新疆鄯善康古尔塔格蛇绿岩及其大地构造意义

Kangguertage ophiolite and tectornic significance,Shanshan,Xin iang China.

康古尔塔格蛇绿岩的岩石组合为变质橄榄岩-堆晶橄榄岩-辉长岩-斜长花岗岩-辉绿岩-玄武岩。方辉橄榄岩(蛇纹岩)、蛇纹石化辉石岩、蚀变辉长岩与特罗多斯蛇绿岩中同类型岩石类似,岩石总体低钾。变质橄榄岩 MgO/(MgO+TFeO)为0.834～0.866,TiO_2(wt%)为0.02%,为 SSZ 型蛇绿岩的变质橄榄岩。玄武岩的构造环境判别显示其形成于边缘海盆。放射虫硅质岩的 Al_2O_3/(Al_2O_3+Fe_2O_3)值平均为0.047,MnO/TiO_2比值平均为0.93,Ce 具负异常,Ce/Ce*=0.548,La_n/Ce_n=1.661,表明放射虫硅质岩的形成环境与洋中脊有密切关系。该蛇绿岩位于塔里木板块和哈萨克斯坦一准噶尔板块的艾比湖一康古尔塔格缝合线上,为一套无序产出的古生代北天山洋在该区的古洋壳残片。

The rock association of Kangguertage ophiolite includes metaperidotite-cumulus peridotite-gabbro-plagiogranite-diabasebasalt. The characters of harzburgite （ophite） , ophipyroxenite and erosive gabbro are similar to the type of Troodos. The low-K （for all rocks ）, MgO/（ MgO ＋ TFeO ） = 0. 834 - 0. 866 and TiO2 （ wt% ） = 0.02 % （ for metaperidotite） show the metaperidotite belongs to the type of SSZ ophiolite. In the light of tectonic discrimination diagrams of basalt, the SSZ ophiolite is formed in subduction plate margin of ocean basin. The average A1203/（Al2O3 ＋ Fe2O3 ） =0. 047, average MnO/TiO2 =0.93, Ce negative anomaly, Ce/Ce^ ＊ =0. 548 and Lan/Cen = 1. 661 （ all for radiolarian silicalite） , show that the formation of radiolarian silicalite bear affinitive relation on the ocean ridge or opened ocean. The ophiolite lies to the suture line of Talimu plate and Kazakhstan-Aibi Lake in Zhungeer plate-Kangguertage, which represents out-of-order formed relict fragments of ancient north Tianshan ocean lithosphere on late palaeozoic.