摘要
阿拉尔花岗岩体出露于阿尔泰造山带南缘可可托海地区喀依尔特-乌什托克斯一带,主要由斑状黑云钾长花岗岩、斑状黑云二长花岗岩(中心相),黑云钾长花岗岩、二云钾长花岗岩、二云二长花岗岩(过渡相)和黑云母花岗岩(边缘相)组成。对其进行了LA-ICP-MS锆石U-Pb年代学和岩石地球化学研究。结果显示,中心相的锆石206Pb/238 U年龄加权平均值为210±5Ma和218.7±3.3Ma,限定该岩体的形成时代为晚三叠世。岩石高硅(SiO2=65.33%~74.74%)、富钾(K2O=3.82%~6.02%,K2O/Na2O=1.27~2.32)、铝(Al2O3=12.87%~15.19%,A/CNK=0.85~1.17)、低钛(多小于0.33)和贫镁(MgO=0.16%~1.78%)、铁(Fe2O3T=1.79%~4.98%),为准铝质到弱过铝质的高钾-钾玄岩系列。稀土元素总量较高(123×10-6~363×10-6),轻稀土元素相对富集,有明显的负Eu异常(δEu=0.29~0.60)。微量元素Ba、Sr、Ti、Nb、Ta等具负异常,Rb、Th、Sm等具正异常,Rb/Sr比值较高(0.77~3.56,均值为1.57),显示S型花岗岩特征。结合区域资料,认为阿拉尔花岗岩形成于后碰撞造山向板内环境的转换阶段,是含泥质的变质杂砂岩地壳熔融的产物,且其可能与可可托海3号伟晶岩脉具有成因联系。
Aral granitic plutons extend from Kayierte to Wushituokesi in Koktokay area in the Southern Altaids.Lithological assemblage is composed principally of porphyritic biotite K-feldspar granite,porphyritic biotite adamellite(central facies),biotite(two-mica)K-feldspar granite,two-mica adamellite(transitional facies)and biotite granite(border facies).LA-ICP-MS zircon U-Pb geochronological and petrogeochemical studies are determined.The results show that the zircon 206Pb/238 U weighted average ages of the rocks of the central facise are 210±5Ma and 218.7±3.3Ma,indicating the crystallized-age of the plutons in late Triassic epoch.The granites are high in SiO2(SiO2=65.33% ~74.74%),K2O(K2O =3.82~6.02,K2O/Na2 O =1.27~2.32)and Al2O3(Al2O3=12.87% ~15.19%,A/CNK=0.85~1.17)and low in TiO2(less than 0.33),MgO(MgO=0.16%~1.78%)and Fe2O3(Fe2O3T=1.79%~4.98%),belongs to high K-shoshonite series with metaluminous to slightly peraluminous feature.In addition,they are enriched in total REE contents(123×10-6~363×10-6),with obvious negative Eu anomaly(δEu=0.29~0.60).The trace elements show enrichment in Rb,Th,Sm and Rb/Sr value(0.77~3.56),depletion in Ba,Sr,Ti,Nb,Ta,with the characteristics of S-type granite.Combined with the data of southern margin of Altay,the VAral granitic plutons were formed in the transitional tectonic setting from the post-collisional orogeny to intraplate,derived from partially melted of crust dominated by greywacke contain claystone,and the Koktokay pegmatite No.3vein likely has genetic relationship with it.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2015年第2期339-354,共16页
Acta Geologica Sinica
基金
中国地质调查局区域地质调查项目(编号:1212011120503
1212011120509)资助的成果