挪威某些铜镍矿石中单斜磁黄铁矿出溶体的退火和粗化   总被引：4，自引：0，他引：4  

顾连兴 Vokes  FM 《矿物学报》1997,17(1):17-23

在挪威某些正岩浆铜镍矿床的矿石中，六万磁黄铁矿基质内的单斜磁黄铁矿叶片是高温时形成的磁黄铁矿固溶体在降温过程中出溶的产物。出溶叶片宽度和间距的加大、叶片的带状分布、楔形尖端、箱状扭曲和复杂叶片等结构，表明出溶产物在不高于单斜-六方转变温度（254℃）的条件下发生过显著的退火和粗化。重结晶的六方磁黄铁矿基质中所保存的单斜变种甚少，表明变质作用所引起的矿石重结晶，可使磁黄铁矿吸收其中的单斜出溶体而发生均匀化。  相似文献   

Biogeochemical Prospecting of Sulphide Minerals in Winder Valley, Balochistan, Pakistan   总被引：1，自引：0，他引：1  

Shahid NASEEM  Shamim Ahmed SHEIKH 《Resource Geology》2002,52(1):59-66

Abstract: The Mor Range is mountainous terrain in southern Balochistan dominantly occupied by exposures of rocks of the Ferozabad Group which is comprised of Lower‐Middle Jurassic carbonates and siliciclastics. This group contains syngenetic and epigenetic Zn–Pb–Ba mineralization classified as Stratiform Sediment‐Hosted (SSH) and Mississippi Valley Type (MVT) deposits. Three important flora of the Saharo–Sindian, phytogeographical region of Pakistan, namely Tamarix aphyl–la, Salvadora oleoides and Acacia arabica have been studied as a mineralization prospecting tool. Samples of these species were collected from Winder Valley adjoining the Mor Range to prospect for new areas of mineralization, besides the known sulphide deposits. This study revealed the Draber, Thorar, Raj, Mithi and Kanrach localities as new prospect. Quantitative estimation of biophile elements (Zn–Cu–Pb) from the three species was made. A number of new Zn, Cu and Pb anomalies were distinguished in the area. The variation in the constituents of these species from different localities possibly varies with nature and distance from bedrock, mobility, climate, average abundance in the plant ash and exclusion mechanism of the flora. Acacia arabica with deep penetrating roots shows the best results and could be used to delineate new horizons of mineralization. In these species Zn and Cu are relatively concentrated whereas Pb shows limited enrichment. Lead therefore is the element best suited for pinpointing the mineralization owing to its relatively less mobile character. Relationships among Zn–Cu–Pb have been established using scattergrams and triangular variation diagram, which also demonstrate their genetic affiliation. Statistical analyses, such as determination of mean, mode, median, standard deviation, and coefficient of correlation, were also made to improve the raw geochemical data. These biogeochemical methods appear to be suitable in arid climate of Balochistan, if proper attention is paid to species selection.  相似文献   

Controls of dimethyl sulphide in the Bay of Bengal during BOBMEX-Pilot cruise 1998   总被引：1，自引：0，他引：1  

D. M. Shenoy  M. Dileep Kumar  V. V. S. S. Sarma 《Journal of Earth System Science》2000,109(2):279-283

The air-sea exchange is one of the main mechanisms maintaining the abundances of trace gases in the atmosphere. Some of these, such as carbon dioxide and dimethyl sulphide (DMS), will have a bearing on the atmospheric heat budget. While the former facilitates the trapping of radiation (greenhouse effect) the latter works in the opposite direction through reflectance of radiation back into space by sulphate aerosols that form from oxidation of DMS in atmosphere. Here we report on the first measurements made on DMS in the Bay of Bengal and the factors regulating its abundance in seawater. Phytoplankton alone does not seem to control the extent of DMS concentrations. We find that changes in salinity could effectively regulate the extent of DMSP production by marine phytoplankton. In addition, we provide the first ever evidence to the occurrence of DMS precursor, DMSP, in marine aerosols collected in the boundary layer. This suggests that the marine aerosol transport of DMSP will supplement DMS gaseous evasion in maintaining the atmospheric non-sea salt sulphur budget.  相似文献   

