Mineralogical and geochemical investigations of the Dajia Salento-type bauxite deposits,western Guangxi,China

The Dajia Salento-type bauxite deposit in western Guangxi is hosted within the Quaternary ferrallitic soil profile, and it formed via breaking up, weathering and oxidizing of Permian bauxite orebodies occurring as a semi-continuous layer in the upper Permian. Mineralogical analyses reveal that diaspore, hematite and kaolinite are the major minerals in bauxite ores with small amounts of anatase, chamosite, gibbsite, goethite, illite, zircon, quartz and pyrite. The ore texture and mineral assemblage reveal that the depositional/diagenetic environment of the Dajia bauxite was much close to phreatic environment. Both the ore texture and the morphology of zircon grains also indicate that most of the bauxitic soils were transported a short distance. Diaspore is suggested to be non-metamorphic in origin and mainly formed in a reducing condition of diagenetic environment, while kaolinite is the product of the in situ epigenetic replacement of alumina in diaspore by dissolved silica. Geochemical analyses indicate that Al₂O₃, Fe₂O₃, SiO₂ and TiO₂ are the main components of the bauxite ores and trace elements such as Zr, Hf, Nb, Ta, Th and U were enriched during the bauxitization process. Simultaneously, Zr vs. Hf and Nb vs. Ta show a high correlation. Geochemical indices such as Zr/Hf, Nb/Ta and Eu/Eu* (among others) denote that the magmatic rocks related to the Emeishan plume in western Guangxi and the carbonates in the underlying Maokou Formation provided the main sources of material for the bauxite ores.     

Detrital zircon records in bauxite deposits of China: Implication for the provenance model and ore deposits classification of bauxite

Based on 3439 detrital zircon U-Pb datapoints collected from the bauxite deposits of China and 297 detrital zircon U-Pb datapoints from underlying clastic rocks,this study reviews the recent progress in the detrital zircon U-Pb geochronology of bauxite deposits in China. Stability assessment of zircon grains in modern tropical weathering profiles proves the chemical and physical stability during the and intense weathering and bauxitization,which makes zircon become a good provenance indicator. Sedimentary provenance study of bauxite deposits in China indicates that even the bauxite deposit developed on the carbonate rocks,there was still considerable input of the weathering aluminosilicate materials. Previous classifications of bauxite deposit are mainly based on the lithology of basement rock and features of ore body,applications of these classifications will cause ambiguities and uncertainties. For widespread parautochthonous and allochthonous detrital zircon grains within Chinese bauxite deposits,parautochthonous and allochthonous criterion is invalid in classification of Chinese bauxite deposits. Here we suggest that the bauxite study requires a new classification of ore deposit,which should consider the weathering process of bauxite deposits as well as the position of bauxite deposit in the sedimentological framework. Although detrital zircon study provides important constrains for the provenance of bauxite deposits,combination of regional geological background and the geochemical characteristics are still essential for the comprehensive cognition of source materials.     

中国铝土矿沉积中的碎屑锆石记录: 对铝土矿物源模式与矿床分类的启示*

通过收集、整理和分析来自中国20个铝土矿床/矿点的3439个碎屑锆石U-Pb年龄数据以及297个来自铝土矿沉积下伏碎屑岩基底的碎屑锆石U-Pb年龄数据,对近年来中国铝土矿床的碎屑锆石年代学研究进展进行了综述。对现代热带地区红土剖面中锆石矿物稳定性评估认为在强化学风化条件下锆石颗粒仍然能保持化学与物理的稳定性,因此锆石是铝土矿沉积中良好的物源指示物。对中国铝土矿沉积物源研究表明,即使是形成在碳酸盐岩基底上的铝土矿,其中仍有大量硅铝酸盐沉积物风化产物的加入。此前的铝土矿床分类体系,多依照基岩岩性与矿体形态结构特征进行分类,在使用时可能会造成分类的模糊性与不确定性。中国铝土矿沉积中广泛存在指示准原地及异地成因的碎屑锆石组分,使用原地/异地指标也无法进行有效区分。基于以上原因,建议在考虑铝土矿分类方案时,除考虑铝土矿的风化产物属性外,还应对其作为沉积物/沉积岩的属性加以考量,新的铝土矿床分类方案是当前铝土矿研究中亟待解决的问题。此外,铝土矿的碎屑锆石年代学研究虽然为铝土矿物源研究提供了重要约束,但仍然需要结合区域地质背景及地球化学研究来提供更全面的铝土矿物源信息。     

