广西大厂锡矿田侵入岩SHRIMP锆石U-Pb年龄及其意义

SHRIMP Zircon U-Pb Dating of the Intrusive Rocks in the Dachang Tin—Polymetallic Ore Field, Guangxi and Their Geological Significance

应用高精度SHRIMP锆石U-Pb方法对广西大厂锡矿田不同类型中—酸性侵入岩进行了系统的定年研究,获得龙箱盖含斑黑云母花岗岩的成岩年龄为93±1Ma,斑状花岗岩91±1Ma,石英闪长玢岩脉(西岩墙)91±1Ma,花岗斑岩脉(东岩墙)91±1Ma,四者在测试误差范围内基本一致,微量元素特征及稀土配分模式相近,为同期不同阶段岩浆活动的产物。区内成岩与锡多金属成矿的时代相一致,均形成于板内伸展剪切的构造环境,应同属燕山晚期构造—热事件的产物。

The SHRIMP zircon U-Pb method was used to determine the ages of magmatites of the Dachang tin-polymetallic ore field. The Longxianggai biotite granite, which is the main part of the Longxianggai granite stock, was dated at 93±1 Ma （2σ, 8 spots, MSWD=1. 6）, porphyritic granite at 91±1 Ma （2σ, 10 spots, MSWD= 1.7）, granite-porphyry dyke （Eastern Dyke） at 91±1Ma （2σ, 12 spots, MSWD= 1.13） ,and quartz dioritic porphyrite （Western Dike） at 91±1 Ma （2σ, 8 spots, MSWD=1.11）. These data indicate that intrusive rocks in the Dachang tin district occurred in Middle Cretaceous, and that the mineralization and magmatic emplacement took place simultaneously and resulted from the same tectono-thermal event.