青海扎日加地区分布有大量中酸性侵入岩,岩性组合主要由中细粒黑云母花岗闪长岩、斑状黑云母二长花岗岩、细粒正长花岗岩3类组成,岩石中SiO2(67.38％ ～ 76.03％)含量逐渐增高,Al2O3(13.62％～15.48％)、CaO(0.6％～3.02％)、MgO(0.12％～ 1.69％)、K2O(3.00％～4.51％)、TiO2(0.05％～0.66％),碱度率AR=2.01～3.59,大于1;里特曼指数δ在1.42～ 1.98,属过铝质—钙碱性或碱性花岗岩;稀土总量中等(∑REE=83.09×10-6～ 222.27×10-6),稀土元素标准化曲线为向右陡倾的富集型曲线,铕处“V”型较明显,同时各曲线近于平行;岩石中Rb、Th明显富积,Ba、Nb、Hf、Zr不同程度亏损,以上特征显示岩石具壳型花岗岩特征.在斑状黑云母二长花岗岩中获得LA-ICP-MS锆石U-Pb年龄为(203.34±0.72) Ma,表明巴颜喀拉山浊积盆地区的同碰撞花岗岩发生在晚三叠世并持续至早侏罗世,在构造阶段上属于从挤压构造体制向伸展构造体制转化的转折期.%Intensive intermediate-acid intrusive outcropped in the Zharijia area,Qinghai Province.The lithological association is mainly composed of three types of intrusive,i.e.,medium-fine grain biotite granodiorite,porphyritic biotite monzonitic granite and fine grained syenogranite with increasing contents of SiO2 (67.38％ ～ 76.03％),Al2O3 (13.62％ ～ 15.48％),CaO (0.6％ ～ 3.02％),MgO (0.12％～1.69％),K2O(3.00％ ～4.51％),and TiO2(0.05％ ～0.66％).The alkalinity ratio ranges from 2.01 to 3.59 and Rittman index ranges from 1.42 to 1.98,which indicate the intrusives are peraluminous calcium-alkali or alkaline granite.The total REE content is moderate with values of from 83.09× 10-6 to 222.27× 10-6,and the normalized REE pattern shows the intrusives are enriched in LREE and have obvious Eu anomaly.Rb and Th elements in rocks are obviously accumulated,while Ba,Nb,Hf and Za elements are loss to some degree.The U-Pb dating result of zircon mineral collected from porphyritic biotite monzonitic granit by LA-ICP-MS method is (203.34±0.72) Ma,which indicates that the syn-collision stage granite intrusions in the Bayankalashan turbidite basin area were intruded in late Triassic period and lasted until early Jurassic period.In tectonic setting,the intrusions occurted in the transition period of from the compressive tectonic regime to extensional tectonic regime.
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