Formation of the Archaean greenstone belt

太古宙绿岩带的形成

• 批准号: 07640638
• 负责人: HOSHINO Mitsuo
• 金额: $ 1.47万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640638/
• 关键词: Kenya; Greenstone belt; Precambrian; Archaean; Thermal metamorphism; Granitoid; Metamorphic rocks; Craton

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.

1.热变质岩中造岩矿物的EPMA分析EPMA分析是对变火山岩和变质沉积岩中的矿物进行的。即使在单一变玄武岩中，角闪石的化学成分也有很大差异。这表明该地区发生的热变质作用并未达到平衡。2． XRF 整体化学分析 XRF 分析是针对花岗岩和变火山岩进行的。花岗岩以岩基和岩体形式出现。它们按岩相学分为四种类型。不同类型的岩石之间的主要元素化学成分不同，属于同一岩石类型的岩体之间的主要元素化学成分也不同。每个花岗岩体可能有不同的侵位历史。3．结论肯尼亚太古宙绿岩带中的花岗岩位于先存火山岩和沉积岩的浅层中。接触光环的热结构取决于岩石学特征和花岗岩体的形状。太古宙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。

项目成果

地学団体研究会: "新版地学事典(項目執筆)" 平凡社, 1443 (1996)

地球科学组研究组：《新版地球科学百科全书（条目书写）》平文社，1443（1996）