青海同仁、泽库地区三叠纪岩浆岩形成时代及其成因研究

发布时间：2018-06-04 01:18

本文选题：西秦岭 + 三叠纪岩浆岩　；参考：《合肥工业大学》2015年硕士论文

【摘要】：秦-祁-昆结合部广泛分布中生代岩浆活动,但是其岩石成因和形成构造环境仍存在争议。本文对西秦岭同仁-泽库地区三叠纪岩浆岩进行了地质年代学和地球化学研究。同仁-泽库地区三叠纪岩浆岩由安山岩。英安岩、花岗斑岩和花岗闪长岩组成,SHRIMP锆石U-Pb定年显示同仁安山岩、泽库安山岩、泽库花岗斑岩分别形成于240.1±2.4Ma、245.0±2.8Ma、240.5±3.6Ma,都形成于中三叠世。同仁-泽库地区三叠纪岩浆岩都富集大离子亲石元素(如Th、U、Pb)和轻稀土元素,但是亏损高场强元素和重稀土元素,.表现出类似弧的微量元素配分型式。安山岩和花岗闪长岩具有较高的MgO、Cr、Ni含量、Mg#值,低K2O/Na2O比值,且表现出高87Sr/86Sr初始值(0.7083-0.7084)、低εNd(t)值(-7.52～-6.94)和锆石εHf(t)值(-5.58～-1.70),这表明其源自富集岩石圈地幔部分熔融,可能存在少量地壳物质卷入。相对于安山岩和花岗闪长岩,花岗斑岩的MgO、Cr、Ni含量和Mg#值更低,具有更高的K2O/Na2O比值。除了一颗新生锆石具有正的εHf(t)值(+4.1)外,花岗斑岩其他年轻锆石εHHf(t)值变化于(-14.2--9.1)；另外,花岗斑岩具有中-古元古代和晚太古代继承锆石,他们εHf(t)值变化于-7.4～-2.5。我们推测花岗斑岩源自下地壳部分熔融岩浆和富集地幔熔融产生岩浆混合。同仁、泽库地区中三叠世岩浆活动形成于古特提斯洋向北俯冲环境下。
[Abstract]:Mesozoic magmatism was widely distributed in the Qinhuan-Qi-Kun junction, but its petrogenesis and tectonic environment were still controversial. The geochronology and geochemistry of Triassic magmatic rocks in the Tongren-Zecu area of the West Qinling Mountains have been studied in this paper. Triassic magmatic rocks from andesite in Tongren-Zecu area. The shrimp zircon U-Pb dating of dacite, granitic porphyry and granodiorite shows that the Tongren andesite and the Zecu granitic porphyry were formed in 240.1 卤2.4 Ma-245.0 卤2.8 Ma-0. 5 卤3.6 Ma, all of them were formed in the Middle Triassic. The Triassic magmatic rocks in the Tongren Zecu area are rich in large ion lithophile elements (such as Thu U Pb) and light rare earth elements, but are depleted of high field strength elements and heavy rare earth elements. The distribution pattern of trace elements is similar to arc. Andesite and granodiorite have high Mg# value and low K2O/Na2O ratio, and show high initial 87Sr/86Sr value of 0.7083-0.7084 ~ (+) -7.52 ~ (-6.94) and zircon 蔚 Hft) -5.58 ~ 1.70 ~ (-1.70), which indicates that it originated from partial melting of the lithosphere and there may be a small amount of crustal involvement in the crust. Compared with andesite and granodiorite, granitic porphyry has lower content of Mg# and higher K2O/Na2O ratio. With the exception of a new zircon with positive 蔚 Hftt (4.1), the other young zircons of granitic porphyry changed from -14.2--9.1, and granitic porphyry from Meso-Paleoproterozoic and late Archaeozoic inherited zircon, their 蔚 Hft) values varied from -7.4 to -2.5. We speculate that granitic porphyry originated from partial melting magma in lower crust and magmatic mixing from enriched mantle melting. Tongren, the Middle Triassic magmatism in Zecu area was formed in the northward subduction of the PaleoTethys Ocean.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P597.3;P588.1

【相似文献】