The metamorphic evolution of the Paleoproterozoic (Birimian) volcanic Ashanti belt (Ghana, West Africa)

John, Timm; Klemd, Reiner; Hirdes, W.; Loh, Geoffrey

doi:10.1016/s0301-9268(99)00024-8

Cited by 99 publications

(72 citation statements)

References 33 publications

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“…These values are also comparable to a Belt-type granite sample reported in John et al (1999), with 3.59 wt% CaO, 4.58 wt% Na 2 O, 1.89 wt% K 2 O, and 50 ppm Rb. The published CaO content of this Belt-type sample is, thus, far higher than the CaO contents of the samples analyzed here.…”

Section: Granite Classification and Provenancesupporting

confidence: 86%

Petrography, geochemistry, and alteration of country rocks from the Bosumtwi impact structure, Ghana

Karikari

Ferrière

Koeberl

et al. 2007

Meteorit & Planetary Scien

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Abstract-Samples of the country rocks that likely constituted the target rocks at the 1.07 Myr old Bosumtwi impact structure in Ghana, West Africa, collected outside of the crater rim in the northern and southern parts of the structure, were studied for their petrographic characteristics and analyzed for their major-and trace-element compositions. The country rocks, mainly meta-graywacke, shale, and phyllite of the Early Proterozoic Birimian Supergroup and some granites of similar age, are characterized by two generations of alteration. A pre-impact hydrothermal alteration, often along shear zones, is characterized by new growth of secondary minerals, such as chlorite, sericite, sulfides, and quartz, or replacement of some primary minerals, such as plagioclase and biotite, by secondary sericite and chlorite. A late, argillic alteration, mostly associated with the suevites, is characterized by alteration of the melt/glass clasts in the groundmass of suevites to phyllosilicates. Suevite, which occurs in restricted locations to the north and to the south-southwest of the crater rim, contains melt fragments, diaplectic quartz glass, ballen quartz, and clasts derived from the full variety of target rocks. No planar deformation features (PDFs) in quartz were found in the country rock samples, and only a few quartz grains in the suevite samples show PDFs, and in rare cases two sets of PDFs. Based on a total alkali element-silica (TAS) plot, the Bosumtwi granites have tonalitic to quartz-dioritic compositions. The Nb versus Y and Ta versus Yb discrimination plots show that these granites are of volcanic-arc tectonic provenance. Provenance studies of the metasedimentary rocks at the Bosumtwi crater have also indicated that the metasediments are volcanic-arc related. Compared to the average siderophile element contents of the upper continental crust, both country rocks and impact breccias of the Bosumtwi structure show elevated siderophile element contents. This, however, does not indicate the presence of an extraterrestrial component in Bosumtwi suevite, because the Birimian country rocks also have elevated siderophile element contents, which is thought to result from regional hydrothermal alteration that is also related to widespread sulfide and gold mineralization.

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Section: Granite Classification and Provenancesupporting

confidence: 86%

Petrography, geochemistry, and alteration of country rocks from the Bosumtwi impact structure, Ghana

Karikari

Ferrière

Koeberl

et al. 2007

Meteorit & Planetary Scien

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“…These are too small in size to have been the major source of supply for such a large basin as the LGB protolith. Larger occurrences of silicic igneous rocks as well as signs of high-grade metamorphism of this age group are found elsewhere on the Earth, especially in South America in the Transamazonian belts and related belts in Western and Central Africa (Dada, 1998;Feybesse et al, 1998;Hartmann et al, 1999;John et al, 1999;Norcross et al, 2000;Plá Cid et al, 2000;Nomade et al, 2002). Also, larger occurrences of this age group are found in Eastern Asia in Korea and the North China Craton (Cheong et al, 2000;Zhao et al, 2000).…”

Section: Tectonic Consequences and Correlationmentioning

confidence: 91%

Evolution of migmatitic granulite complexes: Implications from Lapland Granulite Belt, Part II: Isotopic dating

