A new type of rare earth elements deposit in weathering crust of Permian basalt in western Guizhou, NW China

A new type of rare earth elements （REEs） deposit was discovered from the gaolinite mudstone in the weathering crust of Permian basalt, Bijie region, western Guizhou, China. It contained ∑RE2O3 0.065%-1.086%. This type of REEs deposit was widely distributed with steady horizon and thickness of 3-4 m. The ore-bearing weathering crust （kaolinite） of the three discovered REEs deposits belonged to the third episode of the Emeishan basalt eruption. The new type of REEs deposit was suggested that basalt （tuff） weathering could lead to the enrichment of the rare earth elements. Therefore, it is of important economic significance to explore REEs deposits in the weathering crust of basalt （tuffs） in Yunnan, Guizhou, and Sichuan Provinces.

A New Type of REE Deposit Found in Clay Rock at the Top of the Permian Emeishan Basalt in the Yunnan-Guizhou Area

Objective A set of REE-rich clay rocks is formed at the top of the Emeishan basalt in the eastern Yunnan-Western Guizhou area,accompanied by Nb,Zr,Ga.It is a new type of REE deposit and has great resource potential.This paper introduces its metallogenic conditions and element occurrence states,discusses the genetic mechanism.

Lead isotopic composition and lead source of the Tongchanghe basalt-type native copper-chalcocite deposit in Ninglang , western Yunnan , China

The Tongchanghe native copper-chalcocite deposit at Ninglang occurs in low-Ti basalts of western Yunnan, and the mode of fault-filling & metasomatism metallogenesis indicates that this deposit is of late-stage hydrothermal origin. This makes it more complicated to define the source of ore-forming materials. This paper introduces the Pb isotope data of Himalayan alkali-rich porphyries, regional Early-Middle Proterozoic metamorphic rock basement and various types of rocks of the mining district in western Yunnan with an attempt to constrain the origin of the Tongchanghe native copper-chalcocite deposit at Ninglang. The results showed that the ores are relatively homogeneous in Pb isotopic composition, implying a simple ore-forming material source. The three sets of Pb isotopic ratios in the Himalayan alkali-rich porphyries are all higher than those of the ores; the regional basement metamorphic rocks show a wide range of variations in Pb isotopic ratio, quite different from the isotopic composition of ore lead; the Pb isotopic composition of the Triassic sedimentary rocks and mudstone and siltstone interbeds in the Late Permian Heinishao Formation (corresponding to the forth cycle of basaltic eruption) in the mining district has the characteristics of radiogenic lead and is significantly different from the isotopic composition of ore lead; like the ores, the Emeishan basalts in the mining district and those regionally distributed possess the same Pb isotopic composition, showing a complete overlap with respect to their distribution range. From the above, the possibilities can be ruled out that the ore-forming materials of the Tongchanghe deposit were derived from the basement, a variety of Himalayan magmatic activities, etc. It is thereby defined that the ore-forming materials were derived largely from the Emeishan basalts. From the data available it is deduced that the native cupper-chalcocite-type metallogenesis that occurred in the Emeishan basalt-distributed area has the same metal source as the Tongchanghe deposit.

Platinum-group Elements Geochemistry of the Yangliuping Magmatic Ni-Cu-PGE Sulfide Deposit:Implications of Its Genetic Link with the Extrusive Basalts

Primitive mantle normalized Platinum group elements (PGE) concentration patterns for the Zhengziyanwo intrusion and Dashibao Formation basalts are of positive slope, similar to most of the world class magmatic Ni Cu PGE sulfide deposits. Characters of this intrusion and its related ores and Dashibao Formation basalts are their negative Pt anomaly and high concentration of Rh relative to Pt and Pd, facts being interpreted to be the results of crystallization and fractionation of Pt alloys and spinel phase free crystallization history for the magma, respectively. PGE parameters of the Dashibao Formation basalts are consistent with the general trend of those found for the Zhengziyanwo intrusion, and this might infer a genetic link between them.

Geochemical discrimination of the geotectonic environment of basaltic-andesitic volcanic rocks associated with the Laochang polymetallic ore deposit at Lancang, Yunnan

The Laochang polymetallic ore deposit at Lancang is one of the well known ancient ore deposits associated with volcanic rocks in the Sanjiang (Tri-river) region of Southwest China. Volcanic rocks are dominated by alkali basalt and trachyte basalt. There has long been a controversy on the environment of formation of basalts. Some scholars hold that the basalts were formed in a continental environment, some thought they were formed in an oceanic environment and others considered that the basalts were emplaced in a back-arc basin. This study focuses on the geochemical characteristics of the basalts on the basis of their major elements, REEs and trace elements. At the same time, strongly incompatible elements such as Ta, Th and Hf and their ratios were used to differentiate the geotectonic settings of basalts. The results showed that the basalts in the region studied were formed in a continental rift environment.

Geochemical Characteristics and Significance of Basalt in the Hongshiyan Pb-Zn-Cu Polymetallic Deposit in Southeastern Yunnan Province

1 Introduction Southeast Yunnan is the convergent place of the Yangtze,Indochina blocks(Xu Wei,et al.2008).The Hongshiyan Pb-Zn-Cu polymetallic deposit is located in Wenshan Prefecture,Yunnan Province.It is a typical large sized VMS-type deposit discovered in recent years.The major ore minerals are sphalerite,galena,chalcopyrite ect.