Facies architecture of a silicic intrusion-dominated volcanic centre at Highway–Reward, Queensland, Australia     

M. G. Doyle  J. McPhie 《Journal of Volcanology and Geothermal Research》2000,99(1-4)

The Highway–Reward massive sulphide deposit is hosted by a silicic volcanic succession in the Cambro-Ordovician Seventy Mile Range Group, northeastern Australia. Three principal lithofacies associations have been identified in the host succession: the volcanogenic sedimentary facies association, the primary volcanic facies association and the resedimented syn-eruptive facies association. The volcanogenic sedimentary facies association comprises volcanic and non-volcanic siltstone and sandstone turbidites that indicate submarine settings below storm wave base. Lithofacies of the primary volcanic facies association include coherent rhyolite, rhyodacite and dacite, and associated non-stratified breccia facies (autoclastic breccia and peperite). The resedimented volcaniclastic facies association contains clasts that were initially formed and deposited by volcanic processes, but then redeposited by mass-flow processes. Resedimentation was more or less syn-eruptive so that the deposits are essentially monomictic and clast shapes are unmodified. This facies association includes monomictic rhyolitic to dacitic breccia (resedimented autoclastic facies), siltstone-matrix rhyolitic to dacitic breccia (resedimented intrusive hyaloclastite or resedimented peperite) and graded lithic-crystal-pumice breccia and sandstone (pumiceous and crystal-rich turbidites). The graded lithic-crystal-pumice breccia and sandstone facies is the submarine record of a volcanic centre(s) that is not preserved or is located outside the study area. Pumice, shards, and crystals are pyroclasts that reflect the importance of explosive magmatic and/or phreatomagmatic eruptions and suggest that the source vents were in shallow water or subaerial settings.The lithofacies associations at Highway–Reward collectively define a submarine, shallow-intrusion-dominated volcanic centre. Contact relationships and phenocryst populations indicate the presence of more than 13 distinct porphyritic units with a collective volume of 0.5 km³. Single porphyritic units vary from <10 to 350 m in thickness and some are less than 200 m in diameter. Ten of the porphyritic units studied in the immediate host sequence to the Highway–Reward deposit are entirely intrusive. Two of the units lack features diagnostic of their emplacement mechanism and could be either lavas and intrusions. Direct evidence for eruption at the seafloor is limited to a single partly extrusive cryptodome. However, distinctive units of resedimented autoclastic breccia indicate the presence nearby of additional lavas and domes.The size and shape of the lavas and intrusions reflect a restricted supply of magma during eruption/intrusion, the style of emplacement, and the subaqueous emplacement environment. Due to rapid quenching and mixing with unconsolidated clastic facies, the sills and cryptodomes did not spread far from their conduits. The shape and distribution of the lavas and intrusions were further influenced by the positions of previously or concurrently emplaced units. Magma preferentially invaded the sediment, avoiding the older units or conforming to their margins. Large intrusions and their dewatered envelope may have formed a barrier to the lateral progression and ascent of subsequent batches of magma.  相似文献   

Metallogenic characteristics of the Wushan intrusive massive sulphide deposit, Jiangxi Province     

Meng Liangyi 《中国科学D辑(英文版)》1998,41(3):319-324

The metallogenic characteristics of the Wushan deposit are discussed based on its regional geology, mine geology, mineralization temperature and stable isotopic compositions. The deposit is closely related to granodiorite both spatially and genetically, thus belonging to intrusive massive sulphidr deposits, which art. different in metallogenic features from that of the volcanogenic massive sulphidr deposits.  相似文献   

