东昆仑黑海地区加里东期过铝质花岗岩岩石学、地球化学特征及地质意义

Petrological,Geochemical Characteristics and Geological Significance of the Caledonian Peraluminous Granites in Heihai Region,Eastern Kunlun

东昆仑黑海地区发育加里东期过铝质花岗岩（424.0-420.5Ma）,其形成与地壳的发展演化密切相关,主要通过岩相学和地球化学方法对其进行了研究.黑海过铝质花岗岩由黑云母英云闪长岩、黑云母花岗闪长岩、黑云母花岗岩、二云母花岗岩和白云母花岗岩组成.SiO2变化区间为65.32%-75.87%,K2O/Na2O为0.47-1.52,δ为1.09-3.00,为钙碱性-高钾钙碱性系列;A/CNK为1.02-1.31,属于过铝质-强过铝质花岗岩.稀土元素具有轻稀土相对富集和重稀土相对亏损的特征,中等负铕异常.微量元素具有相对选择性富集大离子亲石元素而相对亏损高场强元素的特征.源区参与熔融物质由以变杂砂岩为主,向以变泥质岩为主过渡.结合区域资料,认为黑海过铝质花岗岩是东昆南俯冲增生杂岩楔发生伸展减薄引起地幔物质底侵而促使富硅铝地壳物质发生不同程度部分熔融形成.

Caledonian peraluminous granites （420.5 to 424.0 Ma）, is closely related with the development and evolution of the crust. In Order to study their composition features and formation mechchanism, petrographical and geochemical investigations were carried out. It consist of biotite tonalite, biotite granodiorite, biotite granite, two-mica granite and muscovite granite in Heihai region. The rock types are of de-alkali series and high-K calc-alkaline series （SiO2 =65.32%-75.87%, K2O/Na2 O=0.47-1.52, 8=1.09-3.00）, and be- long to peraluminous granites or strongly peraluminous granites （A/CNK= 1.02-1.31）. REE display relatively LREE-enriched and HREE-depleted characteristics, with moderate Eu negative abnormality. LILE are of relatively selective enrichment and HFS elements are of relatively depletion. The melting materials of source are metagreywacke and metapelite. Based on regional geology, this paper suggests that Heihai peraluminous granites were formed by partial melting of the alumina-silica crust, which was caused by mantle underplating and extension of the southern subduction accretionary complex：