重庆南川-武隆铝土矿矿物学、地球化学特征

重庆南川-武隆铝土矿属于渝南-黔北铝土矿成矿带,为喀斯特型铝土矿床。经显微镜、X射线粉晶衍射、矿物自动分析仪(MLA)、扫面电子显微镜等方法对该矿床矿物学的研究,发现组成铝土矿的主要矿物为一水硬铝石、高岭石、绿泥石,次要矿物为伊利石、一水软铝石、三水铝石、鲕绿泥石、菱铁矿、赤铁矿、针铁矿、黄铁矿、锐钛矿、金红石、磷灰石、石英、锆石、方解石、长石及稀土矿物等。矿石组构及矿物组合表明形成铝土矿的沉积/成岩环境为接近于潜流的环境。矿石结构和锆石形态指示成矿物质经过了短距离的搬运。地球化学研究结果显示,组成铝土矿的主要化学成分为Al₂O₃、TFeO、SiO₂和TiO₂,铝土矿化过程中REE、Zr、Hf、Nb、Ta、Th、Sc、Li和Ga发生富集。形成铝土矿的母岩物质主要来自下伏页岩的风化作用,灰岩和酸性火山岩对铝土矿的形成也有一定的贡献。结合稳定同位素资料,认为铝土矿的形成可能与生物作用有关。     

Mineralogical and geochemical investigations of the Mombi bauxite deposit,Zagros Mountains,Iran

The Mombi bauxite deposit is located in 165 km northwest of Dehdasht city, southwestern Iran. The deposit is situated in the Zagros Simply Fold Belt and developed as discontinuous stratified layers in Upper Cretaceous carbonates (Sarvak Formation). Outcrops of the bauxitic horizons occur in NW-SE trending Bangestan anticline and are situated between the marine neritic limestones of the Ilam and Sarvak Formations. From the bottom to top, the deposit is generally consisting of brown, gray, pink, pisolitic, red, and yellow bauxite horizons. Boehmite, diaspore, kaolinite, and hematite are the major mineral components, while gibbsite, goethite, anatase, rutile, pyrite, chlorite, quartz, as well as feldspar occur to a lesser extent. The Eh–pH conditions during bauxitization in the Mombi bauxite deposit show oxidizing to reducing conditions during the Upper Cretaceous. This feature seems to be general and had a significant effect on the mineral composition of Cretaceous bauxite deposits in the Zagros fold belt. Geochemical data show that Al₂O₃, SiO₂, Fe₂O₃ and TiO₂ are the main components in the bauxite ores at Mombi and immobile elements like Al, Ti, Nb, Zr, Hf, Cr, Ta, Y, and Th were enriched while Rb, Ba, K, Sr, and P were depleted during the bauxitization process. Chondrite-normalized REE pattern in the bauxite ores indicate REE enrichment (ΣREE = 162.8–755.28 ppm, ave. ∼399.36 ppm) relative to argillic limestone (ΣREE = 76.26–84.03 ppm, ave. ∼80.145 ppm) and Sarvak Formation (ΣREE = 40.15 ppm). The REE patterns also reflect enrichment in LREE relative to HREE. Both positive and negative Ce anomalies (0.48–2.0) are observed in the Mombi bauxite horizons. These anomalies are related to the change of oxidation state of Ce (from Ce³⁺ to Ce⁴⁺), ionic potential, and complexation of Ce⁴⁺ with carbonate compounds in the studied horizons. It seems that the variations in the chemistry of ore-forming solutions (e.g., Eh and pH), function of carbonate host rock as a geochemical barrier, and leaching degree of lanthanide-bearing minerals are the most important controlling factors in the distribution and concentration of REEs. Several lines of evidences such as Zr/Hf and Nb/Ta ratios as well as similarity in REE patterns indicate that the underlying marly limestone (Sarvak Formation) could be considered as the source of bauxite horizons. Based on mineralogical and geochemical data, it could be inferred that the Mombi deposit has been formed in a karstic environment during karstification and weathering of the Sarvak limy Formation.     

