摘要
藏东玉龙超大型斑岩铜矿床是目前西藏发现的最大斑岩铜矿床,含铜岩体主要由早期石英二长斑岩及晚期正长花岗斑岩组成。本文用LA-ICP-MS法测定早期石英二长斑岩及晚期正长花岗斑岩锆石U-Pb年龄及Ar-Ar法测定钾质蚀变带黑云母的Ar-Ar年龄,发现玉龙含矿斑岩体早期石英二长斑岩锆石LA-ICP-MS U-Pb年龄(41.3±0.3Ma,MSWD=0.92)与晚期正长花岗斑岩锆石LA-ICP-MS U-Pb年龄(41.3±0.2Ma,MSWD=1.24)基本相同,也和黑云母Ar-Ar坪年龄(41.7±0.8Ma)及等时线年龄(41.3±0.8Ma)在误差范围内一致。玉龙斑岩铜矿早期及晚期岩体锆石U-Pb年龄一致表明含矿岩体在地质上的早期及晚期主要是岩浆在较短时间内脉动侵入所致。玉龙含矿岩体锆石U-pb年龄(封闭温度约800℃)、^(39)Ar-^(40)Ar年龄(封闭温度约300℃)及前人获得的Re-0s年龄40.1±1.8Ma(封闭温度约500℃)在误差范围内基本一致,表明含矿岩体岩体快速冷却,玉龙超大型斑岩铜矿床成岩成矿系统时间跨度小于1Ma。
The Yulong porphyry copper ore is the largest one found in collision zone in the eastern Tibet, China. The ore-bearing porphyry, which hosts 6. 5 Mt Cu with an outcrop area of 0. 64km^2 , consists mainly of early stage quartz monzonite porphyry and late stage syenite granite porphyry. The early stage quartz monzonite porphyry has zircon LA-ICP-MS U-Pb age of 41.3 ±0. 3Ma, with MSWD =0. 92 and the late stage syenite granite porphyry has zircon LA-ICP-MS U-Pb age of 41.3 ±0. 3Ma, with MSWD = 1.24. The zircon age of the Yulong ore-bearing porphyry is indistinguishable within error from an Ar-Ar plateau age 41.7 ±0. 8Ma and isochron age of 41.3 ±0. 8Ma for biotite from the potassic alteration zone and the reported Re-Os age for molybdenite mineralization （40. 1 ± 0. 8Ma） of the Yulong deposit. The concordance of the zircon U-Pb data of the early stage monzonite porphyry and the late stage syenite granite porphyry suggests that the Yulong porphyry emplaced essentially the same time. The agreement among zircon U-Pb, molybdenite Re-Os, and the biotite ^40At_^39 Ar ages in the Yulong porphyry indicates the Yulong ore-forming system cooled from about 800℃ （ zircon crystallization temperature） through 500℃（closure temperature for Re-Os in molybdenite） to below 300℃ （the closure temperature for Ar in biotite） in a very, short period. The duration of the Yulong giant ore-forming system is less than 1Ma.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2008年第10期2352-2358,共7页
Acta Petrologica Sinica
基金
国家自然科学基金项目(40772054
40472049)
西部矿业西藏资源投资公司项目资助
