内蒙古白音诺尔铅锌矿区三叠纪侵入岩体的发现及地质意义:锆石U-Pb年代学证据

白音诺尔铅锌矿位于大兴安岭南部晚古生代增生造山带,属大兴安岭南段主峰成矿亚带。矿区内,闪长玢岩呈脉状广泛出露,且同铅锌矿体空间关系密切。闪长玢岩通常作为矿床的成矿岩体,并沿用171Ma的成岩年龄。矿床属于与燕山期中酸性侵入岩有关的多金属成矿系列。该年龄值同矿区周围其他矿床成矿岩体的年龄(132.80～142.05 Ma)差别较大。利用锆石LA-ICP-MS U-Pb法对该矿区闪长玢岩和石英二长岩进行了测定,加权年龄分别为(242.3±3.6)Ma(MSWD=2.5,n=7)和(243.0±1.4)Ma(MSWD=1.4,n=12),均为三叠纪构造岩浆活动的产物。研究结果表明,该区在三叠纪处于造山后的伸展构造环境,深部岩浆上涌侵位,系列的构造岩浆活动伴随了以该矿床为例的少数三叠纪矿床的产出。

Discovery and Geological Significance of the Triassic Intrusive Rocks in the Baiyinnuoer Lead-Zinc Deposit,Inner Mongolia: Evidence from Zircon U-Pb Age

The Baiyinnuoer lead-zinc deposit is located in Late Paleozoic hyperplasia orogenic belt of the southern segment of Da Hinggan Mountains and belongs to main peak sub belts of mineralization.In mine area,diorite porphyrite is widely exposed as veins and spatially closely related to lead-zinc orebody.The previous researches regard it as metallogenetic rock,which intruded 171 Ma ago.The deposit belongs to multi metal metallogenic series,which is related to intermediate-acidic intrusive rocks of Yenshanian period.It has a big difference from those of deposits nearby.This paper has measured the diorite porphyrite and quartz monzonite with the method of LA-ICPMS U-Pb of zircons.The results are(242.3±3.6)Ma(MSWD=2.5,n=7) and(243.0±1.4)Ma(MSWD=1.4,n=12) that all are products of tectono-magmatic activities of Triassic.This area was in an postorogenic extensional tectonic environment at that time and following the deep magmatic intrusion.Then the deposit formed as a case of the minor Triassic deposits.