含矿基性-超基性岩的镁铁比值          下载免费PDF全文

代俊峰  宫磊  霍永豪 《地质找矿论丛》2016,31(1):42-46

基性-超基性岩中赋存有铜镍硫化物矿床、豆荚状铬铁矿床等许多重要的矿床,基性-超基性岩成岩成矿方面的研究多采用镁铁比值,但以往利用该比值时未考虑岩石的SiO_2含量、地质构造及岩石蚀变等一些重要条件。文章结合国内外一些重要的铜镍矿床和铬铁矿矿床,考虑到上述的几个条件,讨论了镁铁比值在划分岩石类型方面的应用,通过计算给出了与前人不同的镁铁比值划分区间。  相似文献   

秘鲁马尔科纳铁矿区北部TA-02勘查区铜多金属矿地质特征及成矿类型          下载免费PDF全文

武晗 《地质找矿论丛》2022,37(4):490-500

秘鲁马尔科纳(Marcona)铁矿区北部TA-02勘查区蕴含丰富的铜矿和铁矿资源,并伴生锌、钴等矿产资源。TA-02勘查区处于环太平洋构造-岩浆活动带的东侧,西南部发育有圣尼古拉斯(San Nicolás)岩基,胡斯塔(Justa)断裂控制了区内的铁、铜矿化及阳起石化蚀变带,是勘查区内(铁)铜矿体的主要控矿构造;胡斯塔断裂内常充填磁铁矿体、铜矿体及不同种类的脉岩,矿体形态以脉状为主;矿石中含铜矿物主要为黄铜矿,伴生/共生金属矿物主要为磁铁矿、赤铁矿、钴矿物、闪锌矿等,铜矿化与铁矿化具有高度的一致性,共/伴生关系密切,二者呈正相关关系,因此铜矿区呈现较高的磁异常;此外,矿体穿切地层,赋矿围岩无专属性,围岩蚀变以阳起石化蚀变为特征。研究认为,TA-02勘查区铜多金属矿属于IOCG型(氧化铁型铜-金)矿床。  相似文献   

Petrological and Geochemical Constraints on the Protoliths of Serpentine‐Magnetite Ores in the Zhaoanzhuang Iron Deposit,Southern North China Craton     

MENG Jie  LI Houmin  LI Lixing  SANTOSH M.  SONG Zhe  YANG Xiuqing 《《地质学报》英文版》2018,92(2):627-665

The uncommon Mg-rich and Ti-poor Zhaoanzhuang serpentine-magnetite ores within Taihua Group of the North China Craton(NCC) remain unclear whether the protolith was sourced from ultramafic rocks or chemical sedimentary sequences. Here we present integrated petrographic and geochemical studies to characterize the protoliths and to gain insights on the ore-forming processes. Iron ores mainly contain low-Ti magnetite(TiO_2 ~0.1 wt%) and serpentine(Mg#=92.42–96.55), as well as residual olivine(Fo=89–90), orthopyroxene(En=89–90) and hornblende. Magnetite in the iron ores shows lower Al, Sc, Ti, Cr, Zn relative to that from ultramafic Fe-Ti-V iron ores, but similar to that from metamorphic chemical sedimentary iron deposit. In addition, interstitial minerals of dolomite, calcite, apatite and anhydrite are intergrown with magnetite and serpentine, revealing they were metamorphic, but not magmatic or late hydrothermal minerals. Wall rocks principally contain magnesian silicates of olivine(Fo=83–87), orthopyroxene(En=82–86), humite(Mg#=82–84) and hornblende [XMg=0.87–0.96]. Dolomite, apatite and anhydrite together with minor magnetite, thorianite(Th-rich oxide) and monazite(LREE-rich phosphate) are often seen as relicts or inclusions within magnesian silicates in the wall rocks, revealing that they were primary or earlier metamorphic minerals than magnesian silicates. And olivine exists as subhedral interstitial texture between hornblende, which shows later formation of olivine than hornblende and does not conform with sequence of magmatic crystallization. All these mineralogical features thus bias towards their metamorphic, rather than magmatic origin. The dominant chemical components of the iron ores are SiO_2(4.77–25.23 wt%), Fe_2O_3 T(32.9–80.39 wt%) and MgO(5.72–27.17 wt%) and uniformly, those of the wall rocks are also SiO_2(16.34–48.72 wt%), Mg O(16.71–33.97 wt%) and Fe_2O_3 T(6.98–30.92 wt%). The striking high Fe-Mg-Si contents reveal that protolith of the Zhaoanzhuang iron deposit was more likely to be chemical sedimentary rocks. The distinct high-Mg feature and presence of abundant anhydrite possibly indicate it primarily precipitated in a confined seawater basin under an evaporitic environment. Besides, higher contents of Al, Ti, P, Th, U, Pb, REE relative to other Precambrian iron-rich chemical precipitates(BIF) suggest some clastic terrestrial materials were probably input. As a result, we think the Zhaoanzhuang iron deposit had experienced the initial Fe-Mg-Si marine precipitation, followed by further Mg enrichment through marine evaporated process, subsequent high-grade metamorphism and late-stage hydrothermal fluid modification.  相似文献   

