黄铁矿成因形态学

在1981—1986年野外工作的基础上,作者对胶东三县四个金矿床黄铁矿晶体形态进行了系统研究,对其中2495粒晶体进行了统计,对300粒晶体进行了测角,对60粒晶体进行了微形貌观察。根据以上实际工作及国内外有关资料提出了黄铁矿晶休常见单形出现频率的定量资料与晶体微形貌的特点,特别是{210}面上负条纹的特征与成因探讨。并讨论了黄铁矿晶体形态与分带性,与形成温度,与主、微量成分,与共生组合及与矿化等的关系。查明黄铁矿形态及其晶面微形貌的发育与硫逸度、温度、冷却速度等密切相关。在以上基础上提出了胶东四个金矿床中蚀变岩型金矿及石英脉型金矿两种成因类型黄铁矿形态特征上的五点差异。最后对黄铁矿研究方法要点进行了总结。

Morphogenesis of Pyrite

The pyrite crystals investigated are collected in 1981-1986 from 4 gold mines in 3 counties of the Jiaodong region in eastern Shandong province,namely the Ling-long and Xiadian gold mines of Zhaoyuan Co., Qixia gold mine of Qixia Co. and Sanshandao gold mine of Yexian Co., Out of them 2495 are taken into ac-co tint in statistics, 300 are taken to goniometric measurements and 60 are taken to observations of surface microtopography under SEM. After a short review of the former theories and observations concerning the frequency of appearance of single forms of pyrite crystals, their development in the above - mentioned gold mines is summarized as the following. (1){ 100 } , { 210 } , { 111 } are the most common single forms, the frequency of appearance of which is arranged here in decreasing order. (2)The ratio of frequency of appearance of { 100 } '. { 210 } '. { 100 } equals to 224 I 42.8 : 1 in single-form crystals and 3.3 T 2.9 : 1 in combinate - form crystals. (3)The ratio of total frequency of appearance of single forms in all the crystals is as the following : { 100 } : { hko } : { 111 } : { hk1} : { 211 } : { 221 } equals to 1156 : 716 : 201: 18: 2 : 1 in which { hko } represent { 210 } , { 310 } , {410 } , {510} , {610} , {810} , {830} , { 910 } , { 11, 1, 0 } etc., while { hkl } represent { 321 }, { 421 } , {10,6,5}, {18,24,25}, {34,14,25} etc.. (4) Except { 100} , { 210 } , { 111 } , all the other single forms appear only in combination forms. (5){ 110 } does not appear, but { hkl } are more common than usual. Furthermore, the relations between morphology and surface microtopography, morphology and chemical composition, morphology and paragenesis, morphology and temperature of formation, morphology and zoning both horizontal and vertical as well as morphology and ore mineralization are investigated with regard to { 100 } , {210} and {111} , the 3 principal single forms of pyrite. The resultis as the following. (1) {100} appears in general under low fs and high temperature gradient at relatively higher or lower temperatures(in our case 218 C or 320 C) giving rise to uniform growth layers spreading evenly over {100 } faces and occurring in country rocks or marginal parts and predominating in the upper or lower part of the ore body at earlier or later stages in connection with weak or no metallic mineralization. (2) {210} and {111} appear in general under high fs and low temperature gradient at median temperature (in our case 227 - 3011) , formed by the stepped edges of growth layers piled up on { 100 } faces and occurring in central part of the vein and predominating in the middle portion of the ore body at the intermediate or slightly later stage in' close connection with strong metallic mineralization.Rise of Ni content favours the formation of {210} while high. As content at low temperature in weak alkalic environment favours the formation of {111} . Therefore {111} appears also in still later stage in shallow zone alone or together with { 100 } in combination. (3) Coase striae on { 100 } faces are due to isolated growth layer islands formed at still lower fs and higher temperature gradient than that of the formation of uniform and continuous growth layers. Since the former have not yet united to form the latter, there won't be any chance in this case for { 210 } and { m } to develop as stepped faces by the piled-up edges of growth layers on {100} . (4) On the contrary, in case of fs being higher and both temperature and temperature gradient being lower than the condition of the formation of the uniform and continuous growth layers on {100 } faces, which is possible in later or the latest stage in their growth process, thin and uniform growth layers will be piled up on { 210 } faces instead of being on { 100 } faces. The character of { 100 } faces will then change from F - face to S - face and that of { 210 } faces will be vice versa. In such case negative striae will appear on {210} faces instead of positive striae with the former overlapping the latter as is shown b