Post-collisional potassic granitoids from the southern and northwestern parts of the Late Neoproterozoic East African Orogen: a review

作者: Dirk Küster , Ulrich Harms

DOI: 10.1016/S0024-4937(98)00031-0

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摘要: Abstract Potassic metaluminous granitoids with enrichments of HFS elements constitute part widespread post-collisional magmatism related to the Late Neoproterozoic Pan-African orogeny in northeastern Africa (Sudan, Ethiopia, Somalia) and Madagascar. The plutons were emplaced between 580 470 Ma comprise both subsolvus hypersolvus biotite–granite, biotite–hornblende–granite, quartz–monzonite quartz–syenite. Pyroxene-bearing are subordinate. Basic dikes enclaves monzodioritic composition locally associated granitoid plutons. Granitoids pre-Neoproterozoic crust have Sri-ratios 0.7060 0.7236 eNd(t) values −15.8 −5.6 while those in, or close contact with, juvenile lower (0.7036–0.7075) positive (4.6). However, it is unlikely that potassic represent products crustal melting alone. association basic magmas derived from subduction-modified enriched mantle sources strongly suggests hybrid produced by interaction mixing melts crust. most intense period this occurred 585 540 Ma, largely coeval HT granulite facies metamorphism Madagascar amphibolite retrogression (Somalia, Sudan). Granitoid high-grade probably lithospheric thinning, magmatic underplating relaxation. emplacement granites continued until about implies several pulses different phases uplift cooling. temporally spatially high-K calc-alkaline which they share many petrographical, geochemical isotopical similarities, except incompatible element enrichments. resemblance indicates a petrogenesis granite associations.

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