REE,Fe and Mn Contents of Calcites and Their Prospecting Signi¬ficance for the Banqi Carlin-type Gold Deposit in Southwestern ChinaEI北大核心CSCD     

Wang J.  Han Z.  Li C.  Gao Z.  Yang Y.  Zhou G. 《大地构造与成矿学》2018,(3):494-504

The Banqi gold deposit is one of the important Carlin-type gold deposits in the southwestern Guizhou Carlin-type gold district, and it is the first deposit of the type found in China. As the major gangue mineral in this deposit, calcite can be divided into four types based on their formation time: pre-mineralization, main metallogenic epoch, late stage of mineralization, and post-mineralization. All types of calcites have distinct features such as field occurrence, physical typomorphic characteristics and trace elements characteristics. The pre-mineralization calcites have the highest REE contents (∑REE=29.70-40.10 μg/g), which are characterized by the most enriched LREE (LREE/ HREE=1.96-3.03), a distinct positive Eu anomalies (δEu=3.83-5.02), and almost no Ce anomalies (δCe=1.02-1.05). The calcites of the main metallogenic epoch have relatively low REE contents (∑REE=10.76-15.53 μg/g), and are characterized by the most enriched HREE (LREE/HREE=0.11-0.23), almost no Eu (δEu=0.73-1.20) and Ce anomalies (δCe=0.88-1.25). The calcites of the late stage of mineralization have the lowest REE contents (∑REE=2.82-4.34 μg/g), and are characterized by enriched HREE (LREE/HREE=0.26-0.86), weakly negative Eu (δEu=0.67-0.83) and Ce anomalies (δCe=0.55-0.81), which are similar to those of the calcites of the main metallogenic epoch. The post-minera¬lization calcites have relatively low REE contents (∑REE=6.92-10.91 μg/g), characterized by enriched LREE (LREE/HREE=1.83-2.34), weakly negative Eu anomalies (δEu=0.72-0.74) and moderately negative Ce anomalies (δCe=0.41-0.50). In addition, the Fe and Mn contents of ore-forming stage calcites are obviously higher than that of the calcites unrelated to mineralization, and negatively correlated with LREE/HREE ratio, which illustrates that the HREE concentrations of calcites are controlled by the incorporation of Fe and Mn. Thus, it will provide an important exploration indicator for the Yunnan-Guizhou-Guangxi Carlin-type gold deposits through the study of typomorphic characteristics of calcite. © 2018, Science Press. All right reserved.  相似文献   

