The genetic relationship between the large Guanfang W deposit and granitic intrusions, in Yunnan Province, southwest China: Evidence from U-Pb and Re-Os geochronology and Pb and Sr isotopic characteristics

摘要

The recently discovered Guanfang large W deposit, in Yunnan Province, southwest China, is located in the Diandongnan thrust-nappe fold belt in the western part of the Cathaysia Block The orebodies occur at the contacts between the Suozuodi granite and Middle Cambrian marbles. LA-ICP-MS zircon U-Pb dating of the ore bearing Suozuodi granite yields a crystallization age of 91.6 +/- 1.0 Ma (MSWD = 0.56). An isochron age of 91.6 +/- 13 Ma (MSWD = 0.24) was obtained by Re-Os dationg of five molybdenite samples separated from sulfide-bearing ores. Scheelite at the Guanfang deposit is characterized by broad rangs of Pb isotopic ratios (Pb-207/Pb-204 = 15.568 to 15.735, Pb-206/Pb-204 = 17.912 to 18.390, Pb-208/Pb-204 = 38.491 to 38.730) and high initial Sr-87/Sr-86 ratios (Isr = 0.7118 to 0.7140), which consistent with the isotopic characteristics of the Suozuodi granite. Pb and Sr isotopic results indicate that the ore-forming materials were derived from a crustal source, without addition of mantle materials. The Guanfang tungsten deposit was formed in a syn-collision tectonic setting during the late stage of the Yanshanian tectonism. (C) 2016 Elsevier B.V. All rights reserved.