辉锑锡铅矿的穆斯堡尔谱及其晶体化学研究     

黄文英 《矿物学报》1987,(4)

辉锑锡铅矿是结构复杂而尚未确定,以及晶体化学尚有争议的一种稀有矿物。X射线衍射结果表明其结构是由假四方亚层(称T层)和假六方亚层(称H层)穿插组成的层状结构。T层的化学成分具有MeS形式,H层则具有MeS_2形式。本文通过广西大厂的辉锑锡铅矿的穆斯堡尔谱研究,确定了矿物中Sn的大部分为Sn~(4+),而Sn~(2+)只占较少的部分;Fe中含有Fe~(3+)和Fe~(3+)。它们在T层和H层中的分布为Sn~(2+)(T)占5.6%,Sn~(4+)(T)占25.9%,Sn~(4+)(H)占68.5%,Fe~(2+)(T)占59.5%,Fe~(3+)(H)占40.5%。从Sn、Fe的穆斯堡尔谱参数还可看出H层的共价性比T层的强。  相似文献   

Sulphur cycling in organic-rich marine sediments from a Scottish fjord   总被引：1，自引：0，他引：1  

SIMON H. BOTTRELL  ROBERT J.G. MORTIMER  IAN M. DAVIES†  S. MARTYN HARVEY‡  MICHAEL D. KROM 《Sedimentology》2009,56(4):1159-1173

In this study, the biogeochemical transformations of sulphur in organic‐rich marine sediments in a Scottish fjord are investigated by a combination of pore water and sediment geochemistry with sulphide diffusive gradient thin‐film probes and sulphate isotopic data (δ³⁴S and δ¹⁸O). Particular attention is paid to sulphur cycling in the upper sediment profile where sulphate reduction occurs but free sulphide is below the detection limits of conventional pore water geochemical analysis but quantifiable by sulphide diffusive gradient thin film. In the uppermost part of the sediment core, δ¹⁸O sulphate decreased from near‐sea water values to +7‰, indicating that anoxic sulphide oxidation dominated during this interval. Sulphate δ³⁴S remained unchanged as there was no net sulphate reduction (i.e. reduction was balanced by re‐oxidation). Below 4 cm depth, there was a slight increase in sulphate δ³⁴S from 20‰ to 23‰ associated with minor accumulation of iron sulphide. The δ¹⁸O of the sulphate also increased, to around +10‰ at 10 cm depth, as a result of the isotopic exchange of sulphate–oxygen with pore water and/or sulphur disproportionation reactions mediated during sulphur cycling. These processes continued to increase the δ¹⁸O of the sulphate to 14‰ at 20 cm depth with no further change in the δ³⁴S of the sulphate. Below 20 cm depth, free sulphide is detectable in pore waters and both the δ³⁴S of the sulphate and sulphide increase with depth with an offset controlled by kinetic fractionation during bacterial sulphate reduction. The δ³⁴S of the sedimentary organic fraction shifted towards lower, more bacteriogenic, values with depth in the profile, without any increase in the size of this sulphur pool. Thus, the organic sulphur fraction was open to interaction with bacteriogenic sulphide without the occurrence of net addition. Therefore, caution should be exercised when using sulphur isotopic compositions to infer simple net addition of bacteriogenic sulphide to the organic sulphur fraction.  相似文献   

Ore Group Classification - A Case Study from Ingaldhal Sulphide Deposit, Karnataka Craton, India     

