青海格尔木深沟地区基性侵入岩岩石地球化学特征及地质意义

Geochemical characteristics and geological significance ofbasic intrusive rocks in the Deep ditch area,Qinghai

青海省格尔木市深沟地区分布少量的基性侵入岩,岩性组合主要为辉长岩,并有少许辉石闪长岩、角闪岩等。基性侵入岩的锆石U-Pb年龄值分别为(205. 7±4. 5)Ma和(209. 1±3. 6) Ma,侵入岩属东昆仑地区印支晚期构造—岩浆活动的产物。主量元素地球化学成分上,基性侵入岩具有低Si、低K和高Fe、高Mg、高Ca的特征;稀土总量高且变化范围大,其"REE=70. 31×10^(-6)#309. 66×10^(-6)(平均193. 33×10^(-6))。绝大多数岩石的负铕异常明显(Eu/Eu*=0. 65#0. 75)。印支晚期基性侵入岩表现出Ba、K、P、Y元素的亏损和Zr、Hf元素的富集,说明岩体物质来源主要与富集型地幔有关。深沟地区基性侵入岩具有较好的形成铜镍硫化物矿床的条件。

There are a few of intrusive rocks distributed in Shengou district of Golmud,Qinghai. The majorlithology is gabbrowitha small amount of pyroxene diorite andamphibolite etc.. The zircon U-Pb ages of the basic intrusive rocks are( 205. 7 ± 4. 5) Ma and( 209.1±3.6) Ma respectively,the intrusive rocks are the product of the late Indosinian tectonic magmatic activities in the East Kunlun. About the major elements’ geochemical composition,the basic intrusive rocks is low in Si and K and is high in Fe,Mg and Ca;Thetotal amount of the rare earth( REE) is high and varies in a wide range of 70.31× 10-6~ 309.66 × 10-6( averageis of 193.33 ×10-6).The most majority of rocks hasnegative Eu anomalies( Eu/Eu*= 0.65 ~ 0.75). The basic intrusive rocks inlate Indosinian showthe lossof Ba,K,P and Y and enrichment of Zr and Hf,indicating that the source of rock mass is mainly related to the enriched mantle. Thebasic intrusive rocks in Shengou district have good conditions for the formation of copper-nickel sulfide deposits.