摘要
云南老王寨金矿与金矿化时空密切共生的煌斑岩可分为新鲜(弱蚀变)、蚀变和矿化3种。固定铵(NH_4^+)含量测定结果表明,新鲜煌斑岩固定铵含量明显高于其他幔源岩石、低于矿区碳质围岩的固定铵含量。笔者认为该特征可能不是地壳混染的结果,从新鲜煌斑岩→蚀变煌斑岩→矿化煌斑岩,固定铵含量递增,且与金含量具较好的正相关,表明矿区煌斑岩蚀变流体和矿化流体中均可能存在铵,铵在金矿化流体中对金的迁移起了作用。
The lamprophyres in Laowangzhai gold orefield, Yunnan Province, which are closely associated with gold mineralization both in space and in time, are mainly minettes with a major mineral assemblage of clinopyroxene, mica, K-feldspar; and occasionally kerantites with a major mineral assemblage of clinopyroxene, mica, plagio-clase. According to the intensity of alteration and mineralization, rocks can be divided into fresh (weakly altered), altered and mineralized ones. The determination of fix-ammonium (NH4+) contents shows that the NH4+ contents of fresh rocks in the orefield (minettes and kerantites are 74. 34 × 10-6 to 135. 94×10-6 and 119. 97× 10-6 to 468. 48× 10-6 respectively) is higher than that of other mantle-derived rocks (1×10-6 to 21 X 10-6) , but lower than that of carbonaceous rocks in the orefield (799. 60 × 10-6 to 1742. 46×10-6). The analyses of NH4+ occurrence show that lamprophyres are of the NH4+-rich rock type. Combining the Sr isotopic compositions and the results of binary mixing, this paper suggests that lamprophyres in the orefield with a high a fix-ammonium content may not be the producet of crustal contamination, but a result of metasomatism of the source mantle. From fresh → altered → mineralized, the NH4+ contents of lamprohyres in the orefield increase progressively (74. 34× 10-6 to 468. 48×10-6, 200. 80×10-6 to 836. 10× 10-6 and 614. 50× 10-6 to 1045. 94 × 10-6, respectively) , and show good linear relations between Au and Au/ NH4+. This feature shows that the mineralized fluids contain NH4+, and NH4+ may taken part in the migration of Au in the mineralized fluids.
出处
《地质论评》
CAS
CSCD
北大核心
2001年第1期27-33,共7页
Geological Review
