Dehydration Melting and Proterozoic Granite Petrogenesis in a Collisional Orogen——A Case from the Svecofennian of Southern Finland  

作　　者：Tom Andersen O.Tapani Rämö 

机构地区：[1]Department of Geosciences,University of Oslo,N-0316,Oslo,Norway [2]Department of Geosciences and Geography,Geology and Geophysics Research Program,University of Helsinki,00014,Helsinki,Finland

出　　处：《Journal of Earth Science》2021年第6期1289-1299,共11页地球科学学刊（英文版）

摘　　要：Dehydration melting of metasupracrustal rocks at mid-to deep-crustal levels can generate water undersaturated granitic melt.In this study,we evaluate the potential of~1.89–1.88 Ga metasupracrustal rocks of the Precambrian of southern Finland as source rocks for the 1.86–1.79 Ga late-orogenic leucogranites in the region,using the Rhyolite-MELTS approach.Melt close in composition to leucogranite is produced over a range of realistic pressures(5 to 8 kbar)and temperatures(800 to 850℃),at 20%–30%of partial melting,allowing separation of melt from unmelted residue.The solid residue is a dry,enderbitic to charnoenderbitic ganulite depleted in incompatible components,and will only yield further melt above 1000–1050℃,when rapidly increasing fractions of increasingly calcic(granodioritic to tonalitic)melts are formed.The solid residue after melt extraction is incapable of producing syenogranitic magmas similar to the Mid-Proterozoic,A-type rapakivi granites on further heating.The granitic fraction of the syenogranitic rapakivi complexes must thus have been formed by a different chain of processes,involving mantle-derived mafic melts and melts from crustal rock types not conditioned by the preceding late-orogenic Svecofennian anatexis.

关 键 词：LEUCOGRANITE rapakivi granite ANATEXIS restite depleted granulite FINLAND 

分 类 号：P534.3[天文地球—古生物学与地层学] P588.121[天文地球—地质学] P542