西准噶尔萨吾尔地区Ⅰ型花岗岩同位素精确定年及其意义  

Isotopic ages of the I type granitesin west Junggar Sawuer region.

作　　者：袁峰[1] 周涛发[1] 谭绿贵[1] 范裕[1] 杨文平 何立新 岳书仓[1] 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009 [2]新疆地质勘查局第四地质大队,阿勒泰836500

出　　处：《岩石学报》2006年第5期1238-1248,共11页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划项目(2001CB409800);安徽省优秀青年科技基金项目(04045063)资助.

摘　　要：西准噶尔萨吾尔地区地处新疆阿勒泰地区吉木乃县及塔城地区和丰县。区内酸性侵入岩较发育,森塔斯岩体中二长花岗岩锆石SHRIMP U-Pb年龄为328．2±5．7Ma(1σ),沃肯萨拉岩体中二长花岗岩锆石SHRIMP U-Pb年龄为323．8±6．2Ma(1σ),塔斯特岩体二长花岗岩全岩^(40)Ar/^(39)Ar年龄为313．6±3．2Ma(1σ),形成于早石炭世晚期。各岩体均具有Ⅰ型花岗岩特征,岩石偏碱性,Nd、Sr、Pb同位素显示出其幔源特征,具正常O同位素组成。森塔斯岩体、沃肯萨拉岩体和塔斯特岩体属于后碰撞花岗岩,其形成表明早石炭世晚期萨吾尔地区乃至西准噶尔地区已处于后碰撞构造环境,它们可能是后碰撞阶段挤压-伸展转变期的产物。森塔斯岩体、沃肯萨拉岩体和塔斯特岩体的岩石地球化学特征与准噶尔地区已知的Ⅰ型花岗岩(成岩年龄为300Ma左右)相似,但其发育显示准噶尔地区后碰撞Ⅰ型花岗岩的形成应始于早石炭世晚期。研究区早石炭世晚期后碰撞Ⅰ型花岗岩的确定为区域晚古生代地壳的垂向增生提供了新的证据。Sawuer region is located in west Junggar, Jimunai County of Altay district and Hefeng county of Tacheng district, Xinjiang. The region is along the north margin of Kazakstan-Junggar plate. The intrusions （ mainly acid） are widespread. The Sentasi intrusion, the Wokensala intrusion and the Tasite intrusion are mainly adamellite. According to SHRIMP U-Pb age analysis results, the crystallization age of Sentasi intrusion is 328.2±5.7Ma（1δ） and that of Wokensala intrusion is 323.8±6.2Ma（ 1δ）, and the age of Tasite intrusion is 313.6 ±3.2Ma（1δ） with ^40Ar/^39Ar age analysis results, corresponding to the afternoon of early Carboniferous. The intrusions belong to Ⅰ type granite and are the partial alkali rock. The Nd, St, Pb isotope compositions of the intrusions indicate a mantle source, while the δ^18O values are normal. The intrusions belong to post-collisional granite, indicating that the Sawuer region indeed west Junggar was in the post-collisional setting in the afternoon of early Carboniferous. They might form in the extrusion to extension period of the post-collisional stage. The geochemistry characteristics of the Sentasi, Wokensala and Tasite intrusions are similar to those of known Ⅰ type granites formed at about 300Ma in Junggar. The post-collisional Ⅰ type granites must begin to form in the afternoon of early Carboniferous in Junggar. The confirmation of post-collisional Ⅰ type granites of afternoon of early Carboniferous in the Sawuer region provides new evidence for the regional vertical continental growth in late Paleozoic.

关 键 词：花岗岩 锆石 SHRIMP年龄 ^40Ar/^30Ar测年 后碰撞 萨吾尔 新疆 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]