摘要
在东秦岭华北板块南缘祁雨沟金矿床中发现罕见的两颗粗粒自然金{110}自形晶体,产出于矿床晚期蚀变矿化阶段,出现在晶洞中,均可见10个发育完好的晶面。晶体是在溶解主成矿期自然金基础上的再生产物,是在中偏碱性热液溶解了已结晶的金,在天水加入后的酸性条件下,于方解石开始结晶后结晶生长的。共生矿物除石英、方解石等,并有多种Bi-硫盐和Bi,碲化物。在一定量碲的存在下,铋起着完好粗粒自然金成长的“催化剂”的作用。{110}自形晶金出现在富矿地段,系局部现象,也是指导矿床勘查及矿山开采的重要标志之一。
Two well—developed {110} euhedal gold crystals found in Qiyugou explosive-collapsed gold ore-deposit, occurred at the late stage of oremineralization and elnplaced in the drusy cavity. These two closely iregularly linked euhedra appeared ten well developed crystal faces respectively, the grain sizes of both euhedra were of 2mm. They were regenerated products which formed in response to the dissolution of the preexistent native golds developed at the main alteration-mineralization stages, and which went to crystalize merely after the addition of native water , in the mean time the weak-alkali hydro-thermal solution had changed into acidic, and then the calcite crystalized in advance. The associated minerals, except quartz, calcite and other gangue minerals, there were many varieties of Bi-sulfosalts and Bi-tellurides. It is suggested that in the presence of suitable quantity of tellurium, the bismuth play an important part in the growth of these euhedral gold crystals. Thc emergence of these euhedral crystals at the rich segment of ore body provided effective characteristic feature for both prospecting work and ming process.
