气候变化领域集成服务门户(CCPortal): Congo River sand and the equatorial quartz factory

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DOI	10.1016/j.earscirev.2019.102918
	Congo River sand and the equatorial quartz factory
	Garzanti E.; Vermeesch P.; Vezzoli G.; Andò S.; Botti E.; Limonta M.; Dinis P.; Hahn A.; Baudet D.; De Grave J.; Yaya N.K.
发表日期	2019
ISSN	0012-8897
卷号	197
英文摘要	A never solved problem in sedimentary petrology is the origin of sandstone consisting exclusively of quartz and most durable heavy minerals. The Congo River offers an excellent test case to investigate under which tectonic, geomorphological, climatic, and geochemical conditions pure quartzose sand is generated today. In both upper and lowermost parts of the catchment, tributaries contain significant amounts of feldspars, rock fragments, or moderately stable heavy minerals pointing at the central basin as the main location of the “quartz factory”. In Congo sand, quartz is enriched relatively to all other minerals including zircon, as indicated by Si/Zr ratios much higher than in the upper continental crust. Selective elimination of old zircons that accumulated radiation damage through time is suggested by low percentages of grains yielding Archean U–Pb ages despite the basin being surrounded by Archean cratonic blocks. Intense weathering is documented by the lack of carbonate grains in sand and by dominant kaolinite and geochemical signatures in mud. In sand, composed almost entirely of SiO2, the weathering effect is masked by massive addition of quartz grains recycled during multiple events of basin inversion since the Proterozoic. Changes in mineralogical, geochemical, and geochronological signatures across Bas-Congo concur to suggest that approximately 10% of the sand supplied to the Atlantic Ocean is generated by rapid fluvial incision into the recently uplifted Atlantic Rise. The Congo River connects with a huge canyon ~30 km upstream of the mouth, and pure quartzose sand is thus funnelled directly toward the deep-sea to feed a huge turbidite fan. Offshore sediments on both sides of the canyon are not derived from the Congo River. They reflect mixed provenance, including illite-rich dust wind-blown from the arid Sahel and augite, hypersthene, and smectite ejected from volcanic centres probably situated along the Cameroon Line in the north. Because mixing of detritus from diverse sources and supply of polycyclic grains almost invariably occurs in the terminal lowland tract of a sediment-routing-system, no ancient sandstone can be safely considered as entirely first-cycle. Moreover, the abundance of pure quartzarenite in the rock record can hardly be explained by chemical weathering or physical recycling alone. The final cleansing of minerals other than quartz, zircon, tourmaline, and rutile requires one or more cycles of chemical dissolution during diagenesis, which operates at higher temperatures and over longer periods than weathering at the Earth's surface. © 2019
英文关键词	Calcite dissolution; Chemical indicators of weathering and recycling; Equatorial weathering; First-cycle versus polycyclic quartzarenites; Provenance analysis; U-Pb zircon geochronology; Volcanic provenance of offshore muds; Zircon weatherability
语种	英语
scopus关键词	chemical weathering; crustal recycling; dissolution; geochronology; mud; provenance; quartz; sandstone; uranium-lead dating; Congo River
来源期刊	EARTH-SCIENCE REVIEWS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/209826
作者单位	Laboratory for Provenance Studies, Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milano, 20126, Italy; London Geochronology Centre, Department of Earth Sciences, University College London, WC1E 6BT, London, United Kingdom; Department of Earth Sciences, MARE – Marine and Environmental Sciences Centre, University of Coimbra, Portugal; MARUM Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany; Geodynamics & Mineral Resources, Royal Museum for Central Africa (RMCA), Leuvensesteenweg 13, Tervuren, 3080, Belgium; Department of Geology and Soil Science (WE13), MINPET, Ghent University, Krijgslaan 281/S8, WE13, Gent, B-9000, Belgium; CRGM Centre de Recherches Géologiques et Minières, 44, Av. de la Démocratie, Kinshasa-Gombe, Congo
推荐引用方式 GB/T 7714	Garzanti E.,Vermeesch P.,Vezzoli G.,et al. Congo River sand and the equatorial quartz factory[J],2019,197.
APA	Garzanti E..,Vermeesch P..,Vezzoli G..,Andò S..,Botti E..,...&Yaya N.K..(2019).Congo River sand and the equatorial quartz factory.EARTH-SCIENCE REVIEWS,197.
MLA	Garzanti E.,et al."Congo River sand and the equatorial quartz factory".EARTH-SCIENCE REVIEWS 197(2019).