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The Distinctive Mineral Combination and the Formation of Native Copper in the Mayang Sandstone‐hosted Native Copper Deposit, Hunan Province, China
Author(s) -
WANG Dapeng,
ZHANG Qian,
LIU Yuping,
YE Lin,
LAN Jiangbo
Publication year - 2014
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.12368_26
Subject(s) - chinese academy of sciences , geochemistry , china , geology , archaeology , geography
The Yuanma Basin, has its maximum length in a NESW direction and extends for nearly 240km between Xuefeng Mountain and Wuling Mountain, is usually studied as a secondary tectonic unit of Xuefeng Mountain district (Chen Haihong, 1993, Qiu Yuanxi, 1999, Wang Fuquan, 2002). Despite the great controversy regarding the evolution of the Yuanma basin, all investigators concur that the Yuanma Basin developed during the Mesozoic to Palaeogene epoch, and the filled sequences can be divided into 3 unconformity-bounded stratigraphic units, i.e. the upper Triassic to Jurassic system,the Cretaceous stratigraphy and the Palaeogene series. The Jinjiang Formation of the upper Cretaceous is wellexposed in the mining area. This Formation, 165m (N) to 728m (S) thick, can be at least divided into 9 cycles,and each cycle has a greenish-grey bottom and a reddishbrown roof. The lithology of the reddish-brown roof is reddish-brown thickly-stratified siltstone and/or politic siltstone, and the reddish-brown color is due to red coatings of hematite and/or goethite. The lithology of the greenish-grey basic rock is dominated by poorly-sorted coarseto medium-grained conglomeratic sandstone and/ or sandstone. The ore bodies are multistory and mainly occur in the greenish-grey beds of the Jinjiang Formation, and a single ore-body is stratified or lentoid. The main ore mineral is native copper (more than 90% of the total ore output) and chalcosine. Little chalcocite is symbiotic with native copper, but occurs as major ore mineral in several orebeds near to the earth's surface. In the layer like ore-bodies, native copper occurs as 3 types: 1 The copper, very fine-grained or vermiform, uniformly expands in finely crystalline siliceous fragments. We observed more than 300 fragments in 34 samples, in which did not find the copper intersects the scraps. This mining structure show that the mineralization in siliceous fragments must form in the origin area. 2 In most cases, irregular or grained native copper is important as cement and usually replace sericitized feldspar scraps, rock fragment or even other interstitial matter. The mineral associated with native copper is extremely abundant and characteristic and will be detailed described below. 3 Nearly the surface of the earth, native copper formed 3g~40kg tabular or dendritic aggregate with gypsum in faults.