Cordilleran vein type Pb-Zn-polymetallic deposits of the Xidamingshan district, Guangxi, SW China: Fluid inclusion and geochemical studies

There are a lot of clastic-sedimentary-rock-hosted hydrothermal vein type polymetallic deposits in the Xidamingshan district, Guangxi, SW China. Two major ones of them, the Fenghuangshan Pb-Zn-Ag-Mn deposit and the Lujing Pb-Zn deposit, have been selected for fluid inclusion and geochemical research in this paper. From fluid inclusion microthermometry, it has been found that they were deposited from fluid with low salinities at medium to low temperatures and low pressures. From hydrogen, oxygen, sulfur and carbon stable isotope studies as well as some trace element composition of sulfides, we have got the conclusion that they were formed in an intrusion-related ore-forming system, which means that they belong to Cordilleran vein type deposits.     

Mineralogical and geochemical studies of brecciated ores in the Dalucao REE deposit,Sichuan Province,southwestern China

The Dalucao deposit, located in western Sichuan Province, southwestern China, in the western part of the Yangtze Craton, is one of the largest and most extensive rare earth element (REE) deposits in the Himalayan Mianning–Dechang REE belt. Moreover, the Dalucao deposit is the only deposit identified in the southern part of the belt. The Dalucao deposit contains the No. 1, 2, and 3 orebodies; the No. 1 and 3 orebodies are both hosted in two breccia pipes, located in syenite–carbonatite host rocks. Both pipes have elliptical cross-sections at the surface, with long-axis diameters of 200–400 m and short-axis diameters of 180–200 m; the pipes extend downwards for > 450 m. No. 1 and No. 3 have total thickness varying between 55 and 175 m and 14 to 58 m respectively. The REE mineralization is associated with four brecciation events, which are recorded in each of the pipes. The ore grades in the No. 1 and 3 orebodies are similar, and consist of 1.0%–4.5% rare earth oxides (REOs). The No. 1 orebody is characterized by a Type I mineral assemblage (fluorite + barite + celestite + bastnäsite), whereas the No. 3 orebody is characterized by a Type II assemblage (fluorite + celestite + pyrite + muscovite + bastnäsite + strontianite). Argon (⁴⁰Ar/³⁹Ar) dating of hydrothermal muscovite intergrown with REE minerals in typical ores from the No. 1 and 3 orebodies yielded similar ages of 12.69 ± 0.13 and 12.23 ± 0.21 Ma, respectively, which suggest that both mineral assemblages formed coevally, rather than in paragenetic stages. Both ages are also similar to the timing of intrusion of the syenite–carbonatite complex (12.13 ± 0.19 Ma). The ore-mineral assemblages occur in breccias, veinlets, and in narrow veins. The ore veinlets, which usually show a transition to mineralized breccia or brecciated ores, are commonly enveloped by narrow veins and stringer zones with comparable mineral assemblages. The brecciated ores form 95% of the volume of the deposit, whereas brecciated ores are only a minor constituent of other deposits in the Mianning–Dechang REE belt. The carbonatite in the syenite–carbonatite complexes contains high concentrations of S (0.07–2.32 wt.%), Sr (16,500–20,700 ppm), Ba (3600–8400 ppm), and light REEs (LREE) (2848–10,768 ppm), but is depleted in high-field-strength elements (HFSE) (Nb, Ta, P, Zr, Hf, and Ti). The syenite is moderately enriched in large-ion lithophile elements (LILE), Sr (155–277 ppm), and Ba (440–755 ppm). The mineralized, altered, and fresh syenites and carbonatites exhibit similar trace element compositions and REE patterns. Brecciation events, and the Dalucao Fault and its secondary faults around the deposit, contributed to the REE mineralization by facilitating the circulation of ore-forming fluids and providing space for REE precipitation. Some hydrothermal veins composed of coarse-grained fluorite and quartz are distributed in the syenite–carbonatite complex. The oxygen isotope compositions of ore-forming fluids in equilibrium with quartz at 215 °C are − 4.95‰ to − 7.45‰, and the hydrogen isotope compositions of fluid inclusions in coarse-grained quartz are − 88.4‰ to − 105.1‰. The syenite–carbonatite complex and carbonatite are main contributors to the mineralization in the geological occurrence. Thus, the main components of the ore-forming fluids were magmatic water, meteoric water, and CO₂ derived from the decarbonation of carbonatite. According to the petrographic studies, bastnäsite mineralization developed during later stages of hydrothermal evolution and overprinted the formation of the brecciated fluorite–quartz hydrothermal veins. As low-temperature isotope exchange between carbonates of the carbonatite and water-rich magmatic fluids will lead to positive shifts in δ¹⁸O values of the carbonates, C–O isotopic compositions from the bulk primary carbonatite to hydrothermal calcite and bastnäsite changed (δ¹⁸O_V-SMOW from 8.0‰ to 11.6‰, and δ¹³C _V-PDB from − 6.1 to − 8.7‰). According to the chemical composition of syenite and carbonatite, REE chloride species are the primary complexes for the transport of the REEs in the hydrothermal fluids, and the presence of bastnäsite and parisite means the REE were precipitated as fluorocarbonates. High contents of Sr, Ba and S in the syenite–carbonatite complex led to the deposition of large amount of barite and celestite.     

