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1.
湘南地区云英岩化作用及云英岩体型矿床特征   总被引:5,自引:4,他引:5       下载免费PDF全文
介绍了湘南地区云英岩的产出类型以及云英岩体型钨锡多金属矿床和云英岩体型铀多金属矿床的矿床特征。  相似文献   

2.
Tin deposits in the form of cassiterite occur in precambrian zoned pegmatite bodies intrusive into Archean metabasic and metasedimentary rocks in Bastar, MP. The associated economic minerals include columbite-tantalite, lepidolite, beryl etc. As a major part of the area is covered by a thick overburden, termite mounds have been used as geochemical sampling medium in view of their significant potentiality in tropical areas with overburden, and also because of the low cost and ease of sampling. Though many elements have been used as pathfinders for tin, tin itself acts as the best indicator of its deposits. The present work has given encouraging results, and therefore can be applied for tin prospecting and possibly for heavy metals like Nb, Ta, W, etc., in this and other areas where termite mounds have a good spatial distribution.  相似文献   

3.
The areal distribution of stream sediment and source-rock heavy mineralogy was studied to determine the mineralogical relations between source and derived sediment in the Piney Creek drainage basin of Wyoming. Heavy-mineral distribution in the streams was characterized using factor analysis. The results of analyses show that for an actively degrading stream system, the heavy-mineral composition of stream sediment is controlled to a considerable extent by the composition of local sediment sources and by continuous addition of detritus from bank cutting. Only the most common minerals from upstream sources persist as statistically significant variables downstream. In some cases the heavy-mineral mineral composition of stream sediment can be controlled by comparatively few, or volumetrically rare source rocks, even though more abundant source rocks supply a wide range of heavy minerals. Specific drainage configurations such as lakes and proximity of streams to major sediment sources significantly modify sediment mineralogy immediately downstream.  相似文献   

4.
The most important tin mineralization in Thailand is associated with the Late Cretaceous to Middle Tertiary western Thai granite belt. A variety of deposit types are present, in particular pegmatite, vein and greisen styles of mineralization. A feature common to most of the deposits is that they are associated with granites that were emplaced into the Khang Krachan Group, which consists of poorly sorted, carbonaceous, pelitic metasediments. Most of the deposits contain low to moderately saline aqueous fluid inclusions and aqueous-carbonic inclusions with variable CH4/CO2 ratios. Low salinity aqueous inclusions represent trapped magmatic fluid in at least one case, the Nong Sua pegmatite, based on their occurrence as primary inclusions in magmatic garnet. Aqueous-carbonic inclusions are commonly secondary and neither the CO2 nor NaCl contents of these inclusions decrease in progressively younger inclusions, implying that they are not magmatic in origin. Reduced carbon is depleted in the metasediments adjacent to granites and the δD values greisen muscovites are variable, but are as low as −134 per mil, indicative of fluid interaction with organic (graphitic) material. This suggests that the aqueous-carbonic fluid inclusions represent fluids that were produced, at least in part, during contact metamorphism-metasomatism. By comparing the western Thai belt with other Sn-W provinces it is evident that there is a strong correlation between fluid composition and pressure in general. Low to moderately saline aqueous inclusions and aqueous-carbonic inclusions are characteristic of mineralization associated with relatively deep plutonic belts. Mineralized pegmatites are also typically of deeper plutonic belts, and pegmatite-hosted deposits may contain cassiterite that is magmatic (crystallized from granitic melt) or is orthomagmatic-hydrothermal (crystallized from aqueous or aqueous-carbonic fluids) in origin. The magmatic aqueous fluids (those that were exsolved from granitic melts) are interpreted to have had low salinities. As a consequence of the low salinities, tin is partitioned in favour of the melt on vapour saturation. Thus with a high enough degree of fractionation, the crystallization of a magmatic cassiterite (or different Sn phase such as wodginite) is inevitable. Because tin is not partitioned in favour of the vapour phase upon water saturation of the granitic melts, it is proposed that relatively deep vein and greisen systems tend to form by remobilization processes. In addition, many deeper greisen systems are hosted, in part, by carbonaceous pelitic metasediments and the reduced nature of the metasediments may play a key role in remobilizing tin. Sub-volcanic systems by contrast are characterized by high temperature-high salinity fluids. Owing to the high chlorinity, tin is strongly partitioned in favour of the vapour and cassiterite mineralization can form by of orthomagmatic-hydrothermal processes. Similar relationships between the depth of emplacement and fluid composition also appear to apply to other types of granite-hosted deposits, such as different types of molybdenum deposits. Received: 8 September 1997 / Accepted: 28 October 1997  相似文献   

