新疆萨吾尔地区晚古生代岩浆作用的时限、地球化学特征及地球动力学背景

Time limit,geochemical characteristics and tectonic setting of late Paleozoic magmatism in Sawuer region,Xinjiang.

西准噶尔萨吾尔地区地处新疆阿勒秦地区吉木乃县及塔城地区和丰县。区内广泛发育晚古生代后碰撞岩浆岩,其中侵入岩年龄在328．2～290．7Ma之间,时代上属于晚石炭世至旱二叠世,哈尔加乌组、卡拉岗组火山岩年龄在296．7～280Ma之间,为早二叠世火山活动产物。区内侵入岩由早到晚(森塔斯岩体、沃肯萨拉岩体→塔斯特岩体→喀尔交岩体→阔依塔斯岩体、恰其海岩体)具有明显的地球化学演化特征。哈尔加乌组火山岩具有弱双峰式特征,卡拉岗组火山岩具有典型的双峰式特征,均形成于拉张的构造背景。基于萨吾尔地区晚古生代岩浆岩的时间框架、地球化学演化特征及其形成的地球动力学背景,我们认为晚石炭世至早二叠世,萨吾尔地区处于后碰撞构造背景,并逐渐由挤压-拉张过渡阶段演化到拉张阶段。

Sawuer region is located in west Junggar, Jimunai County of Altay district and Hefeng county of Tacheng district, Xinjiang province. The region is along the north margin of Kazakstan-Junggar plate. The post-collisional magma of late Paleozoic are widespread. The intrusions formed from 328. 2Ma to 290.7Ma （from late Carboniferous to early Permian ）, the volcanic rocks in Haerjiawu Group and Kalagang Group formed from 296. 7Ma to 280Ma （early Permian）. The geochemical evolvement characteristics of the intrusions from early to late （Sentasi intrusion, Wokensala intrusion→Tasite intrusion→Kaerjia intrusion→Kuoyitasi intrusion, Qiaqihai intrusion） are obviously. The volcanic rocks in Haerjiawu Group have weak bimodal characteristics and those in Kalagang Group have typical bimodal characteristics, indicating that they formed in extension setting. Based on the time frame, geochemical evolvement characteristics and tectonic setting of the late Paleozoic magma, we think that the Sawuer region was in post-collisional setting from late Carboniferous to early Permian, and the setting evolved from extrusion-extension translation stage to extension stage gradually.