冈底斯岩基中包体的初步研究

本文综合国内外研究成果对花岗岩中岩石包体进行成因归类,指出对其研究的理论和实际意义。以岩相学为基础,讨论冈底斯岩基中镁铁质包体的类型及形成机理,揭示冈底斯各单元岩浆作用初期的演化过程。

PRELIMINARY STUDY OF THE ENCLAVES IN GANDISE BATHOLITH,XIZANG

Based on the research results in the lab and the field, the enclaves in granitic rocks can be divided into six types of genesis: restite; xenolith; cognate inclusion; residual-magma enclave; immiscible enclave and quenched enclave. There are planty of mafic enclaves in Gandise batholith. The two major types are immiscible enclave and quenched enclave. The quenched enclaves are exposed in C and D units. Their features indicate that this type of enclave represent mixtures of quenched basalts and Ga(?)dise granites. The basalt magma was intruded into the lower of Gandise granitic magma, where it was partially quenched along an interface with overlying granitic magma. The residual liquid in the partially quenched basalts permitted mixing with the overlying magma to form a hybrid zone. This zone was then disaggregated, yiellding the enclaves,and they were dispersed throughout the upper part of Gandise granitic magma chamber. The immiscible enclaves are widely exposed in B,C and D units when the basalt magma intruded into the lower of Gandise granitic magma the heat of the basalt magma diffused to the overlying magma and formed a higher temperature belt in overlying magmaa where it wss separated inito a more mafic and a more silicic facies. This more mafic liquid facies was then dispersed into the uqqer part of Gandise granitic magma chamber and crystallized into the immiscible enclaves.