PGE fractionation in seafloor hydrothermal systems: examples from mafic- and ultramafic-hosted hydrothermal fields at the slow-spreading Mid-Atlantic Ridge     

Jan Pašava  Anna Vymazalová  Sven Petersen 《Mineralium Deposita》2007,42(4):423-431

The distribution of platinum group elements (PGEs) in massive sulfides and hematite–magnetite±pyrite assemblages from the recently discovered basalt-hosted Turtle Pits hydrothermal field and in massive sulfides from the ultramafic-hosted Logatchev vent field both on the Mid-Atlantic Ridge was studied and compared to that from selected ancient volcanic-hosted massive sulfide (VHMS) deposits. Cu-rich samples from black smoker chimneys of both vent fields are enriched in Pd and Rh (Pd up to 227 ppb and Rh up to 149 ppb) when compared to hematite–magnetite-rich samples from Turtle Pits (Pd up to 10 ppb, Rh up to 1.9 ppb). A significant positive correlation was established between Cu and Rh in sulfide samples from Turtle Pits. PGE chondrite-normalized patterns (with a positive Rh anomaly and Pd and Au enrichment), Pd/Pt and Pd/Au ratios close to global MORB, and high values of Pd/Ir and Pt/Ir ratios indicate mafic source rock and seawater involvement in the hydrothermal system at Turtle Pits. Similarly shaped PGE chondrite-normalized patterns and high values of Pd/Pt and Pd/Ir ratios in Cu-rich sulfides at Logatchev likely reflect a similar mechanism of PGE enrichment but with involvement of ultramafic source rocks.  相似文献   

Distribution of platinum-group elements in the Platreef at Overysel,northern Bushveld Complex: a combined PGM and LA-ICP-MS study   总被引：1，自引：0，他引：1  

D. A. Holwell  I. McDonald 《Contributions to Mineralogy and Petrology》2007,154(2):171-190

Detailed mineralogical and laser ablation-inductively coupled plasma-mass spectrometry studies have revealed the physical manifestation of the platinum-group elements (PGE) within the Platreef at Overysel, northern Bushveld Complex, South Africa. The PGE in the Platreef were originally concentrated in an immiscible sulfide liquid along with semi-metals such as Bi and Te. As the sulfide liquid began to crystallize, virtually all the Os, Ir, Ru and Rh partitioned into monosulfide solid solution (mss), which on further cooling, exsolved to form pyrrhotite and pentlandite with Os, Ir and Ru remaining in solid solution in both phases with Rh prefentially partitioning into pentlandite. Platinum, some Pd and Au were concentrated in the residual sulfide liquid after mss crystallization, and were then concentrated in an immiscible late stage melt along with semi metals, which was expelled to the grain boundaries during crystallization of intermediate solid solution (iss) to form Pt and Pd tellurides and electrum around the margins of the sulfide grains. Tiny droplets of this melt trapped in the crystallizing mss and iss cooled to form Pt–Bi–Te microinclusions in all sulfide phases, whilst the excess Pd was accommodated in solid solution in pentlandite. Minor redistribution and recrystallization by hydrothermal fluids occurred around xenoliths and at the very base of the mineralized zone within the footwall, however, the overall lack of secondary alteration coupled with the volatile-poor nature of the gneissic footwall have allowed the preservation of what may be the most ‘primary’ style of Platreef mineralization. The lack of PGM inclusions within early liquidus phases suggests very early sulfur saturation in the Platreef, lending support to theories involving S saturation occurring prior to intrusion of the Platreef, possibly within a staging chamber.  相似文献   

粘土矿物在过去环境变化研究中的应用   总被引：9，自引：4，他引：9       下载免费PDF全文

隆浩  王晨华  刘勇平  马海州 《盐湖研究》2007,15(2):21-25,29

粘土矿物是一种广泛分布于地表的沉积物,其组合及含量的变化记录了源区过去气候环境变化的信息。因此,可以根据粘土矿物的含量和组合变化等信息推知其形成时期的气候环境,重建古环境,揭示气候环境演变的规律。粘土矿物是一种研究古环境演化重要的代用指标,在过去气候环境变化研究中有广阔的应用前景。  相似文献   

