Measurement and research method of metallogenic depths of Jiaojia orefield and Linglong orefield Shandong Province, China

Taking the contribution of the tectonic force to the total hydrostatic pressure into account, the author puts forward a new method on the calculation of the depth of petrogenesis and metallogenesis which is summarized as follows: first the tectonic added hydrostatic pressured P_s is subtracted from the total hydrostatic pressure P, then using their difference P_r, according to the general method the depth of petrogenesis and metallogenesis can be determined in consideration of lateral constraint. By the new method the following data on the depths of the metallogenesis are obtained: 2 243.6 m (No. I and No. II veins with metallogenic epoch of 105 Ma) and 1 632. 38 m (No. III vein with 105 Ma) for Jiaojia orefield, and 3 454.97 m (NE-trending zone with 213.2 Ma), 1 902.79 III (ENE-trending zone with 100.28 Ma), 1 090.97 m (NE-trending zone with 80.67 Ma) and 720.55 m (NNE-trending zone with 71.86 Ma) for Linglong orefield. Project supported by the Foundation of the State Planning Commission, China and the Foundation of the State Science and Technology Commission, China.     

The color of pumice: case study on a trachytic fall deposit, Meidob volcanic field, Sudan

 This paper examines the cause of color variations of trachytic pumices which are essentially uniform in chemical composition and proposes a geological model for their formation. A pyroclastic sequence of distinct subunits with brown, buff, and black pumices was deposited during the 5000-B.P. eruption of a tuff ring in the central Meidob volcanic field (Sudan). Subunits of buff pumices locally contain minor amounts of streaky pumice with pale-gray and dark-gray domains. The combined evidence of petrographic studies, chemical analyses of whole pumices and groundmass separates, electron microprobe analyses, optical spectroscopy, transmission electron microscopy, and magnetic susceptibility measurements show that color variations of the pumice clasts are related to the size and distribution of Fe³⁺-rich oxide microcrysts. Buff pumice and light-gray domains of streaky pumice have a colorless, transparent groundmass with very few microcrysts. Dark-gray domains of streaky pumice contain abundant hematite and/or magnetite microcrysts visible in thin section within a transparent, colorless glass groundmass. The groundmass of the black pumice clasts is brown in thin section which is most likely caused by submicroscopic magnetite microcrysts. Brown pumice clasts have a mixed groundmass consisting of brown domains and domains with opaque microcrysts in transparent glass. Variations in the eruption dynamics have been inferred from lithological observations. Subunits of black pumices are related to eruption pulses with low magma discharge and high water/magma mass ratio, whereas subunits of buff pumice were deposited during eruption pulses with high magma discharge and low water/magma mass ratio. Brown pumices represent the top part of the magma body, and the initial stage of the eruption probably had a low magma discharge. Streaky pumices are interpreted as the product of syn-eruptive mixing of Fe³⁺-rich oxide microcryst-bearing magma and microcryst-free magma. Received: 3 February 1997 / Accepted: 28 July 1997     

广东莲花山斑岩型钨-金矿床蚀变矿化特征及分带模式

莲花山斑岩型钨－金矿床蚀变类型可以分作钾化、云英岩化、绢云母化、绿泥石化和青盘岩化。矿化表现为黑钨矿化、白钨矿－硫化物矿化、多金属硫化物矿化及黄铁矿化。蚀变在水平和垂向上具有分带性。由内向外由钾化向云英岩化、叠加蚀变带、绿泥石化＋绢云母化、青盘岩化转化。由浅向深，钾化增强，云英岩化减弱，被叠加蚀变带和绿泥石化及绢云母化所代替。矿化由内向外表现为由黑钨矿化向白钨矿化、多金属硫化物矿化、黄铁矿化转变，由浅向深由钨矿化转变为金矿化及多金属硫化物矿化。与典型斑岩型矿床蚀变分带对比，莲花山斑岩型矿床不同原岩类型蚀变特征变化较大，矿化则表现出富钨、金贫铜及钨金共同产出的特征。     

