南海台西南盆地自生管状黄铁矿矿物学特征及其对天然气水合物的示踪意义  

Mineralogy of authigenic tube pyrite from the Southwest Taiwan Basin of South China Sea and its tracing significance for gas hydrates

作　　者：张美[1] 孙晓明[2,3,4] 芦阳[1] 徐莉[2] 陆红锋[5] 

机构地区：[1]中山大学地球科学系,广东广州510275 [2]中山大学海洋学院,广东广州519275 [3]中山大学地球科学,广东广州510275 [4]广东省海洋资源与近岸工程重点实验室,广东广州510640 [5]国土资源部广州海洋地质调查局,广东广州510760

出　　处：《矿床地质》2011年第4期725-734,共10页Mineral Deposits

基　　金：“天然气水合物资源勘查与试采工程(1272工程)”国家专项(编号:GZH201100305-06-06);国际海底区域研究开发“十一五”项目(编号:DYXM-115-02-1-11);高等学校博士学科点专项科研基金(编号:20090171120019);中央高校基本科研业务费专项资金(编号:09lgpy09);中国科学院边缘海地质重点实验室开放研究基金课题(编号:MSGL08-01,MSGLCAS03-4)的联合资助

摘　　要：在南海台西南区GC10岩芯中发现了大量自生管状黄铁矿,它是海洋沉积物缺氧硫酸盐还原过程的主要产物。扫描电镜和高分辨率透射电镜测试结果显示,这些管状黄铁矿主要由草莓状黄铁矿组成,且在管内各圈层分布不均:内层主要是单个的大颗粒草莓状黄铁矿,直径为40μm左右;中间致密层为具外壳结构的草莓状黄铁矿,经后期压实作用后呈五角十二面体紧密堆积;外层是疏松的混有部分杂质的黄铁矿。高分辨率透射电镜观测显示,草莓状黄铁矿中存在面缺陷,在平行于黄铁矿的(001)面存在白铁矿层。草莓状黄铁矿中的黄铁矿与白铁矿是同质异构体,而且,白铁矿的(101)平行于黄铁矿的(001),白铁矿的[010]方向平行于黄铁矿的[100],这是黄铁矿与白铁矿之间最易相互生长的面。草莓状黄铁矿微晶的形态各异,包括有序规则排列的球粒、部分有序排列的五角十二面体、无序排列的球粒、截角立方体、不规则体及亚微晶颗粒等,说明草莓状黄铁矿是在微生物参与下,在由强还原到局部弱氧化的环境中形成的。这种微环境的变化正好是下部上溢的甲烷在管状通道内与硫酸盐发生反应的结果。A lots of authigenic tube pyrites were collected from sediments in core GC10 from Southwest Taiwan Basin,South China Sea,which constitute a major product of anoxic sulfate reduction in marine sediments.Observation under SEM and HRTEM shows that the tube pyrite consists of pyrite framboids with varied layers： The inner layer consists of single large-sized pyrite framboids,with a diameter of about 40 μm.The medium layer is packed with pyritohedron consisting of a framboidal core with an outer crust.And the outer layer is pyrite with some other minerals.HRTEM observation shows that the framboidal pyrite has plane defects.The SAED pattern reveals that the marcasite layers occur parallel to（001） layers of the pyrite.That means the single（101） layers of marcasite that disrupt the regular sequence of（002） layers in pyrite.The pyrite and marcasite in the framboidal pyrites are polymorph.The crystal stucture have a strict orientation relationship： the layer（101） and direction of the marscaite parallel the layer（001） and direction of pyrite.This is the least misfit plane between pyrite and marcasite.The framboids of microcrystals are spherical in the inner layer and irregular crystals in the outer layer,showing cubic,truncated cubic,pyritohedral and spherical pyrite microcrystals.All this means that the pyrite framboids were formed under anoxic to locally oxidizing conditions.The changes of the condition results from anaerobic oxidation of methane（AOM） performed by consortia of methanotrophic archaea and sulfate reducing bacteria.

关 键 词：矿物学 自生管状黄铁矿 草莓状黄铁矿 天然气水合物 台西南盆地 南海 

分 类 号：P618.13[天文地球—矿床学] P578.2[天文地球—地质学]