5.
The composition of accessory minerals from granites of the second phase, quartz-muscovite (+fluorite), and quartz-muscovite-topaz greisens from the Primorsky rapakivi granite complex, West Baikal region, were studied using backscattered scanning electron microscopy. Ilmenite from granites contains inclusions of cassiterite, titanocolumbite, fergusonite-(Y), polycrase-(Y), and betafite. Allanite-(Ce), bastnaesite-(Ce), xenotime-(Y), Y- and Zr-thorite, zircon, and cyrtolite have been identified in granites. Greisens contain cassiterite, ferrocolumbite (Ta/Nb = 0.02−0.06), pyrochlore-group minerals, ilmenorutile, rutile, wolframite, polycrase-(Y), monazite-(Ce), fluocerite-(Ce), bastnaesite-(Ce), cerphosphorhuttonite, thorite, and other minerals. The ferrocolumbite + ilmenorutile assemblage is typical of quartz-muscovite greisen, whereas the rutile + ilmenorutile + wolframite + W-columbite assemblage is contained in the quartzmuscovite-topaz greisen as a result of an increase in Eh and decrease in pH and potassium activity of solution in the back zone. The compositions of Th- and REE-bearing minerals indicate the important role of phosphate and fluorine complexes in the transport of these elements.  相似文献   

6.
云南个旧锡多金属矿床处于滇东南锡矿带的西端,是全球最大的锡多金属矿床之一。锡石作为个旧锡矿床中最主要的矿石矿物,其矿物化学特征对矿床成因具有重要的指示意义。本文运用扫描电镜、电子探针等手段对个旧锡多金属矿床中6种不同类型矿石中的锡石进行了详细的内部结构和矿物化学特征研究,并对其可能的成因进行了探讨。扫描电镜研究结果发现,除层间氧化矿型锡石较破碎外,其余类型锡石内部均发育有明显的环带结构。电子探针分析结果显示:各类型矿石中锡石的SnO_2质量分数变化范围为97.700%~101.728%;Ta_2O_5、FeO、ZrO_2、HfO_2平均质量分数较高,指示锡石形成于高温热液环境;(Fe+Mn)/(Nb+Ta)显示个旧锡矿区各类型矿石中的锡石具有热液锡石的特征,且各类型锡石中Nb_2O_5和MnO的质量分数极低,说明成矿热液可能来自于高度分异的花岗质岩浆,而Nb、Ta质量分数说明成矿作用发生于酸性-弱酸性环境中;In_2O_3质量分数显示了成矿温度及压力从块状硫化物型矿石、矽卡岩型矿石、电气石细脉带型矿石、含锡白云岩型矿石到层间氧化矿型矿石有逐渐降低的趋势;云英岩型矿石中锡石的In_2O_3质量分数较高还需进一步论证。锡石形成过程中岩浆热液物理化学条件的变化导致其内部环带结构的形成,电子探针数据显示锡石的环带结构中化学成分呈"锯齿状"变化,显示成矿作用发生于动荡的环境中,说明锡石沉淀具有多期多阶段的特征。  相似文献   

