GEOCHEMISTRY OF A PSEUDO-GOSSAN DEVELOPED ON A BLACK SHALE-DOLERITE CONTACT, KILLARA, WESTERN-AUSTRALIA

被引:16
作者
BUTT, CRM
机构
[1] C.S.I.R.O., Division of Mineralogy, W.A. 6014, Private Bag, P.O., Wembley
关键词
D O I
10.1016/0375-6742(79)90020-7
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
Ironstones from Killara, 56 km northeast of Meekatharra, Western Australia, contain up to 1800 ppm Cu or up to 600 ppm Zn. A Cu anomaly is shown by the plus 8 and 8 to 36-mesh fractions of the soils but no indication is given by the finer fractions. No Zn anomaly is shown by any soil size fraction. Closely spaced percussion drilling along the Cu anomaly showed that the ironstones overlie carbonaceous shales intruded by metadolerites; the maximum Cu content of these rocks is 190 ppm. The shales and, in particular, the dolerites have traces of sulphides, mostly primary and secondary pyrite and, in places, chalcopyrite. The highest Cu contents in the weathered zone occur mostly at contacts between the shales and dolerites, where copper is concentrated in iron oxides and, to a lesser extent, manganese oxides. On artificial weathering, the shales and dolerites give pH readings of 4.3 and 7.0, respectively; the optimum redox conditions for the coprecipitation of copper with goethite and the precipitation of manganese oxides appear to occur close to the contacts, at the interface between the two environments. The absence of the common pathfinder elements and the lack of a hydromorphic dispersion halo around the ironstones are indicative of pseudo-gossans but are not diagnostic criteria. However, these features may assist in determining priorities in the selection of drilling targets. © 1979.
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页码:131 / 156
页数:26
相关论文
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