中国砂金矿床吨位-品位模型

矿床品位－吨位模型研究属于学科前沿领域,它是系统勘查理论的重要组成部分。依据“１９９７年全国矿产储量数据库”资料,对全国３９４个砂金矿床建立了地质模型、品位模型、吨位－品位联合模型,模型类型包括频率直方图、累积频率分布图;分别总结了砂金矿床品位及吨位分布的典型数学地质特征。     

缅甸铂族金属砂矿中的矿物种类

采用电子探针分析（ＥＰＭＡ），对缅甸铂族金属砂矿中的矿物种类进行了研究。物质组成研究查明：主要组合矿物是Ｐｔ、Ｉｒ、Ｏｓ、Ｒｕ的自然元素和金属互化物。主要矿物是自然铂矿、铁铂合金、钌铱锇矿、等轴锇铱矿和铱锇矿。次要及稀有矿物是铂族金属的硫化物、砷化物、包括（Ｒｈ、Ｐｄ、Ｐｔ）２Ａｓ和（Ｒｈ、Ｐｄ、Ｐｔ、Ｎｉ）２Ａｓ两种陌生矿物、锑化物，以及含铂族元素的Ｆｅ、Ｎｉ、Ｃｕ硫化物。     

鲁中南地区第四系河流砂金成矿特征的研究

本文研究了鲁中南地区河流砂金富集成矿特征及成矿时代.区内第四系出露时代齐全,成因类型繁多,岩性复杂.河流砂金矿层主要位于冲积或冲洪(洪冲)积物的底部,即古老变质岩系基岩面之上的含泥砂砾或砾砂等粗粒沉积物中.据资料和第四纪以来气候的冷暖变化,区内河流砂金的成矿时代可划分为中更新世(早期)、晚更新世(早期)和全新世(早、中期).     

台湾海峡西部表层沉积地球化学元素分布及砂矿成矿显示

本文研究了台湾海峡西部海底表层沉积物中的２０种微量元素分布特征，划分４种组合类型。Ｚｒ、Ｌａ、Ｙ、Ｎｂ、Ｔｉ元素高含量区具有海底锆、钛砂矿可能成矿的良好显示，为海底砂矿找矿提供地球化学依据。     

山门金银矿床重砂异常特征及找矿意义

本文通过对山门金银矿床自然重砂矿物的系统研究,揭示了山门金银矿床自然重砂异常的分布特征,优选出具有重要找矿指示作用的重砂矿物,并确定标型矿物组合,结合地质特征建立山门金银矿床的自然重砂找矿模式,为找矿预测提供重要依据。     

Occurrence and Emplacement of Chromite Ores in Sindhudurg District,Maharashtra, India

<正>In the present study,we present the occurrence and emplacement of chromite ore deposits from two abandoned mines(Kankavali[Janoli]and Wagda) in the Sindhudurg district of Maharashtra,India.These ores,that occurred as lenses and are associated with metamorphic and ultrabasic rocks,consist of octahedral grains of chromite,while clinochlore is present between the interstices of these grains.The Kankavali(Janoli) and Wagda ores revealed a dominance of Cr_2O_3 followed by FeO and variable proportions of A1_2O_3,MgO,and SiO_2.The former deposits have a slightly higher Cr_2O_3(average 52 wt%) and FeO(～18 wt%) than those from Wagda(Cr_2O_3～50 wt%,FeO～25 wt%).The similar Cr~# values(0.73 for Kankavali[Janoli],0.74 for Wagda) correspond to those reported for typical podiform-type chromite deposits.We suggest that the ores were emplaced as phacoliths in folded outcrops with a steep easterly dip and a northwest-southeast trend.We postulate the continuation of the fold structure from Janoli to Wagda(～4.5 km apart) and the probable (sporadic) occurrence of chromite along this stretch.The possibility of the contribution of chromite grains from these areas to the coastal placer deposits cannot be ruled out.     

对博山区夏庄一带新近纪白彦组的初步认识

通过野外地质调查、采样化验及区域地质资料对比研究,初步认定赋存在淄博凹陷南缘夏庄、五福峪、马家庄等地下古生代寒武-奥陶纪灰岩、白云岩岩溶负地形中的砾岩层,其综合地质特征符合山东省岩石地层新近纪白彦组的现在定义,砾岩含金而未见金刚石.该地层的发现弥补了该区原有区域地质资料的不足,有助于对该区地质构造发展史的研究,也为今后的找矿工作提供了有价值的线索.     

Offshore Occurrences of Heavy-Mineral Placers,Northwest Galicia,Spain

ABSTRACT

Results of offshore water-jet sediment sampling demonstrate the potential for interstadial placer deposits of industrial minerals in the shore-face to inner-shelf of Cape Ortegal, NW Spain. Placer deposition is interpreted to have occurred during glacial interstadials since the Last Glacial Maximum, and deposits sampled at 24 to 42 m. BSL were formed during the Younger Dryas, and subsequently preserved as a result of very rapid rising sea-levels. The sediments are almost entirely terrestrially derived with a particularly high heavy mineral content (Sp. Gr. >2.9), of more than 75% in all samples. Reworked garnet from earlier-sedimentary deposits constitutes an important fraction of the placer deposits identified but is generally absent in other sediments. Indications of the presence of +5 m-thick paleo-placer deposits with sections include:

• Placer garnet + spinel grades increase with depth in those sediments at 24 to 42 m BSL to the ocean-floor.

• The d50 of sediments with background grades decrease with depth while those of placer deposits do not display any significant trend.

• Garnets in non-mineralized sediments are almost entirely angular, whereas in placer enriched sediments they vary in form from well-rounded to angular. Some grains in the latter display surface morphologies typical of reworked sediment while none of the former do.

Sediments deposited during glacial interstadials at depths of up to 130 m BSL may represent important, undeveloped exploration targets for offshore placer deposits of industrial minerals. Industrial mineral exploration should extend the depths of investigations to those corresponding to major interstadial periods.     

中国东北寒区的风化壳与砂金矿床

大、小兴安岭北部寒区发育有3个砂金富集区.大量的找矿实践表明, 区内砂金矿床与内生成矿作用没有必然的联系, 砂金矿床与区域发育的风化壳有着密切的空间关系, 风化壳中的低温地球化学作用对区域砂金矿床的形成具有一定的控制作用.在砂金的形成过程中寒冻气候条件至关重要, 寒冷的气候条件有利于风化壳的保存, 同时, 冰冻条件下的水文地质条件及电化学作用也有利于金在其中的活化、迁移、富集和生长.