Formation of the Archaean greenstone belt

1. 对热变质岩中的造岩矿物进行了EPMA分析，对变质火山岩和变质沉积物中的矿物进行了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。这说明该区在热变质作用中未达到平衡。XRF大宗化学分析对花岗岩类和变质火山岩进行了XRF分析。花岗岩以岩基和岩块的形式出现。它们在岩石学上可分为四类。不同类型岩石的主元素化学性质不同，同一类型岩体的主元素化学性质也不同。每一个花岗岩块可能都有不同的就位历史。结论肯尼亚太古宙绿岩带花岗岩类侵位于先存火山岩和沉积岩的浅层。接触光圈的热结构取决于岩石学特征和花岗质团块的形状。太古宙克拉通上部为花岗质-绿岩组合，下部为花岗质-高品位岩组合。

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.