Ma.Field investigation indicated that mineralization is spatially and temporally associated with granodiorite porphyry.Molybdenite yielded a Re-Os weighted mean age of 23.5±0.3 Ma and is considered to represent the age of skarn mineralization at the deposit.Theδ^34S values of sulfides,concentrated in a range between 0.6‰to 3.4‰,show that the sulfur has a homogeneous source with characteristics of magmatic sulfur.The Pb isotopic compositions of sulfides indicate that ore-forming metal materials were derived from the mantle and ancient crust.The granodiorite porphyry displays high SiO2(68.78%–69.75%)and K2O(3.40%–3.56%)contents,and relatively lower Cr(2.4×10^-6–4.09×10^-6),Ni(2.79×10^-6–3.58×10^-6)contents,and positiveεHf(t)values(7.7–12.9)indicating that the mineralization porphyry was derived from the partial melting of juvenile lower crust.The Tuolangla deposit is located in the central part of Zedang terrane.This terrane was once considered an ancient terrane.This terrane is in tectonic contact with Cretaceous ophiolitic rocks to its south and Mesozoic continental margin arc volcanics and intrusions of the Gangdese batholith of the Lhasa terrane to its north.Thus,the authors proposed that the Oligocene porphyry skarn Cu-W-Mo mineralization is probably associated with the Zedang terrane.This finding may clarify why the Oligocene(about 23 Ma)deposits are found only in the Zedang area and why mineralization types of the Oligocene mineralization are considerably different from those of the Miocene(17–14 Ma)mineralization.

关 键 词：Porphyry skarn type Cu-W-Mo deposit Geochronology Re-Os isotopic age Zircon U-Pb isotopic age Tuolangla Gangdese belt Tibet China 

分 类 号：P618.2[天文地球—矿床学]