7.
张士鲁 《矿床地质》1986,5(3):19-26
云南腾冲锡矿带是近几年才发现的。以往许多地质学者把东南亚锡矿向北延伸仅与云南境内的个旧锡矿相连接,因那时腾冲地区是个处女地。自七十年代末,本区开展了1/20万区调,发现了若干锡石重砂异常,与此同时,第四地质大队对旧矿点、老窿和铁帽露头取样分析,找到和评价了一批锡矿床,从而揭示了在滇西找锡的良好前景。  相似文献   

8.
略论个旧锡矿床地质找矿的新发现及其途径   总被引:11,自引:0,他引:11  
彭程电 《矿床地质》1986,5(3):37-48
个旧锡矿区是个矿产资源丰富,开采历史悠久的老矿区。据历史记载,矿床发现约在汉代(距今2100a左右)。元、明两代有少量开采,清康熙(1700a)以前多采冶银、铅,至清乾隆(1740a)以后采锡增加,清末产锡量已居世果第四位。解放后三十年来开展了大规模的地质勘探,探明了五大矿田几十处矿床,探获锡、铜、铅、钨等金属储量数百万吨。七十年代以来,随着勘探工作和矿山开采程度日益加深,地质找矿面临“深、新、隐”等问题。通过不断学习、探索和试验研究。我们在地质认识、找矿效果和方法手段等方面又取得了一些新进展。  相似文献   

9.
以云南大屯选矿厂锡粗精矿为研究对象,采用化学分析、X射线衍射分析及光学显微镜分析等手段对该粗精矿的化学组成、矿物组成、矿物嵌布粒度特征等进行了详细的研究。结果表明,锡粗精矿中有价元素锡的品位为13.80%,锡矿物主要以锡石形式产出。锡粗精矿中TFe含量为30.78%,主要以褐铁矿、磁黄铁矿的形式存在,磁黄铁矿是导致粗精矿含硫高的主要原因。锡粗精矿中主要的脉石矿物有白云石、透闪石、电气石、石英、白云母、萤石等,且脉石矿物与锡石均有不同程度的毗邻连生、包裹共生关系。本次工艺矿物学研究认为,大屯选矿厂锡粗精矿宜采用浮选预先脱硫,除去其中的硫化物,再对浮选尾矿采用重选工艺提高锡品位和回收率。该研究结果可以为大屯选矿厂工艺流程改造和合理开发利用锡资源提供科学依据。  相似文献   

10.
癞子岭岩体具有极好的垂向分带性,从下部到顶部包括了花岗岩、云英岩和伟晶岩,其中云英岩以其厚度巨大,云母类型属于铁锂云母,黄玉含量高,W-Sn-Nb-Ta含量高,而区别于其他地区云英岩。通过对癞子岭云英岩进行岩石学、地球化学和矿物学的研究,本文得出:癞子岭云英岩是高硅的强过铝质岩石类型,全碱含量低(3~4.3 wt%),富集挥发组分,全岩Zr/Hf(~8)和Nb/Ta(~1.7)比值低。造岩矿物铁锂云母中Nb(~74×10~(-6))、Ta(~66×10~(-6))、W(~23×10~(-6))、Sn(~75×10~(-6))等成矿元素含量较高。副矿物锆石自形且成分均一,含有HfO_2约10 wt%,Zr/Hf比值最低为5,与云英岩下部的癞子岭钠长花岗岩中的锆石成分有连续过渡的关系。这些特征与南岭地区高演化稀有金属花岗岩或伟晶岩相当,体现了相近的演化程度。癞子岭云英岩中有明显的Nb-Ta-W-Sn成矿作用发生,主要形成铌铁矿族矿物、锡石和黑钨矿,成分和结构均具有岩浆成因特征。花岗质熔体中含有大量挥发组分Li和F,结晶出黄玉和Li-F云母,F在稀有金属的成矿作用和云英岩的成岩过程中发挥了非常重要的作用,成矿作用发生在岩浆演化的晚期并伴随有流体作用。因此,云英岩可能是钠长花岗岩高度分异演化之后的特殊产物,这为研究花岗岩岩浆-热液体系成岩成矿过程提供了新的窗口。  相似文献   

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