Tuisku¹,

Huhma²

2006

Bull Geol Soc Finland

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The migmatitic metapelites of the Lapland granulite belt (LGB) in the NE part of the Fennoscandian Shield represent an arc-related greywacke basin metamorphosed in the granulite facies. Detrital zircons from migmatitic metapelites are derived from 1.94 etrital zircons from migmatitic metapelites are derived from 1.94 zircons from migmatitic metapelites are derived from 1.94 derived from 1.94 − 2.9 Ga old acid source rocks (U-Pb SIMS ages). The clustering of detrital zircon ages between 1.97 and 2.2 Ga is problematic, because abundant felsic crust of this age is absent in the shield. The metasediments are characterized by Sm-Nd model ages of ca. 2.3 Ga. A younger, 1905 − 1880 Ma population of homogeneous zircons was formed during regional metamorphism. The peak high-grade metamorphism took place at ~1900 Ma and the latest chronological record from subsequent decompression and cooling phase is from ca. 1870 Ma. The norite-enderbite series of the LGB represents arc-magmas, which were intruded into the metasediments at ~1920 − 1905 Ma ago according to zircon U-Pb ages and were probably an important heat source for metamorphism. Older, zoned zircon grains in a quartz norite vein, initial ε Nd values of 0 to +1 and the continuous spectrum of LILE enrichment in the enderbite-series probably reflect assimilation of metasediments by magmas. Monazite U-Pb ages of migmatitic metasediments in the range 1906 − 1910 ± 3 Ma overlap the late stage of enderbite intrusion and growth of early metamorphic zircons. Garnetwhole rock Sm-Nd ages from leucosomes in the range 1880 − 1886 ± 7 Ma are concurrent with the growth of the youngest metamorphic zircons and probably indicate the crystallization of leucosomes or the influence of a fluid liberated from them. Isotopic and petrologic data reveal that the evolution of Lapland Granulite belt from the erosion of source rocks to the generation of a sedimentary basin, its burial, metamorphism and exhumation took place within ca. 60 Ma.

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“…The terranes were accreted and cratonised during the Eburnean orogeny, a period of SE to NW directed crustal shortening, metamorphism and magmatic accretion (Oberthür et al, 1998;Feybesse et al, 2006). Peak metamorphic conditions are widely reported as amphibolite facies (500-600°C; 4-6 kbar; John et al, 1999;White et al, 2013), with a retrograde greenschist facies overprint (Hirdes et al, 1996). The Birimian terranes formed over a period of ~180 Ma (Perrouty et al, 2012;White et al, 2014 and references therein;Parra-Avila et al, 2015).…”

Section: Geological Settingmentioning

confidence: 99%

“…This period is divided into two phases. Though there is regional variation, broadly the Eoeburnean (also known as Eburnean I or the Tangaean; 2266-2150 Ma) precedes the Eburnean (2216-1980 (Taylor et al, 1992;Dia et al, 1997;Loh et al, 1999;Allibone et al, 2002;Gueye et al, 2007;Tshibubudze et al, 2009;Hein, 2010;de Kock et al, 2011). The Eoeburnean consists of volcanism, granitoid emplacement and fold, thrust tectonics, and is interpreted by Tshibubudze et al, (2015) to be a single diachronous event across the Birimian.…”

Section: Geological Settingmentioning

confidence: 99%

Discriminating fluid source regions in orogenic gold deposits using B-isotopes

Lambert-Smith

Rocholl

Treloar

et al. 2016

Geochimica et Cosmochimica Acta

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The genesis of orogenic gold deposits is commonly linked to hydrothermal ore fluids derived from metamorphic devolatilisation reactions. However, there is considerable debate as to the ultimate source of these fluids and the metals they transport. Tourmaline is a common gangue mineral in orogenic gold deposits. It is stable over a very wide P-T range, demonstrates limited volume diffusion of major and trace elements and is the main host of B in most rock types. We have used texturally resolved B-isotope analysis

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The metamorphic evolution of the Paleoproterozoic (Birimian) volcanic Ashanti belt (Ghana, West Africa)

Cited by 99 publications

References 33 publications

Petrography, geochemistry, and alteration of country rocks from the Bosumtwi impact structure, Ghana

Petrography, geochemistry, and alteration of country rocks from the Bosumtwi impact structure, Ghana

Evolution of migmatitic granulite complexes: Implications from Lapland Granulite Belt, Part II: Isotopic dating

Discriminating fluid source regions in orogenic gold deposits using B-isotopes

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