No abstract

Please cite this article as: Markwitz, V., Hein, K.A.A., Miller, J.,Compilation of West African mineral deposits: spatial distribution and mineral endowment, Precambrian Research (2015), http://dx. Abstract 20The West African Craton is highly endowed in minerals, and their spatial and temporal 21 distribution varies from single to multi-phase mineralization events. They are broadly related 22 to three major tectono-metallogenic elements and formed during distinct mineral epochs: 23(1) In both Archean Shields (Kénéma-Man and Reguibat) and Paleoproterozoic domains 24 (Baoulé-Mossi, Eglab). These are characterized by giant iron ore deposits that formed 25 between ca. 2.5 -2.3 Ga, nearly all gold, porphyry copper, lead-zinc and sedimentary 26 manganese ore that developed between 2.2 -2.1 Ga, and primary diamonds that formed 27 between two intervals at ca. 2.2 -2.0 Ga and in the Mesozoic. 28(2) Across Pan-African and Variscan belts. These are distinguished by major Precambrian 29 IOCG's, copper-gold that formed at ca. 2.1 Ga and approx. 680 Ma, and Neoproterozoic 30 sedimentary iron ore and phosphate deposits. 31 (3) Within intracratonic and coastal basins. These include the development of Cenozoic 32 lateritic bauxites over Mesozoic dolerites, Tertiary / Quaternary mineral sands deposits, 33 oolitic iron ore and sedimentary phosphate deposits. 34 Geological, spatial and temporal correlations using the multi-commodity West African 35 Mineral Deposit Database highlight that gold and non-gold commodities formed in multiple 36 phases. This commenced in the Liberian Orogeny (2.9 -2.8 Ga) with the enrichment of iron 37 ore, nickel sulphides, diamonds and gold in the earth's crust. The pre-Eburnean or Tangaean-38 EoEburnean-Eburnean I Event yielded gold, and the major Eburnean Orogeny yielded gold, 39 iron ore, manganese, diamonds, magmatic nickel sulphides, copper-gold, lead-zinc, and REE 40 minerals. Throughout the Pan-African event sedimentary manganese deposits, lead-zinc, REE 41 minerals, sedimentary phosphates, and again gold were formed. Primary diamonds and 42 magmatic nickel sulphides are related to the break-up of Gondwana, followed by an intense 43 Page 3 of 87A c c e p t e d M a n u s c r i p t lateritic weathering period that formed bauxite deposits along the craton margin.

Abstract. Continental crustal rocks, now structurally beneath the allochthonous Samail ophiolite, underwent blueschist to eclogite facies metamorphism prior to the emplacement of the Oman ophiolite onto the Arabian margin. The recognition of a major low angle fault within this polydeformed and polymetamorphosed sequence of metacarbonates, metabasites, quartzites and quartz mica schists greatly simplifies the interpretation of the structure and metamorphic zonation within the Saih Hatat window, NE Oman. Carpholite-bearing upper plate rocks consist of pre-Permian to Jurassic rocks that have been folded into large recumbent nappe structures which exhibit a marked increase in deformation intensity toward the boundary with the lower plate. The lower plate rocks have higher peak pressure and temperature assemblages; they are exposed in two windows separated by Jabal Abu Daud. Although more intensely deformed, the lower plate rocks are recognizable as metamorphosed continental platform sediments. Fold axes are parallel to the regional NNE-SSW lineation. Sense of shear indicators yield a transport direction of south over north in the lower plate, opposite to the sense of motion inferred for the emplacement of the ophiolite. Lower plate eclogite-facies metabasalts are only preserved in kilometer-scale megaboudins found in the easternmost window at As Sifah. These metamorphic assemblages along with their remnant eastwest fabrics define the existence of a short-lived, Arabian platform-directed, nascent subduction zone. The stretching lineafion elsewhere within the upper and lower plates, the Hatat Schist (the basement), and the metamorphic sole of the ophiolite is consistently NNE-SSW, suggesting that the exhumation of high-pressure metamorphic rocks of Saih Hatat is related to the ophiolite obducfion. Exhumation of the high pressure rocks was accompanied by intense deformation involving regional-scale fold nappes in a convergent margin setting. The geotherm remained suppressed for a period (>30 Myr) greater than the thermal relaxation time of the crust. The geometric and thermal constraints from Oman may be applicable to the general problem of the formation and preservation of high-pressure, lowtemperature rocks.

The generation and evolution of Earth's continental crust has played a fundamental role in the development of the planet. Its formation modified the composition of the mantle, contributed to the establishment of the atmosphere, and led to the creation of ecological niches important for early life. Here we show that in the Archean, the formation and stabilization of continents also controlled the location, geochemistry, and volcanology of the hottest preserved lavas on Earth: komatiites. These magmas typically represent 50-30% partial melting of the mantle and subsequently record important information on the thermal and chemical evolution of the Archean-Proterozoic Earth. As a result, it is vital to constrain and understand the processes that govern their localization and emplacement. Here, we combined Lu-Hf isotopes and U-Pb geochronology to map the four-dimensional evolution of the Yilgarn Craton, Western Australia, and reveal the progressive development of an Archean microcontinent. Our results show that in the early Earth, relatively small crustal blocks, analogous to modern microplates, progressively amalgamated to form larger continental masses, and eventually the first cratons. This cratonization process drove the hottest and most voluminous komatiite eruptions to the edge of established continental blocks. The dynamic evolution of the early continents thus directly influenced the addition of deep mantle material to the Archean crust, oceans, and atmosphere, while also providing a fundamental control on the distribution of major magmatic ore deposits. crustal evolution | lithosphere | architecture | mantle plumes | Ni-Cu-PGE deposits