湖北金山店矽卡岩型铁矿田硫同位素特征及其地质意义   总被引：2，自引：1，他引：1  

朱乔乔  谢桂青 《岩石学报》2018,34(9):2518-2534

矿集区或矿田尺度硫同位素的空间分布特征研究不仅具有重要的理论意义,而且对找矿实践具有重要的指示作用。本文对金山店矿田范围内的矽卡岩型铁矿床开展了系统的硫同位素研究工作,发现该矿田内矽卡岩型铁矿床中的黄铁矿(+15. 1‰~+25. 6‰)、硬石膏(+24. 9‰~+31. 5‰)和石膏(+27. 5‰~+30. 4‰)均具有富集重硫同位素的特征,明显不同于岩浆热液矿床中这些矿物的δ~(34)S值组成特征,且硬石膏和石膏的δ~(34)S值与三叠系嘉陵江组地层中沉积石膏的δ34S值较为接近,暗示金山店矿田内矽卡岩型铁矿中的硫可能主要来自于含膏盐地层。含膏盐地层广泛参与了金山店矿田中矽卡岩型铁矿的成矿作用,对成矿作用产生了重要的影响:大量硫酸根(SO_4~(2-))的还原过程可以将成矿体系中的Fe~(2+)氧化成Fe~(3+),导致大量磁铁矿的形成;含膏盐地层与流体作用形成大量的盐溶角砾岩,有利于加速成矿流体与围岩之间的水岩作用,并提供容矿空间。系统的对比研究发现,大冶地区的矽卡岩型铁矿和矽卡岩型铁铜矿的赋矿地层、热液硬石膏/石膏规模和硫同位素值组成均存在明显的差异,暗示这些矿床的成矿围岩存在显著的差异。鄂东矿集区尺度的硫同位素等值线所揭示的空间变化规律具有重要的找矿指示作用:在天青石矿区(如狮子立山)或附近可能具有寻找大冶式矽卡岩型铁矿床或铁铜矿床的潜力,而在硬石膏/石膏发育的矽卡岩型铁矿区(如金山店铁矿田和程潮铁矿)或附近则具有寻找狮子立山式热液天青石矿床的潜力。  相似文献   

水温分层型水库铁、锰垂直分布特征   总被引：8，自引：2，他引：6       下载免费PDF全文

徐毓荣  徐钟际  徐玮  向申  封珩 《湖泊科学》1999,11(2):117-122

贵阳市主要饮用水源地阿哈水库系水温分层型季节性缺氧水库,由于沉积物含高浓度Ｆｅ,Ｍｎ至使库水受到污染,经多年测定不同季节２０ｍ深垂直水柱结果表明,Ｆｅ,Ｍｎ分布随着季节变化,水库水温分层而变化,呈现明显的垂直分布规律,高浓度Ｆｅ,Ｍｎ主要出现在水温分层期水库中,下层,与库底缺氧,ＰＨ下降沉积物浓度Ｆｅ,Ｍｎ释放造成的二次污染等密切相关,从而为自来水厂实施优化分层取水和污染控制提供了依据。  相似文献   

现代海底的成矿作用与矿产资源     

张立生 《四川地质学报》1999,(4)

迄今所发现的现代海底成矿作用主要分布在沿大西洋中脊、东太平洋海岭和西太平洋沟弧盆系的各热液田中。现代海底成矿作用形成了大量具有重大经济意义的矿产,它们主要是铁锰结核、富钴结壳、多金属硫化物和被称之为２１世纪能源的气体水合物。现代海底成矿作用及其所形成矿床的研究是矿床前研究的前沿课题,它对于矿床学的发展,揭示成矿作用的奥秘和海底资源的开发都具有重大意义。  相似文献   

Correlation of rhyolitic pyroclastic eruptive units from the Taupo volcanic zone by Fe–Ti oxide compositional data     