Late Quaternary clay minerals off Middle Vietnam in the western South China Sea: Implications for source analysis and East Asian monsoon evolution     

Christophe COLIN 《中国科学D辑(英文版)》2007,50(11):1674-1684

High-resolution clay mineral records combined with oxygen isotopic stratigraphy over the past 450 ka during late Quaternary from Core MD05-2901 off Middle Vietnam in the western South China Sea are re-ported to reconstruct a history of East Asian monsoon evolution. Variations in Illite, chlorite, and kaolinite contents indicate a strong glacial-interglacial cyclicity, while changes in smectite content present a higher frequency cyclicity. The provenance analysis indicates a mixture of individual clay minerals from various sources surrounding the South China Sea. Smectite derived mainly from the Sunda shelf and its major source area of the Indonesian islands. Illite and chlorite originated mainly from the Mekong and Red rivers. Kaolinite was provided mainly by the Pearl River. Spectral analysis of the kaolin-ite/(illite chlorite) ratio displays a strong eccentricity period of 100 ka, implying the ice sheet-forced win-ter monsoon evolution; whereas higher frequency changes in the smectite content show an ice sheet-forced obliquity period of 41 ka, and precession periods of 23 and 19 ka and a semi-precession period of 13 ka as well, implying the tropical-forced summer monsoon evolution. The winter monsoon evolution is generally in coherence with the glacial-interglacial cyclicity, with intensified winter monsoon winds during glacials and weakened winter monsoon winds during interglacials; whereas the summer monsoon evolution provides an almost linear response to the summer insolation of low latitude in the Northern Hemisphere, with strengthened summer monsoon during higher insolation and weakened summer monsoon during lower insolation. The result suggests that the high-latitude ice sheet and low-latitude tropical factor could drive the late Quaternary evolution of East Asian winter and summer monsoons, respectively, implying their diplex and self-contained forcing mechanism.  相似文献   

水体中硫化物测定方法探讨   总被引：1，自引：0，他引：1       下载免费PDF全文

刘洪林  于志强  吴启鲁  徐红蔚 《水科学进展》2002,13(2):211-214

通过对测定硫化物标准曲线的质量保证及不同污染程度水样的前处理方法的探讨,得出硫化物标准溶液需现用现配及针对污染程度不同的水样分别采取直接测定、抽滤测定和酸化-吹气法测定的结论.  相似文献   

利用非金属矿制备白炭黑现状及发展前景   总被引：8，自引：0，他引：8  

周光  王廷吉 《华东地质学院学报》2001,24(4):298-302

简术了白炭黑的用途和制备方法，综述了利用非金属矿制备白炭黑的方法和技术现状，对充分利用非金属矿制备白炭黑提供思路并展望其发展前景。  相似文献   

福建省尤溪峰岩铅锌银资源潜力及找矿方向探讨   总被引：4，自引：0，他引：4  

吴建设  黄仁生 《中国地质》2001,28(12):13-18

福建尤溪峰岩铅锌银矿床产于龙北溪组(Pt2-3l)绿片岩中,成矿构造环境为大陆古裂谷,矿床成因类型属块状硫化物矿床。通过一年多的资源调查评价(地质大调查项目)工作,地质找矿取得了重大进展,已控制的铅锌银资源量均达大型规模,预测该区具有寻找超大型矿床的潜力。该矿床的解剖对于福建北部、西部及相邻的浙江南部寻找同类型矿床具有指导意义。  相似文献   

硫化物矿物溶解度与溶液pH值的关系   总被引：2，自引：0，他引：2  

贾建业  兰斌明  谢先德  吴大清  汤艳杰  王燕  王建成 《吉林大学学报(地球科学版)》2001,31(3):241-246

硫化物作为自然界常见的一大类矿物 ,由于溶解度很小 ,硫化物对水pH值的影响以及水对它的溶解度影响往往被人们所忽视。通过计算常见硫化物矿物的自由能ΔG0f、溶度积Ksp和溶解度S、绘制logS—pH曲线 ,得出硫化物矿物在不同 pH值条件下的溶解规律 ,水溶液的pH值受硫化物矿物的控制 ;反过来 ,水溶液的pH值也影响着矿物溶解度的大小。此外 ,对硫化物矿物饱和溶液的缓冲范围、缓冲容量和硫化物与溶液pH值相互作用的机理进行了探讨  相似文献   

