内蒙古边家大院铅锌银矿床深部正长花岗岩年代学与形成环境研究

发布时间：2018-04-29 00:33

  本文选题：A型花岗岩 + 高温低压环境　； 参考：《中国地质》2017年01期

【摘要】：文章对内蒙古边家大院铅锌银多金属矿床深部正长花岗岩进行了LA-ICP-MS锆石U-Pb同位素测年,并对花岗岩的主量元素、微量元素和Sr-Nd同位素组成做了分析研究。结果显示,边家大院正长花岗岩加权平均年龄为(140.31±0.34)Ma,为大兴安岭南段早白垩世岩浆活动集中期产物;研究区至少有两期岩浆活动,早期酸性岩浆侵位,约10 Ma后中基性岩浆侵位,成岩与成矿同期进行。花岗岩地球化学特征具有高Si O2、K2O,低Mg O、Ca O、Ti O2的主量元素特征,A/CNK在0.98~1.19,属于准铝-弱过铝系列;富集Rb、Th、U、K等大离子亲石元素(LILE),亏损Sr、P、Ti等高场强元素(HFSE);稀土总量ΣREE较大,δEu为0.12~0.14,强烈Eu负异常;(87Sr/86Sr)i和(143Nd/144Nd)i初始比值,分别介于0.7066~0.7077和0.5121~0.5122(t=140 Ma),εNd(t)为-5.0‰~-6.6‰,成岩物质来自于中元古界下地壳铁镁质源岩的部分熔融。研究表明边家大院正长花岗岩是在早白垩世受到了蒙古—鄂霍次克海"剪刀式"闭合造山后的伸展条件和岩石圈减薄作用的影响,形成于高温低压环境的A型花岗岩。高温低压环境还可能与该区域岩石圈发生拆沉作用有关。
[Abstract]:In this paper, the LA-ICP-MS zircon U-Pb isotopic dating of the deep syenite in the Banjiayuan lead-zinc-silver polymetallic deposit, Inner Mongolia, has been carried out, and the main elements, trace elements and Sr-Nd isotopic compositions of the granite have been analyzed and studied. The results show that the weighted mean age of syenite is 140.31 卤0.34 Ma, which is the product of early Cretaceous magmatic activity in the southern part of Daxinganling, and there are at least two periods of magmatic activity in the study area, the early acidic magma emplacement, and the middle basic magma emplacement after about 10 Ma. Diagenesis and mineralization take place at the same time. The geochemical characteristics of granites are characterized by high Sio _ 2 K _ 2O and low mg _ 2O _ (Ca) O _ (2) O _ (2) O _ (2). It is rich in large ion lithophile elements, such as RbBX, Th, U, K, and depleted in high field strength elements, such as SRP Pu Ti, the total amount of rare earth 危 REE is larger, 未 EU is 0.12U 0.14, and the initial ratios of strong negative EU anomalies, such as 87Srrr / 86Srti and 143NdP / 144NdI, are between -5.0 鈥，

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