青海祁漫塔格晚泥盆世侵入岩锆石U-Pb年龄、地球化学特征及其地质意义

U-Pb age of zircons of Qimantage late-Devonian intrusive rocks,geochemical characteristics and its geological significance,Qinghai

基于对青海1:5万喀雅克登塔格地区五幅区域地质调查项目的野外地质调查研究,综合其岩石学、时空分布和同位素年龄资料,确定了晚泥盆世的岩浆侵入事件,其岩性组合为暗色细粒闪长岩、肉红色细粒正长花岗岩、浅肉红色似斑状正长花岗岩等3类岩石组成。岩石系列属中—高钾钙性系列偏铝质—过铝质。暗色细粒闪长岩、肉红色细粒正长花岗岩、浅肉红色似斑状正长花岗岩3个侵入体中锆石的^(206)Pb/^(238)U年龄分别为(363±3)Ma、(370±3)Ma、(357±2)Ma,这些年龄数值被解释为岩体的侵位年龄。通过综合分析,认为祁漫塔格晚泥盆世侵入岩形成于早古生代造山后伸展崩塌的构造环境。

Based on the field geological investigation study from the regional mapping programme at the scale of 1：50,000 in the Kabul Jacques Tage area （5 map sheets） , in combination of the petrological, temporal and spatial distribution and isotope age data, the magma intrusion event occurred in the Late - Devonian period was identified, the magmatic rocks consist of the dark fine grain dio- rite, flesh red fine grain syenogranite and shallow flesh red porphyritic syenogranite. The intrusive rocks belongs to the a series of mod- erate- rich potassic and calcium, and aluminum and aluminum - saturated rock. The ages of 206pb/238U of zircon from these three types of intrusive are （363± 3） Ma, （370 ±3） Ma, （357 ± 2） Ma respectively, which are explained to the aging of the intrusive em- placement. Through the comprehensive analysis, it is concluded that the Qimantage intrusive rocks of Late - Devonian period were formed in the stretching tectonic environment of the early Paleozoie orogenic period.