环境矿物材料基本性能：无机界矿物天然自净化功能   总被引：53，自引：23，他引：53       下载免费PDF全文

鲁安怀 《岩石矿物学杂志》2001,20(4):371-381

重点阐述环境矿物材料基本性能，包括矿物表面吸附、孔道过滤、结构调整、离子交换、化学活性、物理效应、纳米效应及与生物交互作用等，旨在发掘、凝炼并新提出物理方法和化学方法之后与有机界生物同效的无机界矿物天然自净化功能的基础理论与应用方法，以发展和完善无机矿物与有机生物所共同构筑的自然界中存在的天然自净化系统，并就目前笔者在黄铁矿、锰钾矿、金红石、蛭石、蒙脱石、苋铁铁钒等天然矿物方面已经完成和正在开展的一系列环境矿物材料研究工作进行了举例说明。  相似文献   

Petrochemical Investigation of the Antique Ophiolite (Philippines): Implications on Volcanogenic Massive Sulfide and Podiform Chromitite Deposits   总被引：5，自引：0，他引：5  

Rodolfo A. TAMAYO Jr    Graciano P. YUMUL Jr    René C. MAURY  Mireille POLVÉ  Joseph COTTEN  Marcel BOHN 《Resource Geology》2001,51(2):145-164

Abstract: The Antique ophiolite, located in Panay island (west‐central Philippines), corresponds to several tectonic slices within the suture zone between the Philippine Mobile Belt (PMB) and the North Palawan Block (NPB). It includes dismembered fragments of a basaltic sequence, dominantly pillow‐lavas with minor sheet flows, rare exposures of sheeted dikes, isotropic gabbros, subordinate layered mafic and ultramafic rock sequences and serpentinites. Most of the ophiolite units commonly occur as clasts and blocks within the serpentinites, which intrude the whole ophiolitic body, as well as, the basal conglomerate of the overlying Middle Miocene sedimentary formation. The volcanic rock sequence is characterized by chemical compositions ranging from transitional (T)‐MORB, normal (N)‐MORB and to chemistry intermediate between those of MORB and island arc basalt (IAB). The residual upper mantle sequence is harzburgitic and generally more depleted than the upper mantle underlying modern mid‐oceanic ridges. Calculations using whole‐rock and mineral compositions show that they can represent the residue of a fertile mantle source, which have undergone degrees of partial melting ranging from 9‐22.5 %. Some of the mantle samples display chondrite‐nor‐malized REE and extended multi‐element patterns suggesting enrichments in LREE, Rb, Sr and Zr, which are comparable to those found in fore‐arc peridotites from the Izu‐Bonin‐Mariana (IBM) arc system. The Antique ultramafic rocks also record relatively oxidizing mantle conditions (Δlog f_O2 (FMQ)=0.9‐3.5). As a whole, the ophiolite probably represents an agglomeration of oceanic ridge and fore‐arc crust fragments, which were juxtaposed during the Miocene collision of the PMB and the NPB. The intrusion of the serpentinites might be either coeval or subsequent to the accretion of the oceanic crust onto the fore‐arc. Volcanogenic massive sulfide (VMS) deposits occur either in or near the contact between the pillow basalts and the overlying sediments or interbedded with the sediments. The morphology of the deposits, type of metals, ore texture and the nature of the host rocks suggest that the formation of the VMS bodies was similar to the accumulation of metals around and in the subsurface of hydrothermal vents observed in modern mid‐oceanic ridge and back‐arc basin rift settings. The podiform chromitites occur as pods and subordinate layers within totally serpentinized dunite in the residual upper mantle sequence. No large coherent chromitite deposit was found since the host dunitic rocks often occur as blocks within the serpentinites. It is difficult to evaluate the original geodynamic setting of the mineralized bodies since the chemistry of the host rocks were considerably modified by alteration during their tectonic emplacement. A preliminary conclusion for Antique is that the VMS is apparently associated with a primitive tholeiitic intermediate MORB‐IAB volcanic suite, the chemistry of which is close to the calculated composition of the liquid that coexisted with the podiform chromitites.  相似文献