Formation of the Archaean greenstone belt

1.热变质岩中成岩矿物的EPMA分析即使在单一的变质玄武岩中，角闪石的化学成分也有很大的不同。这表明，在该地区发生的热变质作用期间，没有达到平衡。XRF整体化学分析对花岗岩类和变质火山岩进行了XRF分析。花岗岩类以熔岩和矿体的形式出现。它们在岩石学上可分为四种类型。常量元素化学在不同类型的岩石之间是不同的，在属于同一岩石类型的岩体之间也是不同的。每个花岗岩类物质可能有不同的侵位历史。结论肯尼亚太古宙绿岩带中的花岗岩类侵位于先前存在的火山岩和沉积岩的浅部。接触晕的热结构取决于花岗岩块的岩石学特征和形态。太古代克拉通上部为花岗岩-绿岩组合，下部为花岗岩-高品位岩石组合。

1. EPMA analyzes of rock-forming-minerals in the thermally metamorphosed rocksEPMA analyzes are made on minerals in metavolcanics and metasediments. Chemical composition of amphiboles varies considerably even in a single metabasalt. This suggests that the equilibrium is not attained during the thermal metamorphism that took place in this area.2. XRF bulk chemical analyzesXRF analyzes are made on granitoids and metavolcanics. Granitoids occur as batholiths and as stocks. They are petrographically classified into four types. Major element chemistry differs between rocks of different type and also differs between rock masses belonging to the same rock type. Each of the granitoid masses probably has a different history of its emplacement.3. ConclusionThe granitoids in the Archaean greenstone belt in Kenya emplaced in the shallow level of preexisting volcanic and sedimentary rocks. Thermal structures of the contact aureole depend on petrologic characteristics and shapes of the granitoid mass. The granitoid-greenstone association formed the upper part and the granitoid-high grade rock association formed the lower part in the Archaean Craton.