EXPERIMENTAL STUDY ON FUSION OF TIN-BEARING GRANITES IN GUANGXI,SOUTHERN CHINA

Experiments have been carried out for studying the melting characteristics of two representative types of granite complexes relating to tin ore deposits in Guangxi. The curves of the beginning melting of the Longxiangai porphyritic biotite granite (LPBG), the Longxiangai granular biotite granite (LGBG), the margin phase and central phase of the rocks of the Pinyin granite (MPPG and CPPG) are determined by the experiments. The results of the experiments show that the temperature of the beginning melting points of the tin -bearing granite not only depends on the type and features of the rocks, but also varies with the total water vapour pressure (PH2O) and the one of the different granites decrease with the increasing pressure. In different ranges of the pressure,the variance gradient of the beginning melting points sharply varies. When PH2O is less than or equal to 136 MPa, the beginning melting temperatures of LPBG somewhat lower than those of LGBG ;Whe P H2O is larger than 136MPa,The beginning temperatures of LPBG are higher than those of LGBG. The beginning teperatures of CPPG are always higher than those of MPFG at the conditions of PH2O from 75 to 250 MPa.

与超大型锡矿床相关的花岗岩熔融实验结果及其成矿学意义

在６００～８５０℃，７５～３００ＭＰａ条件下对与个旧超大型锡（多金属）矿床密切相关的个旧复式花岗岩体，和与大厂长坡－铜坑、龙头山２个超大型锡（多金属）矿床密切相关的龙箱盖复式花岗岩体进行系统的实验研究。其结果表明，不仅形成这２个著名复式花岗岩的岩浆性质及岩浆的演化规律有明显的差异，而且形成同一个复式岩体的岩浆的性质及其演化特点亦有明显的不同。个旧花岗岩浆中，形成老卡岩体的岩浆固相线位置低，具有共结岩浆性质，而形成马松、龙岔河岩体的岩浆固相线位置稍高，具有近共结花岗岩浆的特点；形成龙箱盖复式花岗岩的岩浆在性质上有所不同，其固相线位置较高。这些研究结果表明，２类超大型锡矿床的成矿花岗岩浆的性质、起源与演化规律存在明显的差异，这些差异可能是造成这２个复式花岗岩体在超大型锡矿床形成过程中所起的作用不同的重要原因之一。