【摘要】 羌塘中部各拉丹冬岩体主要由二长花岗岩组成,其单颗粒锆石U-Pb年龄为40±3Ma,Rb-Sr等时线年龄为47±0·4Ma,斜长石、角闪石、黑云母K-Ar年龄分别为37·1Ma、48Ma和45·8Ma,形成于始新世。岩石富碱高,高钾(K2O>Na2O),属高钾钙碱性系列。微量元素以富集LREE、LILE(Th、U等),相对亏损HFSE为特征,(87Sr/86Sr)i为0·70701~0·70724,εNd(t)为-6·0~-4·1,δ18O值为8·18‰~9·01‰,构造背景为火山弧花岗岩。55Ma以来,印度板块与欧亚板块碰撞,大范围抬升,青藏高原在经历近南北向挤压缩短的过程中,可能在羌塘地体上产生了平行于主压应力方向的张性构造,导致了各拉丹冬花岗岩体侵位。应为青藏高原隆升在北羌塘陆块所表现的构造热事件之一。更多还原

【Abstract】 The Geladandong intrusive body mainly consists of monzonitic granite, with the single zircon U_Pb age being 40±3 Ma, the Rb_Sr isochron age of the rock being 47±0.4 Ma, and the K_Ar ages of plagioclase, hornblende and biotite being 37.1 Ma, 45.8 Ma, 48 Ma, respectively. The rock body was formed in Eocene. The rocks have high content of alkali and potash （K₂O>Na₂O）, belonging to high_potash calc_alkalic series. The trace elements are characterized by enrichment of LREE, LILE （Th, U） and depletion of HFSE. The 87 Sr/ 86 Sr ratios, the ε Nd （t）ratios and the δ 18 O values range from 0.70701 to 0.70724, -6.0 to -4.1, and 8.18‰ to 9.01‰, respectively. These data prove that the tectonic setting is volcanic island arc granite. The collision of the Indian plate with the Eurasian plate led to the large_scale uplift from 55 Ma. During the nearly SN_trending compression and shortening, Qinghai_Tibet plateau probably produced a tensile structure parallel to the main stress in Qiangtang terrane, leading to the emplacement of Geladandong granite. This is one of the hot tectonic events produced in northern Qiangtang terrane by the uplift of Qinghai_Tibet plateau.更多还原