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Analytical and experimental studies on partitioning of elements and diffusion kinetics in some sulfide minerals in ore deposits

矿床中某些硫化物矿物的元素分配和扩散动力学的分析和实验研究

基本信息

批准号：
14340157
负责人：
MIZUTA Toshio
金额：
$ 10.94万
依托单位：
Akita University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

High-performance ArF laser abration equipment for induced coupled plasma mass spectrometer (ICP-MS) were introduced in 1999 during this research period for analyses of covering various kinds of geological samples.1)First topics of this study is the mineralogy and textures of active Vienna Wood seafloor hydrothermal deposit, Manus Basin, Papua New Guinea. Three hydrothermal sites are distributed in the Manus Back-arc basin : Pacmanus, Desmos and Vienna Wood sites. The mineralogy and formation environments for the massive sulphide ores from the Vienna Wood hydrothermal site were examined in this study.The Vienna Wood hydrothermal site is hosted by MORB-type basalt in graben morphology. Three types of ore samples were collected from the Vienna Wood site : (1)top of 15m tall active chimneys (type IA), (2)small active chimneys 3 meters away from the big chimneys (type IB) and (3)dead chimneys sampled 20 meters away from the active chimney (type II). The type IA ores consist of massive anhyd … More rite with disseminated dendritic pyrite, sphalerite and chalcopyrite. Type IB ores consist of minor anhydrite, Fe-oxide, dendritic pyrite, subhedral pyrite, sphalerite and chalcopyrite. Type II ores are dominated by framboidal to idiomorphic pyrite, dendritic pyrite, subhedral pyrite, chalcopyrite and sphalerite with minor anhydrite and baryte.Bulk chemical composition of the Vienna Wood ores show high Zn (16.5-40.0 wt.%), Cu (1.0-2.0 wt.%) and Pb (0.01-1.7 wt.%) contents in type IB than type IA (Zn = 0.3-2 wt.%, Cu = <0.1 wt.%, Pb =< 0.01 wt.%) or type II (Zn = 10-17 wt.%, Cu = <1.0wt.%, Pb =<0.4 wt.%). The mineralogy and formation environment for the Vienna Wood site are quite different from actively forming pollymetallic sulphide deposits associated with felsic volcanic rocks in the Pacmanus and Desmos sites.2)Second target is the geochemical features of Cyprus-type ore deposits. The Ghuzayn Cu-Fe massive sulfide ore deposit is one of the typical Cyprus-type deposits hosted in Oman ophiolite which providing a uniqu opportunity to study geochemical conditions of paleo-oceanic crust. Vertical distribution of Cu, Zn, Co and Ni in sheeted-dike complex, altered pillow basalts and massive sulfide ores were examined to clarify the chemical mobility in oceanic crust because of hydrothermal circulation and precipitation of sulfide minerals.Cu and Co are deposited as chalcopyrite and trace element in pyrite from hydrothermal solution. Among some circulating elements, preferential fixation of Zn and N to chlorite in altered rocks is responsible to the reason that these metals are not precipitated into massive ores.3)Geochemical characteristics of sedimentary rocks of pre-and post-Kuroko mineralization, Akita, is the third topics. The Hokuroku Basin is the most famous Kuroko district for seafloor hydrothermal mineralization around 15 m.y.ago. To clarify the environmental changes of Middle Miocene age, trace elements in sedimentary rocks of pre-and post-Kuroko ages are analyzed by ICP-MS. Two Akita areas are chosen for the geochemical research on sedimentary rocks. First is the Wagaomono area located in the western flank of mountain range of NE Japanese Island-Arc. The Dainihon-Yoshino Kuroko deposit is distributed in the upper Nishikurosawa Formation of this region. Second is the Iwaki area located in "Akita Oil Field" of the coastal district of Japan Sea.(LA)-ICP-MS for 34 elements in the sedimentary rocks and O and C isotope spectrometry for carbonates are employed. Systematics of SiO2-Fe2O3 reveals that the Wagaomono mudstones are likely to be the sediments of the mixed sources between biogenic and acidic tuffs origin. Mn/U ratios from the Nishikurosawa to the Onnagawa stages decrease dramatically from 1,200 to 24. These compositional changes show that sedimentary environments change clearly from oxidation state to reducing condition. Chondrite-normalized REE patterns of sedimentary rocks from all analyzed specimens show clear Eu negative anomalies. These Eu anomalies of sedimentary rocks from the Nishikurosawa Stage are larger than those the Onnagawa Stage in Wagaomono area. Mn crusts of carbonate nodules in the Iwaki area show the distinctive negative anomalies of cerium. Those data could indicate that the sedimentary conditions and their diagenetic processes of the Onnagawa age are much reducing than those of the Nishikurosawa age, in spite of almost the same abundance of Fe and Mn concentration. It is obvious that geochemical information of minor elements in fine-grained sedimentary rocks by rapid LA-ICP-MS analysis is quite effective to discuss the sedimentary environments. Less

