灶火沟早志留世 (436. 8 ～433. 7 Ma) 花岗岩发育于东昆中蛇绿构造混杂岩带中，主要岩石类型为花岗闪长岩和二长花岗岩，其围岩分别为中元古代万宝沟群和奥陶—志留纪纳赤台群。花岗闪长岩和二长花岗岩 w (SiO 2 ) 分别为 56. 12% ～63. 49%和 70. 62% ～76. 54%，均为钙碱性系列。二长花岗岩显示向富碱质过渡的特征，铝饱和指数 A/CNK 为 0. 79 ～ 1. 02，属准铝质—弱过铝质系列，为 I 型花岗岩。花岗闪长岩∑ＲEE 低于二长花岗岩∑ＲEE，两者均具有 LＲEE 相对富集而 HＲEE 相对亏损的相似的右倾球粒陨石标准化配分曲线特征，花岗闪长岩具弱负 Eu 异常，二长花岗岩具强负 Eu 异常; 两者均具有相对富集 LILE 而相对亏损 HFS 的微量元素特征。地球化学特征显示灶火沟花岗岩为岛弧型花岗岩，是原特提斯洋壳向北俯冲引起地幔楔物质底侵东昆仑岛弧下地壳部分熔融的产物，表明东昆仑造山带在早志留世仍处于原特提斯洋壳俯冲消减阶段。

Zaohuogou Early Silurian granite (436. 8 ～433. 7 Ma) dominated by granodiorite and monzogran- ite is located in the central ophiolitic tectonic melange belt of eastern Kunlun． The surrounding rocks are Mesoprot- erozoic Wanbaogou group and Ordovician- Silurian Nachitai group，respectively． The contents of SiO 2 in the grano- diorite and monzogranite are 56. 12% ～63. 49% and 70. 62% ～76. 54%，respectively，belonging to calkaline se- ries． The monzogranite shows the characteristics of the alkaline rocks，and the rocks are metaluminous- peralumi- nous series with A/CNK as 0. 79 ～1. 02，belonging to I- type granites． The ∑ＲEE in granodiorites is lower than in the monzogranites，and both the rocks displayed the characteristics of enrichment in LＲEE and relative loss in HＲEE． The granodiorite has slight negative abnormality in Eu， and both the two rocks are charaterized by depletion in HFS and enrichment in LILE． The geological characteristics reveal that the Zaohuogou granites were island arc granites． They were derived from the partial melting of the lower island arc crust of eastern Kunlun which caused by the underplating of the mantle wedge in the period of the Prototethys oceanic crust subduction． The discovery of Zaohuogou granites indicates that the eastern Kunlun was still in the stage of the Prototethys oceanic crust subduc- tion during the Early Silurian．