Evidence for a Neoproterozoic ocean in south-central Africa from mid-oceanic-ridge type geochemical signatures and pressure-temperature estimates of Zambian eclogites
作者： Timm John , Volker Schenk , Karsten Haase , Erik Scherer , Francis Tembo
DOI: 10.1130/0091-7613(2003)031<0243:EFANOI>2.0.CO;2
关键词: Geology 、 Oceanic crust 、 Metamorphism 、 Eclogite 、 Craton 、 Isochron 、 Subduction 、 Mid-ocean ridge 、 Geochemistry 、 Metamorphic facies
摘要: Precambrian eclogites, metagabbros, and gabbros occur in an similar to200-km-long by 40-km-wide zone central Zambia. Pressure-temperature (P-T) estimates of kyanite-bearing eclogites (kyanite eclogites) throughout the give temperatures 590-750 degreesC at minimum pressures 20 kbar. Phengite-bearing equilibrated 720-755 26-28 kbar show evidence for a clockwise P-T path. These conditions imply low geothermal gradient to8 degreesC/km subduction depth to90 km. The incompatible element patterns to those recent mid-oceanic-ridge basalts, thus are interpreted represent former oceanic crust. indicates cold subducted lithosphere, implying long-lived, fast convergence relatively large (>1000 km) associated ocean basin. A Sm-Nd isochron defines age 595 +/- 10 Ma eclogite facies metamorphism. results that Neoproterozoic suture exists between Congo Kalahari cratons. Suturing occurred during same orogenic cycle formed Zambezi belt is related assembly Gondwana.
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