Important Geological Factors Controlling the Formation of Gold Deposits in East China

The major gold deposits in east China are characterized by their occurrence in pre-Cambrian host metamorphic rocks,restriction in some specific stratigraphic-structural terranes,tendentious localization in ductile or ductile-brittle shear zones,association with the syntexis type granitoids,and significant remobilization,superimposition and enrichment by the later stage Mesozoic tectono-magmatic activities.     

风化壳型稀土矿床中稀土元素的活化与迁移

稀土元素（REE）广泛应用于新能源、国防军工等高科技产业中,是一类战略性关键矿产资源。风化壳型稀土矿床是中国最具竞争优势的稀土资源,其供应了全球90%以上的重稀土。阐明这类稀土矿床的成矿机制,可为寻找和高效开采利用该类稀土资源提供理论支持。文章以稀土元素的活化和迁移这两个关键过程为切入点,总结近年来取得的最新研究成果,并对未来的研究方向提出展望。该类矿床主要发育于富稀土花岗岩类的风化壳中,其中稀土配分模式主要受基岩控制。花岗岩类风化壳的形成以化学风化和生物风化作用为主。长石、云母和角闪石等主要造岩矿物风化形成的黏土矿物和铁锰氧化物是该类矿床中离子态稀土的主要赋存载体。而离子态稀土则来源于基岩中易风化和中等抗风化（含）稀土副矿物的风化和分解。此外,微生物分泌的有机酸等代谢产物可以促进难风化的独居石和磷钇矿等副矿物的风化和分解,加速稀土元素活化−迁移。与此同时,微生物作用还会导致轻稀土和重稀土的显著分异,其中革兰氏阳性细菌对重稀土的选择性显著高于轻稀土。在风化淋积过程中,稀土元素的络合离子可能是风化壳中稀土迁移的主要形式,主要受pH值、次生矿物形成和络合环境影响。值得注意的是,除了F−和${mathrm{CO}}_3^{2-} $等无机配体,有机质也可以直接与稀土离子络合或螯合,充当有机配体促进稀土的运移。因此,风化壳型稀土矿床中稀土元素的活化和迁移机制主要受化学风化和生物风化过程控制,是无机和有机共同作用的结果,但其对该类矿床形成的贡献尚待定量评估。     

川西北地区微细粒浸染型金矿成矿的区域地质、地球物理、地球化学特征

总结了川西北金三角地区的区域地质和矿床地质特征，研究了区域重力场和金矿发育的关系，详细论述了本区金矿发育的区域地球化学背景、区化异常特征及东北寨金矿的地球化学特征。从地球化学方面进行了成矿预测，指明本区尚有较好的找矿前景，应进一步加强工作。     

块状硫化物矿石中硫化物的压溶和增生及成矿意义——以加拿大西部矿床为例

加拿大西部块状硫化物矿石普遍地发生过硫化物的压溶和增生。增生作用根据增生体的成分可以分为同质增生和异质增生,根据动力环境可以分为静态增生和动态增生。三晶嵌接结构可以是静态增生的产物。压溶和增生是块状硫化物矿床成岩和变质过程中的重要作用。脉石矿物的压溶可使原生矿石就地加富,硫化物的压溶可使成矿物质发生再活化。增生可促进矿质沉淀。富含硫化物的地层之所以能成为地球化学障而有利于后期热液叠加和层控矿床的形成,硫化物晶芽的增生是一种重要机制。     

辽宁树基沟铜锌矿成矿时代及矿石再活化机制

树基沟铜锌矿是产于太古宙绿岩带中的与火山岩有关的块状硫化物（VMS）矿床,运用LA-ICP-MS锆石U-Pb定年得到含矿围岩(黑云斜长片麻岩原岩)的结晶年龄约为2 565 Ma,近似代表树基沟矿体的形成时代。后期变质变形作用使矿石结构构造发生了巨大的变化,形成变质变形作用特有的结构构造,有变斑晶结构、硫化物生长结构、碎裂结构、旋转碎斑结构、充填和交代结构以及退变质结构等。成矿组分的两期再活化过程对应了两期变质变形事件：第一期变质变形过程中,矿石以机械再活化迁移为主,并在压力小的位置形成“铜矿囊”;第二期变质变形过程中,矿石的活化方式呈现出复合再活化的特点,具体表现为黄铁矿变斑晶颗粒被再活化的石英-硫化物细脉充填,并发育一定程度的交代作用。     

辽宁庄河木鱼房金矿的地质特征及成因探讨

通过对辽宁庄河木鱼房金矿的区域地质背景、矿体地质特征、围岩蚀变特征的详细研究,确定该金矿的物质来源于太古宙深成变质岩——得胜片麻杂岩.在区域岩浆热动力作用下,金元素活化转移,沿断裂构造充填,经过多期次的蚀变、充填、胶结,最后形成以石英脉为主体的含金石英脉型金矿.该矿床形成于晚三叠世,其成因类型为典型的热液蚀变型.     

A laboratory study of the biogeochemical cycling of Fe,Mn, Zn and Cu across the sediment-water interface of a productive lake

Laboratory incubation experiments were carried out on sediment cores collected from Esthwaite Water, U.K., during April 1987, when the sediments displayed a characteristic surface (1.5 to 2 cm) oxide floc. The experiments were undertaken at 10°C, in the dark, under variable redox and pH conditions for periods of ~ 720 h (30 d). In some cases, realistic amounts of decomposing lake algae were added to simulate the deposition of an algal bloom. Pore waters and overlying waters were obtained from the incubated sediment cores at various time intervals and the samples analysed for pH and dissolved Fe, Mn, Zn and Cu by AAS. The results demonstrated that trace metal concentrations at the sediment-water interface can show rapid, pulsed responses to episodic events associated with controlling factors such as algal deposition and mixing conditions. The variations in dissolved Fe and Mn concentrations could generally be explained by their well known redox behaviour. Appreciable loss of Mn from solution under conditions of well-developed anoxia was consistent with adsorption of Mn²⁺ by FeS. Cu and Zn were both rapidly (24 h) released into solution during incubation of sediment cores prior to the development of anoxia in the overlying waters. Their most likely sources were the reductive remobilization of Mn oxides and the decomposition of organic matter. The addition of decomposing algae to a series of cores resulted in even higher interfacial dissolved concentrations of Cu and Zn, probably through acting as a supplementary source of the metals and through increased oxide dissolution. Switching from anoxic to oxic conditions also rapidly increased dissolved Cu and Zn concentrations, possibly due to their release during the oxidation of metal sulphides. The enhanced releases of dissolved Cu and Zn were generally short-lived with removal being attributed to the formation of sulphides during anoxia and to adsorption by Fe and Mn oxides under oxic conditions.