地质样品中微量金银的在线分离富集方法

提出用ＶＳ－Ⅱ型强碱性阴离子交换纤维定量富集、硫脲解脱，流动注射在线分离富集—火焰原子吸收光谱法测定地质样品中痕量金银的分析方法。该方法检出限低，金为１．４μｇ／ｍＬ，银为０．３５μｇ／ｍＬ，相对标准偏差均小于２％，采样频率为１２０次／ｈ，用于地质样品中痕量金银的直接测定，结果令人满意。     

我国最大古岩溶型铀矿床成因的同位素地球化学研究

据对某大型古岩溶型铀矿床中铀－铅同位素体系及硫、碳、氧、氢同位素组成的研究结果，表明该矿床成矿物质源自矿区众多地层，成矿流体的变质水和古岩溶水（古大气降水）的混合水；成矿经历了古岩溶铀淋积富集，燕山早、晚期构造运动促使两次含铀热水溶液改造、叠加成矿（１３５～１１９。６５Ｍａ），成矿作用与古岩溶和区域地质构造演化密切相关，属古岩溶型热造铀矿床。     

泌阳碱矿形成的地球化学模拟研究

泌阳碱矿过去一直被认为是原生沉积矿床。通过综合分析泌阳凹陷的地质、石油地质、碱矿地质和水文地质条件，从不同方面论证泌阳碱矿不太可能属于原生沉积矿床。利用地球化学模拟技术，从理论上模拟了泌阳碱矿的形成过程，提出了一种水－岩相互作用成矿模式，并用大量的事实支持了这种观点。     

金矿床地球化学异常模式研究的新进展

论述了近十年来金矿床地球化学异常模式研究的新进展，９０年代以前研究和建立了石英脉和蚀变岩型金矿地球化学异常模式，９０年代以来，研究和建立了中国主要类型金矿床地球化学导航异常模式，热液金矿床和原生叠加晕理想模式，金矿床包裹体气晕，离子晕及其叠加晕理想模式。     

马山金（硫）矿床地球物理地球化学找矿模式

根据矿床的地球物理地球化学异常特征，磁异常与金矿体的关系，地球化学异常及其垂向分带规律，归纳出矿床地球物理地球化学找矿模式和找矿标志。     

东风山前寒武纪含铁建造金矿床中的稀土元素

东风山含铁建造金矿床中稀土元素含量普遍较低。东风山群是含矿层,其不同层位岩石和矿物的稀土含量有所差别。大理岩和含铁层中铁闪石的稀土含量最低,甚至低于稀土地壳丰度;上部角岩、下部角岩和石榴子石中稀土含量近似其他壳丰度;而板岩和花岗岩中稀土含量远高于其他壳丰度。稀土元素分布的特点反映了东风山金矿床形成于一个半封闭和较还原的海盆地,金矿化是在弱碱性条件下产生。黄铁矿中出现独居石类矿物,这可能与陆壳重熔改造形成花岗岩时产生的局部富轻稀土热液沿黄铁矿裂隙渗入有关。     

蚀变岩中物质迁移的定量计算：以锡矿山锑矿床为例

本文提出了确定沉积岩蚀变作用过程中的不活动组分的方法，并以锡矿山锑矿床为例，定量计算了蚀变岩中各组分的带入带出量，研究表明：锡矿山锑矿硅化过程中ＴｉＯ２和Ａｌ２Ｏ３为不活动组；ＳｉＯ２，Ｋ２Ｏ，Ｎａ２Ｏ及锑，硫，坤，汞，铅和钡为带入组分；而ＣａＯ，ＭｇＯ，Ｆｅ２Ｏ３，ＭｎＯ及铜，锌为带出组分，锑，钡，硫，ＳｉＯ２和ＣａＯ有较大的带进或带出量，锡矿山锑矿床矿石矿物为单一辉锑矿可能是由于矿液中缺少其它