Joju P. Antony   《Gondwana Research》1999,2(1):67

All varieties of base metal sulphide deposits may be classified using base metal ratios viz. Copper Ratio (CR=100Cu/{Cu+Zn}), Zinc Ratio (ZR=100Zn/{Zn+Pb}) and Lead Ratio (PR=100Pb/{Pb+Cu}). Based on this ore group classification an attempt has been made to identify ore groups present in the late Archaean volcanic associated Ingaldhal Sulphide Deposit (ISD) of Karnataka Craton. Using base metal ratios (CR, ZR and PR) five distinct fields are suggested: Cu, Cu-Zn, Cu-Zn-Pb, Zn-Cu and Zn-Cu-Pb/Zn-Pb-Cu with their associated geological and geochemical characteristics. A transitional change in the ore groups is observed from the North Block (Cu rich groups; CR>50) to South Block (Zn and Pb dominated groups; CR<50) and the Main Block is represented by all the five ore groups.This classification may be useful as a pointer in the exploration of polymetallic base metal deposits. Copper rich groups (Cu, Cu-Zn and Cu-Zn-Pb) exhibit high concentration of Bi and Co, and low CaO and Cd whereas the Zn rich groups (Zn-Cu and Zn-Cu-Pb/Zn-Pb-Cu) show high CaO and Cd, and low Bi and Co. The CR of most of the ore groups exhibit a sympathetic relation with Co and Ag. A preliminary attempt has been made for better understanding of ore group genesis of ISD by integrating ore group characteristics with deduced geothermometry.  相似文献   

High mortality of Zostera marina under high temperature regimes but minor effects of the invasive macroalgae Gracilaria vermiculophylla     

H. Höffle  M.S. Thomsen  M. Holmer 《Estuarine, Coastal and Shelf Science》2011

The present study tested for density-dependent effects of the invasive drift macroalgae Gracilaria vermiculophylla (Ohmi) Papenfuss on growth and survival of the native eelgrass, Zostera marina L., under different temperature levels. Three weeks laboratory experiments were conducted in Odense, Denmark, combining three algae densities (control, low 1.9 kg WW m⁻², high 4.5 kg WW m⁻²) with typical Danish summer temperatures (18 °C) and elevated temperatures (21 °C and 27 °C). There was a significant effect of temperature on shoot survival with on average 68% mortality in the high temperature treatment but almost no mortality at the two lower temperatures. The higher mortality was probably caused by high sulphide levels in the sediment pore water (0.6 mmol l⁻¹ at 18 °C compared to 3.7 mmol l⁻¹ at 27 °C). Above-ground growth of the surviving shoots was also significantly affected by temperature, with leaf elongation rates being negatively affected, while the leaf plastochrone interval increased. Relative growth rate was significantly higher at 21 °C than at 18 °C or 27 °C, whereas rhizome elongation was significantly lowest at 27 °C. Elemental sulphur content in the plant tissues increased significantly with temperature and was up to 34 times higher (S⁰ in rhizomes) at 27 °C compared to the lower temperatures. In contrast to the temperature effects, cover by G. vermiculophylla did not cause significant effects on any seagrass responses. However, there was a (non-significant) negative effect of algal cover at the highest temperature, where the seagrass is already stressed. The latter results suggest that more studies should test for interaction effects between temperature and other anthropogenic stressors given that temperature is predicted to increase in the near future.  相似文献   

基体分离-电位滴定法测定高硫金属矿中的微量氯   总被引：2，自引：1，他引：1  

胡晓静  卢琪  姜莉  钟志光  仇薪越  聂东锐  王琦  张华一  曹凤梅 《岩矿测试》2010,29(1):80-82

使用碳酸钠-氧化锌混合碱焙烧样品,将硫化物矿中的低价硫转化为硫酸盐或高价硫,过滤分离基体,采用电位滴定法测定硫化物矿(铜精矿、锌精矿、硫铁矿)中的微量氯,消除由于硫化银沉淀的产生对氯化银测定结果的干扰。通过电位突越,确定滴定终点,消除色度和浊度对滴定终点的影响。采用电极电位-浓度二次微商滴定曲线,计算滴定终点。对混合碱的选择及加入量、焙烧温度、溶液酸度、测定温度、滴定介质以及基体和共存元素的干扰进行了试验。方法精密度(RSD,n=9)均小于9%,回收率为94.1%~105.6%。  相似文献