论文部分内容阅读
祁连南缘古生代超高压变质带 (榴辉岩年龄为 4 6 6～ 4 95 Ma)上一套中高级变质岩系 (达肯大坂片麻岩 )中存在三类花岗岩组合 : 类 :石英二长闪长岩 -花岗闪长岩 -二长花岗岩 , 类 :二长花岗岩 -二云母花岗岩-含白云母花岗岩 -正长花岗岩 , 类 :花岗闪长岩 -二长花岗岩 -黑云母花岗岩。 类岩石组合中的二长花岗岩锆石SHRIMP年龄为 4 73Ma, 类岩石组合中的正长花岗岩锆石 SHRIMP年龄为 4 4 6 Ma, 类岩石组合中的二长花岗岩锆石 SHRIMP年龄为 397Ma。从三类花岗岩组合的组成矿物来看 , 类和 类的矿物组合主要为斜长石、角闪石、石英、碱性长石、黑云母 , 类的矿物组合为钾长石、石英、白云母、黑云母、斜长石 ;从岩石地球化学特征上看 , 类和 类花岗岩为 型花岗岩 ,岩石的 Si O2 =6 1%～ 6 9% ,Na2 O/ K2 O>1,ANK<1,δEu=0 .7～ 1.0 ; 类花岗岩为 S型花岗岩 ,岩石的 Si O2 =70 %～ 76 % ,Na2 O/ K2 O<1,ANK>1,δEu=0 .1～ 0 .3;从构造环境上看 , 类花岗岩形成于岛弧环境或活动大陆边缘 , 类花岗岩形成于同碰撞 , 类花岗岩形成于碰撞后。结合区域地质特征 ,我们认为 ,早奥陶世 ,南祁连洋板块向北俯冲于祁连陆块之下 ,规模不大的南祁连洋很快闭合 ,但俯冲下去的大洋板块仍拖动柴达木陆块继续俯冲 ,俯冲?
There are three types of granite assemblages in a set of middle-high metamorphic rocks (Dakeng Osaka gneiss) in the Paleozoic ultrahigh-pressure metamorphic belt at the southern margin of the Qilian (eclogite age from 466 to 495 Ma): Class II: Long rock - granodiorite - monzonitic granite, type: monzogranite - two mica granite - muscovite granite - is a long granite, type: granodiorite - monzonite granite - biotite granite. The SHRIMP age of the monzonitic granite in the rock-like assemblage is 4 73Ma. The SHRIMP age of the orthoclase granite in the rock-like assemblage is 446 Ma, and the SHRIMP of the monzogranite in the rock-like assemblage is 397Ma. The mineral assemblages of clays and classes are mainly plagioclase, amphibole, quartz, alkaline feldspar and biotite from the mineral assemblages of the three types of granite assemblages. The mineral assemblages are K-feldspar, quartz and muscovite , Biotite and plagioclase. From the geochemical characteristics of the rocks, the class and granitic-type granites are characterized by Si O2 = 6 1% ~ 6 9%, Na 2 O / K 2 O> 1, ANK <1, δEu = 0 .7 ~ 1.0; type granites are S-type granites, rock Si O2 = 70% -76%, Na2 O / K2 O <1, ANK> 1, δEu = 0.1 ~ 0.3; From the point of view, granite-like rocks formed in the arc environment or active continental margin, granite-like granite formed at the same collision, granitoids formed after the collision. In combination with the regional geological features, we believe that the Early Ordovician and South Qilian ocean plate subducted northward beneath the Qilian block and the small-scale South Qilian Ocean closed quickly, but the subducted oceanic plate continued to drag the Qaidam block to continue Dive, dive?