Mineralogical and geochemical evolution of the Bidgol bauxite deposit,Zagros Mountain Belt,Iran: Implications for ore genesis,rare earth elements fractionation and parental affinity

The present study focuses on the Late Cretaceous Bidgol bauxite deposit in the Zagros Simply Fold Belt, SW Iran. The orebody is located in the eroded major NW–SE trending Koh-e-Hosseyn anticline and hosted as discontinuous stratified layers and lenses within the upper member of the Cenomanian–Turonian Sarvak Formation. Detailed mineralogical analysis reveals that diaspore, hematite, goethite, anatase, clinochlore, chamosite, and calcite are the major mineral components accompanied by minor amounts of detrital and REE-bearing minerals such as rutile, zircon and parisite. The ore texture suggest that the bauxite material has an authigenic origin but in some parts it has been transported short distances from a primary in situ environment and redeposited in karstic depressions. The spheroidal pisolites of the Bidgol bauxite formed under conditions of low water activity, favouring the formation of large diaspore cores and a single dry-to-wet climatic fluctuation. The mass change calculations relative to the immobile element Ti show that elements such as Si, Fe, Mg, K, Na and Sr are leached out of the weathered system; Al, Ni, Zr, Ga, Cr and Ba are concentrated in the residual system; and Hf, Ta, Co, Rb, Cs, Be, and U are relatively immobile during the bauxitisation processes. The Nb, Th, Y, V, Sc, Sn and ΣREE are relatively immobile in the initial stage of bauxitisation processes in the bauxite ores, but were slightly mobile at the later stage of bauxitisation. Geochemical data reveal progressive enrichment of the REE and intense LREE/HREE fractionation toward the lower parts of the bauxite profile. Cerium behaves differently from the other REEs (especially LREE) and show positive anomalies in the upper horizons that gradually become negative in the deeper parts of the profile. The distribution and fractionation of trace elements and REEs during the bauxitisation process in the Bidgol deposit are mainly controlled by the presence of REE-bearing minerals, fluctuations in soil solution pH, REE ionization potential and the presence of bicarbonates or organic matter. Geochemical analyses confirm a protolith contribution from the bedrock argillaceous limestone and suggest that the source material for the Bidgol bauxite was provided from a siliciclastic material derived from a continental margin. The mid-Turonian uplift led to the formation of karstic topography, rubbly breccia and a layer of ferruginous–argillaceous debris that was affected by lateritic weathering under humid tropical climate. Subsequently, mobile elements are removed from the profiles, while Al, Fe and Ti are enriched, resulting in the formation of the pristine bauxite materials. When the platform subsided into the water again, the pristine bauxitic materials were partly converted to bauxite. During the exposure of bauxite orebodies on the limbs and crests of anticlines and subsequent eroding and accumulation in the karstic depressions during folding and faulting in Oligocene–Miocene, important factors such as intensity of the weathering, drainage and floating flow may have improved the qualities of the bauxite ores.     

河南省陕县支建矿区铝土矿沉积特征研究

支建铝土矿位于三门峡—新安铝土矿成矿带。通过对支建铝土矿的结构要素及成因、构造特征、沉积层序、主要组分变化与埋深、沉积环境、迁移和沉积方式的研究,初步建立了该区铝土矿的沉积模式,指出进一步的找矿方向,即在古陆周围深部煤系地层之下,仍能形成具工业意义的铝土矿体,这对河南省铝土矿找矿工作和煤矿的资源转型有一定的借鉴意义。     

河南卢氏-栾川地区铅锌矿成矿多样性分析及成矿预测

河南省卢氏-栾川地区位于华北陆块南缘与秦岭造山带的衔接部位,是中国重要的钼、钨、铅、锌多金属成矿区.通过控矿地质条件与成矿环境多样性分析,将研究区铅锌矿划分为3种成因类型岩浆热液交代型铅锌矿床、MVT型铅锌矿床和SEDEX型铅锌矿床.在此基础上,利用"成矿专属性"和"成矿多样性"相结合的找矿思路,对矿区不同类型矿床成矿进行远景评价,指出具有良好的找矿前景.     

