塔里木盆地二叠纪火成岩的同位素年代学

Isotopic geochronology of Permian igneous rocks in the Tarim Basin

在分区概述了塔里木盆地二叠纪火山—沉积地层的划分和对比的基础上，本文报道了2件玄武岩样品、2件辉长岩样品、1件辉绿岩样品、1件正长岩样品、1件英安斑岩样品和1件花岗闪长岩样品的锆石U-Pb法定年，表明强烈的火成活动发生在早二叠世（玄武岩定年294Ma，287Ma），可延续到中二叠世（辉长岩定年265Ma）。空间上，火山活动的中心位于巴楚—柯坪地区。玄武岩喷发可分为2个旋回，分别称南闸组和阿恰群中（火山岩）段；前者伴有英安斑岩（285Ma）喷发和辉长岩（283.1Ma）、辉绿岩（283Ma）侵入，正长岩（281.7Ma）则代表了区域上岩浆分异的晚期阶段。巴楚及邻近地区辉绿岩规律的北西走向指示了区域拉张应力场方向为北东—南西向。Ar-Ar法测年未获得理想的坪年龄值，仍支持了二叠纪早期发生过热事件的认识。

On a basis of classification and correlation of the Permian volcano-sedimentary strata in the Tarim Basin,the paper reported zircon U-Pb datings of 2 basalt samples,2 gabbro samples, 1 diabase,1 syenite,1 dacite porphyry and 1 granodiorite samples. The results showed that the violent igneous activity occurred in Early Permian（ the basalt datings 294 Ma and 287 Ma） , and it could continue till Middle Permian（the gabbro dating 265 Ma）. Specially, the center of the igneous activity situated in Baehu-Kalpin region. The basalt eruption could be divided into two cycles,recorded by the Early Permian Nanzha Formation and the Middle Permian Middle （Volcanic） Member of Aqal Group respectively. The basaltic eruption of the Nanzha Formation accompanied eruption of dacite porphyry （ 285 Ma） , intrusion of gabbro （ 283. 1 Ma） and diabase （283 Ma）,and the syenite（281.7 Ma）might present the late stage of magmatic differentiation in the area. The regular NW-striking of diabase in Bachu and adjacent areas indicated the regional tensile stress field being NE-SW orientation. Although the Ar-Ar dating couldn＇t get ideal plateau ages,it supported the knowledge that there was a thermal event in early period of Permian.