Fluid metasomatic genesis of stratiform skarn in the Suoerkuduke Cu-Mo deposit,East Junggar,NW China |
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| Institution: | 1. Key Laboratory of Mineral Resources, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. Université de Toulouse, CNRS, Géosciences Environnement Toulouse, Institut de Recherche pour le Développement, Observatoire Midi-Pyrénées, 14 Av. Edouard Belin, F-31400 Toulouse, France;2. Azumah Resources Ghana limited, PMB CT452, Cantonments, Accra, Ghana;3. IFAN Cheikh Anta Diop, Dakar, Senegal;4. Centre for Exploration Targeting, School of Earth and Environment, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;1. UQAC, Université du Québec à Chicoutimi, 555 Boulevard de l''Université, Chicoutimi, Québec G7H 2B1, Canada;2. LAMEQ, Laboratoire de Métallogénie Expérimentale et Quantitative, Université du Québec à Chicoutimi (UQAC), 555 Boulevard de l''Université, Chicoutimi, Québec G7H 2B1, Canada;3. SEMAFO Inc. Société d''Exploitation Minérale en Afrique de l''Ouest, 100 Boulevard Alexis-Nihon, 7e Étage, St-Laurent, Québec H4M 2P3, Canada;1. Centre for Exploration Targeting and ARC Centre of Excellence for Core to Crust Fluid Systems, School of Earth and Environment, The University of Western Australia, Crawley, WA 6009, Australia;2. Géosciences Environnement Toulouse, CNRS, IRD, OMP, University of Toulouse, Toulouse, France;3. Avocet Mining PLC and Goldbelt Resources, Ouagadougou, Burkina Faso;4. GeoRessources, CNRS–CREGU, Université de Lorraine, France;1. Nuclear Materials Authority, P. O. Box 530, El Maadi, Cairo, Egypt;2. Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University, Fukuoka 819-0395, Japan |
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| Abstract: | Stratiform skarns associated with ore deposits are widespread in the north of East Junggar, particularly in the Suoerkuduke Cu-Mo deposit. The Suoerkuduke stratiform and stratoid skarns are hosted by Devonian intermediate-mafic volcanic and pyroclastic rocks, mainly andesite, andesitic porphyry and tuffaceous sandstone, without carbonate or calcareous rocks. The skarns consist of dominant andradite-grossular, epidote, diopside-hedenbergite and minor actinolite, quartz, magnetite and metallic sulfides. The garnet and epidote composition, especially Fe3 + and Al contents, is largely a function of the bulk composition and physicochemical environment (particularly fO2) during crystallization. Such mineralogy indicates a relatively oxidizing environment and medium acidity of solution during skarnization.The Suoerkuduke skarns are distinct from typical contact metasomatic skarn in wall rock, as no carbonate or calcareous rocks were found, and differ in the distribution patterns of skarn zonation in that gradually weakened skarn zones are not quite symmetrically distributed on both sides of the alteration center (a garnet skarn). Abundant remnants of andesite, andesitic porphyry and tuffaceous sandstone in the weakened skarn zone indicate that the protolith of the skarn is andesite, andesitic porphyry and tuffaceous sandstone. Magmatic water, meteoric and seawater are involved in skarn alteration. Moyite and granitic porphyry are not coeval with skarn, and their emplacement resulted in the hornfelization of wall rock instead of skarnization, and themselves keep away from skarn alteration. Therefore, there was probably a huge batholith supplying magmatic fluid for skarn formation. Mass balance estimates suggest that hydrothermal fluid must contribute a portion of Ca and Fe to ensure sufficient supply for skarn formation in the absence of local carbonate and calcareous rocks. In conclusion, the stratiform skarns in the Suoerkuduke are products of intermediate-mafic volcanic and pyroclastic rocks metasomatised by hydrothermal fluid that probably leached calcareous wall rock during ascent. |
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