新疆西准噶尔恰其海后碰撞花岗岩

The Post-Collisional Granite in the Qiaqihai Area,Western Junggar,Xinjiang

恰其海地区地处新疆阿勒泰地区吉木乃县及塔城地区的丰县,其岩体位于哈萨克斯坦—准噶尔板块北缘。岩性主要为肉红色中粗粒黑云母钾长花岗岩,其次为黑云母花岗岩;其岩石地球化学判别为A2型花岗岩,即侵位于板块主碰撞后或后碰撞期的张性构造环境中。恰其海碱长花岗岩锆石SHRIMPU-Pb年龄测定的结果为(290.7±9.3)Ma(1σ),为早二叠世后碰撞岩浆活动的产物,显示恰其海区域就此进入后碰撞阶段伸展构造环境。

The Qiaqihai area is located in Jimunai County of Altay district and Hefeng County of Tacheng district, western Junggar of Xinjiang. The area is at the northern margin of Kazakstan-Junggar plate. The Qiaqihai intrusion is mainly pinkish red, middle-coarse grained biotite K-feldspar granite and secondly, biotite granite. They are classified as the A2-type granite based on geochemical discrimination, indicating a tectonic setting at the late period of the major collisional plate or at the extendable period of the post-collisional phase. The SHRIMP U - Pb zircon age for the Qiaqihai alkali-feldspar granite intrusion is （290.7±9.3） Ma （1σ）, representing the product of the post-collision magmatic activity during Early Permian. These show that Qiaqihai area has come into an extension setting of the post-collisional stage since then.