摘要
本文对内蒙古双尖子山银多金属矿床花岗斑岩进行了锆石SHRIMP U-Pb定年,并对花岗斑岩的主量元素、微量元素组成进行了分析研究。结果显示,双尖子山花岗斑岩加权平均年龄为(133.4±1.2)Ma,为大兴安岭南段早白垩世岩浆活动集中期产物;花岗斑岩SiO_2含量为68.81%~70.05%,低MgO、TiO_2,K_2O/Na_2O为0.97~1.27,较为富钾;A/CNK在0.94~1.12之间,属准铝-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中等,δEu为0.55~0.62,Eu中等负异常。本文认为双尖子山银多金属矿床为多期次叠加的岩浆热液型矿床,160Ma和133Ma可能分别是岩浆活动的两个高峰期。花岗斑岩形成于陆内晚造山期-造山期后的伸展环境,蒙古-鄂霍次克洋俯冲板片在深部断离,引发软流圈物质上涌,这是导致大兴安岭南段早白垩世岩石圈伸展环境的主要机制。
This paper presents a series of studies on the granite porphyry from the Shuangjiauzishan silver polymetallic deposit, including dating of zir- con SHRIMP U - Pb, and analysis of major elements and trace elements. The results show that the granite porphyry, a product of active magmatic activity in the southern Dahinggan Mountains during the early Cretaceous, has an age of （ 133.4 _ 1.2） Ma on average. It contains 68.81% - 70.05% of SiO2 , and small amounts of MgO and TiO2. The K2O/Na2O value is between 0.97 to 1.27, indicating a feature of slight potassium - rich. The A/CNK is be- tween 0.94 and 1.12, which belongs to metaluminous -weak peraluminous series. The lithophylic elements （LILE） such as Rb, Th, U and K are rich, while HFSE such as Sr, P, and Ti are deficit. The total amount of race earth content EREE is normal. ~Eu is between 0.55 to 0.62. Eu is medium nega- tive anomalous. We conclude that the Shuangjianzishan silver polymetallic deposit belongs to the multi - period magmatic hydrothermal deposits. 160Ma and 133Ma are probably the two peak periods of magmatic activity, respectively. The granite porphyry formed under the condition of the intraplate environ- ment of late orogenic and post - orogenic extension. The resulted asthenospheric material upwelling due to the deep break of the subducting plate of Mon- golia - Okhotsk is the main mechanism of the intraplate extensional environment during the early Cretaceous in southern Dahinggan Mountains.
出处
《地质与勘探》
CAS
CSCD
北大核心
2017年第3期495-507,共13页
Geology and Exploration
基金
国土资源公益性行业科研专项(编号:201311018)资助
