胡安·德富卡洋中脊富锌烟囱体流体通道演化特征

对采自Faulty Towers(47°57.447'N,129°6.568'W)硫化物烟囱群一个不再活动的烟囱体硫化物开展了详细的矿物学和地球化学研究。样品从外壁往内壁方向可划分为4个矿物组合带,分别为重晶石-无定形硅-铁氧羟化物带;白铁矿-黄铁矿-无定形硅-重晶石带;白铁矿-黄铁矿-闪锌矿-纤锌矿带;纤锌矿-黄铜矿-白铁矿带。从底部到顶部,样品通道形态主要有3种:不规则、不连续的多通道;椭圆形单通道;封闭的通道。矿物学研究证实,烟囱体以低温矿物组合白铁矿、纤锌矿为主,高温矿物黄铜矿少见,仅局限分布在流体通道附近。210Pb定年结果表明,烟囱壁形成经历较短时间(约3 a),而通道的闭合则经历了相对长的过程(约17 a)。结合矿物学研究,最终恢复了整个尖塔结构的生长历史。

The evolution characteristics of fluid conduits, a zinc-rich-spire struture from juan de fuca ridge

Mineralogical and geochemical studies have been carried out on an intact spire structure from Faulty Towers sulfide clusters. A sample displays four mineralogical zones from the exterior to the interior, i.e., a Fe-oxyhydroxide-barite-silica zone, a marcasite-pyrite-barite-silica zone, a marcasite-pyrite-sphalerite-wurzite zone, and a wurzite-chalcopyrite-marcasite zone, respectively. From the bottom to the top, there are three types of fluid conduits : irregular and discontinue multi-channels; oval-shape channel; and clogged channel. Mineralogy and mineral chemistry indicate low-teperature marcasite and wurtzite are the prominent mineral assemblage ,with minor chalcopyrite, only precipitated near the fluid conduits. Pb-210 data reflect that the walls formed in relatively short time (3 a), while the clogging of the fluid couduits goes through much longer time (17 a). Combined with microscopic study, the growth history of spire structure is recovered eventually.