Constraints on the composition of ore fluids and implications for mineralising events at the Cleo gold deposit,Eastern Goldfields Province,Western Australia

The Cleo gold deposit, 55 km south of Laverton in the Eastern Goldfields Province of Western Australia, is characterised by banded iron‐formation (BIF)‐hosted ore zones in the gently dipping Sunrise Shear Zone and high‐grade vein‐hosted ore in the Western Lodes.There is evidence that gold mineralisation in the Western Lodes (which occurred at ca 2655 Ma) post‐dates the majority of displacement along the Sunrise Shear Zone, but it remains uncertain if the ore in both structures formed simultaneously or separately. Overall, the Pb, Nd, Sr, C, O and S isotopic compositions of ore‐related minerals from both the Western Lodes and ore zones in the Sunrise Shear Zone are similar. Early low‐salinity aqueous‐carbonic fluids and late high‐salinity fluids with similar characteristics are trapped in inclusions in quartz veins from both the Sunrise Shear Zone and the Western Lodes. The early CO₂, CO₂–H₂O, and H₂O‐dominant inclusions are interpreted as being related to ore formation, and to have formed from a single low‐salinity aqueous‐carbonic fluid as a result of intermittent fluid immiscibility. Homogenisation temperatures indicate that these inclusions were trapped at approximately 280°C and at approximately 4 km depth, in the deeper epizonal range. Differences between the ore zones are detected in the trace‐element composition of gold samples, with gold from the Sunrise Shear Zone enriched in Ni, Pb, Sn, Te and Zn, and depleted in As, Bi, Cd, Cu and Sb, relative to gold from the Western Lodes. Although there are differences in gold composition between the Sunrise Shear Zone and Western Lodes, and hence the metal content of ore fluids may have varied slightly between the different ore zones, no other systematic fluid or solute differences are detected between the ore zones. Given the fact that the ore fluids in each zone have very similar bulk properties, the considerable differences in gold grade, sulfide mineral abundance, and ore textures between the two ore zones most likely result from different gold‐deposition mechanisms. The association of ore zones in the Sunrise Shear Zone with pyrite‐replaced BIF suggests that wall‐rock sulfidation was the most significant mechanism of gold precipitation, through the destabilisation of gold‐bisulfide complexes. The Western Lodes, however, do not exhibit any host‐rock preference and multistage veins commonly contain coarse‐grained gold. Fluid‐inclusion characteristics and breccia textures in veins in the Western Lodes suggest that rapid pressure changes, brought about by intermittent release of overpressured fluids and concomitant phase separation, are likely to have caused the destabilisation of gold‐thiocomplexes, leading to formation of higher‐grade gold ore zones.     

安徽铜陵地区成矿物质和含矿流体来源问题的探讨

本文运用宏观和微观、地质和地球化学相结合的方法，通过野外观察和岩矿石中微量元素、稀土元素、同位素及流体包裹体的分析，探讨了铜陵地区成矿物质和含矿流体的来源及性质。研究表明，铜金等金属有岩浆和地层两个来源，但以前者为主；硫的来源有三：即地层、岩浆热液和地下水热液；含矿流体来源早期以岩浆为主，晚期有地层水的加入。     

山东大庄子金矿微量元素特征及深部成矿远景

大庄子金矿床位于胶莱盆地与胶北地体接触带的北缘,有含金蚀变岩和含金石英脉2种矿石类型。对大庄子金矿微量元素特征的系统研究表明：大庄子金矿成矿过程主要处于中低温阶段,与Au元素关系最密切的是代表中温成矿阶段的Pb,Zn,Ag,Cu元素,以及代表低温成矿阶段的Hg元素,Au元素与低温微量元素的相关性大于与高温微量元素的相关性;大庄子金矿形成后遭受剥蚀作用不是很强,目前所开采部位主要是整个矿体的上部,其深部还有可供开采的资源量。