1999年引进了高性能ArF激光烧蚀设备，用于感应耦合等离子体质谱仪（ICP-MS），用于分析各种地质样品。1）本研究的第一个主题是巴布亚新几内亚马努斯盆地活动维也纳伍德海底热液存款的矿物学和结构。马努斯弧后盆地有三个热液点：帕克马努斯、德斯莫斯和维也纳伍德。本文对维也纳伍德热液区块状硫化物矿床的矿物学特征和形成环境进行了研究。从维也纳伍德矿点采集了三种类型的矿石样品：（1）15 m高的活动烟囱顶部（IA型），（2）距离大烟囱3 m的小活动烟囱（IB型）和（3）距离活动烟囱20 m的死烟囱（II型）。IA型矿石由块状无水物组成， ...更多信息含浸染状树枝状黄铁矿、闪锌矿和黄铜矿。IB型矿石由少量硬石膏、氧化铁、树枝状黄铁矿、半自形黄铁矿、闪锌矿和黄铜矿组成。第二类矿石主要为自形黄铁矿、树枝状黄铁矿、半自形黄铁矿、黄铜矿和闪锌矿，含少量硬石膏和重晶石。维也纳伍德矿石的整体化学成分显示高Zn（16.5-40.0 wt.%），铜（1.0-2.0重量%）和Pb（0.01-1.7重量%）IB型的含量高于IA型（Zn = 0.3-2重量%，Cu = <0.1重量%，Pb =< 0.01重量%）或II型（Zn = 10-17重量%，Cu = <1.0重量%，Pb =<0.4重量%）。维也纳伍德矿址的矿物学和形成环境与帕克马努斯和德莫斯矿址中与长英质火山岩有关的活跃形成的多金属硫化物矿床有很大不同。2）第二个目标是塞浦路斯型矿床的地球化学特征。古宰因铜铁块状硫化物存款是一个典型的塞浦路斯型矿床在阿曼蛇绿岩，提供了一个独特的机会，研究古海洋地壳的地球化学条件。通过对板状岩墙杂岩、蚀变枕状玄武岩和块状硫化物矿石中Cu、Zn、Co、Ni的垂向分布特征的研究，阐明了热液循环和硫化物矿物沉淀在洋壳中的化学活动性，Cu、Co在热液中以黄铜矿和微量元素黄铁矿的形式沉积。在某些循环元素中，Zn和N在蚀变岩中的优先固定是这些金属没有沉淀成块状硫化物的原因。3）秋田黑矿化前后沉积岩的地球化学特征是第三个课题。北六盆地是大约1500万年前海底热液成矿作用最著名的黑子地区。为了阐明中中新世环境的变化，利用ICP-MS分析了黑子时代前后沉积岩中的微量元素，并选取了两个秋田地区进行了沉积岩地球化学研究。首先是位于东北日本岛弧山脉西翼的和高莫诺地区。大仁本-吉野黑子存款分布在该地区的上西黑泽组。其次是位于日本海沿岸地区“秋田油田”的磐城市地区。采用（LA）-ICP-MS法测定了沉积岩中34种元素的含量，采用O、C同位素法测定了碳酸盐岩的含量。SiO_2-Fe_2O_3系统学研究表明，和告莫诺泥岩可能是生物成因和酸性凝灰岩成因的混合物。从Nishikurosawa到Onnagawa阶段的Mn/U比值从1，200急剧下降到24。这些组成变化表明沉积环境明显地由氧化态向还原态转变。所有样品的稀土元素球粒陨石标准化模式均显示出明显的Eu负异常。在Wagaomono地区，这些Eu异常在Nishikurosawa阶的沉积岩中比在Onnagawa阶的沉积岩中更大。岩城地区碳酸盐结核的锰结壳显示出明显的铈负异常。这些数据可能表明，Onnagawa时代的沉积条件和成岩过程大大减少比Nishikurosawa时代，尽管几乎相同的丰富的Fe和Mn的浓度。可见，利用LA-ICP-MS快速分析细粒沉积岩中微量元素的地球化学信息对探讨沉积环境是十分有效的。少