微重力法与可控源音频大地电磁法组合在豫西寻找隐伏铝土矿中的应用

通过方法试验,在豫西地区已知铝土矿区的外围开展了1：5万高精度重力测量,发现绝大多数矿床点位于较平缓的重力梯度带上。：基底相对稳定的地段可作为铝土矿的找矿靶区;采用CSAMT（可按源音频大地电磁）法测深剖面,卡尼亚电阻率一频率曲线拐点可直接反映出新生界覆盖层和奥陶系灰岩层的埋藏深度,进而推断石炭系本溪组（铝土矿）的埋深。经10余个钻孔验证,见矿率达80％以上。试验结果证明,在地质研究的基础上,微重力法加上CSAMT法测深是寻找隐伏铝土矿的有效的方法组合。     

Mineralogical and geochemical patterns of mantle xenoliths from the Jixia region (Fujian Province,southeastern China)

The paper discusses the results of mineralogical and petrographic studies of spinel lherzolite xenoliths and clinopyroxene megacrysts in basalt from the Jixia region related to the central zone of Cenozoic basaltic magmatism of southeastern China. Spinel lherzolite is predominantly composed of olivine (Fo_89.6–90.4), orthopyroxene (Mg# = 90.6–92.7), clinopyroxene (Mg# = 90.3–91.9), and chrome spinel (Cr# = 6.59–14.0). According to the geochemical characteristics, basalt of the Jixia region is similar to OIB with asthenospheric material as a source. The following equilibrium temperatures and pressures were obtained for spinel peridotite: 890–1269°C and 10.4–14.8 kbar. Mg# of olivine and Cr# of chrome spinel are close to the values in rocks of the enriched mantle. It is evident from analysis of the textural peculiarities of spinel lherzolite that basaltic melt interacted with mantle rocks at the xenolith capture stage. Based on an analysis of the P–T conditions of the formation of spinel peridotite and clinopyroxene megacrysts, we show that mantle xenoliths were captured in the course of basaltic magma intrusion at a significantly lower depth than the area of partial melting. However, capture of mantle xenoliths was preceded by low-degree partial melting at an earlier stage.     

The role of microorganisms on the mineralogical and geochemical characteristics of the Parnassos-Ghiona bauxite deposits,Greece

The Parnassos-Ghiona bauxite deposits of Greece are hosted within carbonate rocks and have been formed during different geological ages. The most economically important deposits occur in the B3 bauxite horizon, which is developed over long distance as a continuous layer of 1–10 m in thickness, within Cretaceous limestones. Due to intense tectonics, a significant (approximately 30 vol.%) bauxite ores along and near their contact with faults show a brittle deformation and change in the color from red to black-gray, in a distance of tens of meter. Commonly gray to whitish bauxites are aluminum-enriched (> 65 wt.% Al₂O₃) and iron depleted.     

河南省三门峡地区铝土矿矿床地质特征及找矿方向

河南省三门峡地区的铝土矿是赋存于中石炭统本溪组中的一水硬铝石型铝土矿。以往的地质勘查找到了一些小、中、大型铝土矿矿床。对该地区铝土矿矿床地质特征及成矿规律进行了翔实研究,结果认为,在现有部分勘查区的深部和边部仍有较大的找矿潜力,若加大勘查投入,本区铝土矿的勘查工作将会达到一个新水平。     

河南卢氏—栾川地区铅锌矿成矿多样性分析及成矿预测

河南省卢氏-栾川地区位于华北陆块南缘与秦岭造山带的衔接部位,是中国重要的钼、钨、铅、锌多金属成矿区。通过控矿地质条件与成矿环境多样性分析,将研究区铅锌矿划分为3种成因类型:岩浆热液交代型铅锌矿床、MVT型铅锌矿床和SEDEX型铅锌矿床。在此基础上,利用“成矿专属性”和“成矿多样性”相结合的找矿思路,对矿区不同类型矿床成矿进行远景评价,指出具有良好的找矿前景。     

Petrogenesis of the Az Zabirah south zone bauxite ore deposits,central northern Saudi Arabia

Arabian Journal of Geosciences - The bauxite ore deposits are mainly found around the Az Zabirah area in the central northern part of Saudi Arabia. The age of the Az Zabirah bauxites was suggested...     

