内蒙古扎赉特旗辉长岩-闪长岩地球化学特征和LA-ICP-MS锆石U-Pb年龄  

Geochemical characteristics and zircon U-Pb age of the gabbro-diorite in Jalaid Banner of Inner Mongolia and their geological significance

作　　者：汪岩[1] 付俊彧[1] 那福超[1] 刘英才[1] 张广宇[1] 康庄[1] 杨帆[1] 

机构地区：[1]中国地质调查局沈阳地质调查中心.辽宁沈阳110034

出　　处：《地质通报》2013年第10期1525-1535,共11页Geological Bulletin of China

基　　金：中国地质调查局项目(编号:1212010781035、1212011220899)

摘　　要：扎赉特旗地区发育的辉长岩-闪长岩属钙碱性岩石系列。岩石相对富集LREE、大离子亲石元素(K、Rb、Ba和Sr)及U,亏损高场强元素(Th、Ta、Nb和Ti),类似于岛弧环境产物。推测其源区为岩石圈地幔,原生岩浆为幔源物质部分熔融产生,在上升过程中遭受微弱地壳混染。用LA-ICP-MS同位素测定方法,测得其中变辉绿岩、角闪辉长岩和辉长闪长岩的锆石206Pb/238U年龄平均值分别为317.3Ma±1.1Ma(30个数据点)、328.1Ma±1.3Ma(29个数据点)、325.2Ma±0.9Ma(32个数据点),为首次在扎赉特旗地区中基性岩体中获得较早的高精度岩体侵位年龄,指示扎赉特旗一带在早石炭世末期存在洋壳俯冲作用,为进一步研究二连浩特-贺根山碰撞拼合带东延至扎赉特旗一带的形成与演化提供了新的证据。The gabbro-diorite in Jalaid Banner of Inner Mongolia shows typical calc-alkalic rock series. The rocks are enriched in LKEE, LILE （K, P,b, Ba, Sr）, and U, and depleted in HFSE （Th, Ta, Nb, Ti）, implying products of island-arc structure setting. The authors hold that the gabbro-diorite magma originated from lithospheric mantle, and the primary magma resulted from partial melting of mande materials, with the mixture of small amounts of crust materials during the upward migration of the melt. LA-ICP-MS zir- con dating shows that the formation age of the diabase, gabbro and diorite is 317.3Ma±1.1Ma （30 data points）, 328.1Ma±l.3Ma （29 data points） and 325.2Ma±0.9Ma（32 data points） respectively. These are high-precision emplacement ages of intermediate-basic rock bodies obtained for the first time in Jalaid Banner area, which indicate that the subduction of oceanic crust existed in Jalaid Banner area at the end of early Carboniferous. The resulted obtained by the authors provide new evidence for further studying the Erenhot- Hegenshan collision collage belt which extended eastward to Jalaid area and its formation and evolution process.

关 键 词：辉长岩-闪长岩 地球化学特征 LA-ICP-MS锆石U-Pb 地质意义 扎赉特旗 

分 类 号：P595[天文地球—地球化学] P597.3[天文地球—地质学]