青海杂多县郭荣涌辉长岩的地质特征、精确测年和地质意义  

Geological Characteristics,U-Pb Zircon Dating and Geological Meaning of Gabbro in Guorongyong of Qinghai Zadoi County

作　　者：谈晓樱 马志远[2,3] 乔国栋[2,3] 欧阳光文[2,3] 王伟[2,3] 

机构地区：[1]青海省第一地质勘查院,青海平安810600 [2]青海省青藏高原北部地质过程与矿产资源重点实验室,青海西宁810012 [3]青海省地质调查院,青海西宁810012

出　　处：《甘肃冶金》2016年第4期55-58,63,共5页Gansu Metallurgy

基　　金：基金项目:青海然者涌-东莫扎抓地区矿产远景调查

摘　　要：青海杂多县郭荣涌一带出露的辉长岩岩体多为小的岩株状产出。其岩性从薄片鉴定来看为闪长岩,其岩石成分以斜长石和角闪石为主组成。而岩石化学显示SiO_2低于53%,为典型的基性岩类,岩石化学成分中Ti O_2、Fe O、Mg O、Ca O、Na_2O含量高,贫F_2O_3、MnO、K_2O和P_2O_5的特点,且K_2O<Na_2O。微量元素与洋壳及上地幔相比:Sc、Zr、Sr比较相近,Th、Hf、Ba略高。轻重稀土分馏不明显,铕异常不明显。分析其形成环境,是洋壳俯冲于下地幔重熔演化的产物。精确锆石U-Pb测年,反映其形成时间为244±3Ma,说明为早三叠世侵位。岩体处于北羌塘-昌都陆块的杂多晚古生代-中生代活动陆缘,在西金乌兰湖-金沙江构造缝合带南侧,从而说明了西金乌兰湖-金沙江构造缝合带是向南俯冲,且俯冲时间可能持续到早三叠世。The gabbro occurrence is small stock in Guo Rongyong of Qinghai Zadoi County.h belong to diorite by the slice determiinnation, primarily composed of the plagioclase feldspar and the amphibole.But the petrochemistry demonstration is the gabbroite, therein the contents of the TiO2 , FeO, MgO, CaO, and N% O are high, and that for F2 O3 , MnO, K2O and P2O5 are poor, also K2O〈Na2O.The results of trace element comparison with the ocean shell and the upper mantle are：Sc,Zr,Sr are quite close, Ba,Th, Hf are slightly high. LREE AND HREE fractionation is not obvious, Trace amount of elements comparison with oceanic crust and upper mantle：the high field strength elements Sc, Zr relatively similar, Th, Hf are slightly higher compared with low field strength elements, similar to Sr, and Ba is slightly higher.LREE fractionation is not obvious, Eu anomaly is not obvious. Through analysis of the formation environment, it is subducted oceanic crust in mantle melting under the product of evolution,. Accurate U-Pb zircon dating reflected the formation time of 244±3Ma,in the Early Triassic emplacement. The rock body is located in the heteropoly Changdu Late Paleozoic-Mesozoic active continental margin of the North Qiangtang-Changdu block, to the south of the suture zone for the Xijir Ulan Lake- Jinsha structure, suggesting south- ward subduction, and subduction duration is likely lasted to the early Triassic.

关 键 词：辉长岩 地质特征 U—Pb测年 西金乌兰湖-金沙江构造混杂带 

分 类 号：P588.124[天文地球—岩石学]