Geological,geochemical, and mineralogical characteristics of the Mandan and Deh-now bauxite deposits,Zagros Fold Belt,Iran

The Mandan and Deh-now bauxite deposits are located 40 km northeast of the Dehdasht city in the Zagros simply fold belt. These deposits occur in eroded major NW–SE trending anticlines and occupy karst cavities near or at the boundary between the Sarvak and Ilam Formations. Local uplifts at the end of the Cenomanian and the mid-Turonian caused erosion and karstification of the Sarvak Formation. These unconformities in the Upper Cretaceous favoured the formation and enrichment of bauxite deposits in the Zagros fold belt. The bauxite sequence in the Mandan deposit consists of white, gray, black, pisolitic, red, and yellow bauxites. This sequence was repeated in the Deh-Now area, but without gray and black bauxites. The present mineralogical studies of the Sarvak Formation and the Mandan and Deh-now bauxite deposits indicate oxidizing to reducing conditions during the Upper Cretaceous in the Zagros fold belt, which had a significant effect on the compositions of the bauxites. At least two phases of bauxitization can be distinguished in the study area: (i) an oxidizing phase represented by boehmite, diaspore, hematite and kaolinite; and (ii) a reducing phase represented by pyrite and chlorite. Geochemical data show that trace elements, like Zr, Hf, Nb, Ta, Th, and U, were enriched during bauxitization. The bauxite deposits and carbonate rocks show similar REE patterns, namely they are enriched in REEs although the LREEs are more enriched than the HREEs. Mass change calculations demonstrate that Mg, Mn, Ca, K, and P₂O₅ were leached out of the weathered system whereas Al, Fe, and Si become concentrated in the residual system. This study indicates that the Mandan and Deh-now deposits are karst-type bauxites formed by karstification and weathering of the Sarvak Formation.     

Genesis of the Guangou karstic bauxite deposit in western Henan,China

The Guangou bauxite deposit in western Henan, China, is located in the North China Block and to the north of the North Qinling orogenic belt. The orebody is hosted within the lower member of the Carboniferous Benxi Formation, which overlies unconformably upon the Ordovician Majiagou Formation. In the lower member of the Benxi Formation, the bauxite orebody (with a diaspore–illite–anatase mineral assemblage) is sandwiched between underlying ferric clay (illite–hematite–goethite) and overlying top clay (kaolinite–quartz–goethite). According to field observations and geochemical evidence including trace- and rare-earth-element (REE) compositions, especially Zr/Hf ratios, the ferric clays were weathered from the underlying argillaceous limestones in the Majiagou Formation. During this weathering process, trace elements S, Zn, Ni, Cr, V, Sc, F, Ba, and Be are depleted; Li, Rb, and B are enriched; and Zr, Hf, Bi, Ta, Ga, Nb, and Th are relatively immobile. REEs exhibit evident differentiation with enrichment of La, Ce, Pr, and Nd and depletion of Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The bauxite formed in weak reducing, slightly basic water conditions according to the geneses of coexisting diaspore and anatase, and it was altered during the epigenetic and second exposure periods, forming kaolinite and goethite, respectively. Interelemental relationship analyses of the ores suggest that the elemental behaviors of trace elements and REEs in the bauxitization process are mainly controlled by the mineral compositions in bauxite ore and chemical properties of the elements. For instance, zircon, rutile, and anatase contain Zr, Hf, Nb, Ta, W, and U. Based on geochemical evidence, together with age data and chemical compositions of the detrital minerals, both distant igneous rocks in the plate margin and Paleozoic carbonates and Precambrian rocks inside North China Block provide the miscellaneous material for the bauxite ore and the top clay.     

云南白秧坪地区东矿带矿床地质地球化学特征及成因分析

东矿带是云南白秧坪矿集区的重要组成部分,矿体明显受逆冲推覆构造主推覆断层及反冲断层的控制,多产于上三叠统三合洞组碳酸盐岩地层中。矿床中发育一套典型的中低温热液成因的矿物组合,成矿流体性质主要为来源于深部的中低温热卤水。硫、铅、碳、氧同位素分析表明成矿物质的深源特征,矿石稀土元素组成显示均有明显的δEu异常,构造热流体活动是成矿的主导因素。矿床地质地球化学特征显示,东矿带的矿床成因类型为与推覆构造有关的中低温热卤水铜银多金属矿床。