Phil Shane 《Bulletin of Volcanology》1998,60(3):224-238

Grain-specific analyses of Fe–Ti oxides and estimates of eruption temperature (T) and oxygen fugacity (fO₂) have been used to fingerprint rhyolitic fall and flow deposits that are important for tephrostratigraphic studies in and around the Taupo volcanic zone of North Island, New Zealand. The analysed Fe–Ti oxides commonly occur in the rims of orthopyroxene crystals and appear to reflect equilibrium immediately prior to eruption because of geochemical correlation with the co-existing glass phase. The composition of the spinel phase is particularly diagnostic of eruptive centre for post-65 ka events and can be used to distinguish many tephra beds from the same volcano. The 29 different units examined were erupted over a wide range in T (690–990°C) and Δ log fO₂ (–0.1 to 2.0). These parameters are closely related to the mafic mineral assemblage, with hydrous mineral-bearing units displaying higher fO₂. Such trends are superimposed on larger differences in fO₂ that are related to eruptive centre. At any given temperature, all post-65 ka Okataina centre tephra have higher fO₂ values than post-65 ka Taupo centre tephra. This provides a useful criterion for identifying the volcanic source. There are no temporal T and fO₂ trends in the tephra record; over intervals >20 ka, however, tephra sequences from Taupo centre form characteristic T-fO₂ buffer trends mirroring the glass chemistry. Individual eruptive events display uniform spinel and rhombohedral phase compositions and thus narrow ranges in T (± <20°C) and log fO₂ (± <0.5), allowing these features to identify individual magma batches. These criteria can help distinguish tephra deposits of similar bulk or glass composition that originated from the same volcano. Distal fall deposits record the same T-fO₂ conditions as the proximal ignimbrite and enable distal–proximal correlation. Lateral and vertical compositional and T-fO₂ variability displayed in large volume (>100 km³) ignimbrites, such as the Oruanui, Rotoiti and Ongatiti, is similar to that found in a single pumice clast and thus mainly reflects analytical error; however, thermal gradients of ca. 50°C may occur in some units. Received: 6 April 1998 / Accepted: 16 June 1998  相似文献   

Some Pertinent Features of Mo‐Mineralized Granitoids in the Circum‐Pacific Region     

Shunso Ishihara  Kezhang Qing 《Resource Geology》2014,64(4):367-378

Petrological characteristics of granitic rocks related to the world large molybdenum deposits are studied. The granitoids are evaluated by Fe₂O₃+TiO₂‐FeO+MnO‐MgO diagrams, and found to all plot to the magnetite‐series field. They are all high silica and high‐K series, but not A‐type, except for the Climax‐type porphyries and some others in the Colorado mineral belt. By‐product molybdenum contained in porphyry copper deposits, lower grade but huge tonnage, occurs with calc‐alkaline I‐type magnetite‐series granodiorite and monzogranite. Felsic intrusive rocks of the Climax mine are A‐type and are exceptionally high in trace elements such as F and Rb, which are generally enriched with W and Sn‐related granitoids that originated in crustal source rocks. The by‐product molybdenites in porphyry copper deposits appear to originate in adakitic granodiorite or monzogranite, having deep origins with the subducted slab or thickened juvenile mafic lower crust. Therefore, there is no single magma type but the magnetite series, which concentrates a large volume of molybdenum in the ore deposits.  相似文献   

Trace Element Geochemistry of Magnetite from the Fe(-Cu) Deposits in the Hami Region, Eastern Tianshan Orogenic Belt, NW China   总被引：5，自引：0，他引：5  

HUANG Xiaowen  QI Liang  MENG Yumiao 《《地质学报》英文版》2014,88(1):176-195

Laser ablation–inductively coupled plasma–mass spectrometry(LA–ICP–MS) was used to determine the trace element concentrations of magnetite from the Heifengshan, Shuangfengshan, and Shaquanzi Fe(–Cu) deposits in the Eastern Tianshan Orogenic Belt. The magnetite from these deposits typically contains detectable Mg, Al, Ti, V, Cr, Mn, Co, Ni, Zn and Ga. The trace element contents in magnetite generally vary less than one order of magnitude. The subtle variations of trace element concentrations within a magnetite grain and between the magnetite grains in the same sample probably indicate local inhomogeneity of ore–forming fluids. The variations of Co in magnetite between samples are probably due to the mineral proportion of magnetite and pyrite. Factor analysis has discriminated three types of magnetite: Ni–Mn–V–Ti(Factor 1), Mg–Al–Zn(Factor 2), and Ga– Co(Factor 3) magnetite. Magnetite from the Heifengshan and Shuangfengshan Fe deposits has similar normalized trace element spider patterns and cannot be discriminated according to these factors. However, magnetite from the Shaquanzi Fe–Cu deposit has affinity to Factor 2 with lower Mg and Al but higher Zn concentrations, indicating that the ore–forming fluids responsible for the Fe–Cu deposit are different from those for Fe deposits. Chemical composition of magnetite indicates that magnetite from these Fe(–Cu) deposits was formed by hydrothermal processes rather than magmatic differentiation. The formation of these Fe(–Cu) deposits may be related to felsic magmatism.  相似文献