A preliminary study on ore-forming environments of Xianglushan-type iron deposit and the weathering mineralization of Emeishan basalt in Guizhou Province, China

Xianglushan-type iron deposits are one of the new types of iron deposits found in the Weining Area of Western Guizhou. The iron-bearing rock system is a paleo-weathered crustal sedimentary(or accumulating) stratum between the top of the Middle-Late Permian Emeishan basalt formation and the Late Permian Xuanwei formation. Iron ore is hosted in the Lower-Middle part of the rock system. In terms of the genesis of mineral deposit, this type of deposit should be a basalt paleo-weathering crustal redeposit type, very different from marine sedimentary iron deposits or continental weathering crust iron deposits. Based on field work and the analytical results of XRD Powder Diffraction, Electron Probe, Scanner Electron Microscope, etc., the geological setting of the ore-forming processes and the deposit features are illustrated in this paper. The ore-forming environment of the deposit and the Emeishan basalt weathering mineralization are also discussed in order to enhance the knowledge of the universality and diversity of mineralization of the Emeishan Large Igneous Province(ELIP), which may be a considerable reference to further research for ELIP metallogenic theories, and geological research for iron deposits in the paleo-weathering crust areas of the Emeishan basalt,Southwestern, China.

贵州盘州市架底金矿床地质特征及找矿方向

架底金矿是近年贵州西部发现的最大原生金矿床,以玄武岩为容矿岩石的微细浸染型金矿。赋矿部位为上层破碎蚀变带和下层构造蚀变体,均为区域构造作用和热液蚀变的综合产物。本文基于架底金矿床地质特征及金矿体在玄武岩区富集规律的总结,分析外围找矿方向,对该地区外围寻找玄武岩容矿金矿床具有实践指导意义。

Geological significance of nickeliferous minerals in the Fule Pb–Zn deposit, Yunnan Province, China

The Fule Pb–Zn deposit is located in the Sichuan–Yunnan–Guizhou Province, and it is an important and giant low temperature metallogenic domain in China.In our research area, the Pb–Zn deposits are mainly hosted in the Permian Yangxin Formation and are composed of dolostone and limestone. The distance between the ore bodies and the Permian Emeishan basalt ranged from 50 to160 m. In this study, the nickel rich minerals, including vaesite, polydymite and millerite, were reported for the first time in the Fule deposit. These minerals occurred as xenomorphic mineral aggregate and were sporadically distributed in the sphalerite–galena–calcite vein, which is the main ore type in the deposit. Our study indicated that the paragenetic sequence of minerals in the Fule deposit is the following order: polydymite → vaesite→ millerite → sphalerite → galena → tetrahedrite(tennantite).The geological occurrence characteristics of those nickeliferous minerals suggested that the Permian Emeishan basalt is a possible barrier layer of Pb–Zn ore-forming fluid, and it is an important source for the Ni and part of the Cu in the deposit. The Sichuan–Yunnan–Guizhou Pb–Zn mineralization province is a world-class production base of Pb and Zn, in which the Permian Emeishan basalt and Pb–Zn deposits have uniformly spatial distribution, but the relationship of mineralization between them is still under debate. This report provides new evidence forunderstanding the relationship between Pb–Zn mineralization and Permian Emeishan basalt in the Sichuan–Yunnan–Guizhou Pb–Zn mineralization province.

Modeling experimental study on weathering-leaching of Emeishan basalt and its relation with metallogenesis

The Emeishan basalt has a high Cu background value (170×10-6 on average), and thus provides a ore-forming material source for copper ores. The collected samples were exposed in basalt lavas of the third segment of the Emeishan basalt eruptive cycle. By using a set of automatically cycling glass apparatuses, weathering-leaching experiments by three kinds of rainwater on the collected samples were carried out in the open system (at normal temperature and normal pressure). The analysis results showed that the most intensive export of Cu occurred under acidic rainwater-induced weathering-leaching conditions, almost 2-3 orders of magnitude the export of Cu by mod-ern air rainwater, and 1-2 orders of magnitude higher than the export of Cu by CO2 rainwater. In addition, the total amount of Zn, Cu, U, Ni and Sr exported by acidic rainwater are greater than 1%. All this indicates that copper in the Emeishan basalt provided the copper source for Cu mineralization at the contact between the basalt and the Maokou Formation limestone at the bottom.

Zircon U–Pb dating and whole-rock elemental geochemistry of the Shazi anatase deposit in Qinglong,Western Guizhou,SW China

The Shazi deposit is a large-scale anatase deposit in Qinglong, Guizhou Province. Zircon grains from this deposit yielded a zircon U–Pb age of *259 Ma, representing the formation age of the deposit's parent rocks.This age is identical to the eruption age of the Emeishan large igneous province, indicating a synchronous magmatic event. The rare-earth-element patterns of laterite samples were similar to those of the weathered basalt sample, and sub-parallel to those of the Emeishan high-Ti basalts,implying a genetic relationship between the laterite and the basalt. The Chemical Index of Alteration values of laterite ranged from 96 to 98, suggesting a high degree of weathering. SiO_2, MgO, and alkaline metal elements decreased with increasing degree of weathering, while Al_2O_3, Fe_2O_3,and TiO_2 increased. We found the highest TiO_2 in laterite and the lowest in pillow basalts, indicating that Ti migrated from basalt to laterite.Our U–Pb dating and whole-rock elemental geochemistry analyses suggest that the Emeishan basalt is the parent rock of the Shazi anatase ore deposit.Based on our analysis, we propose a metallogenic model to explain the ore-forming process, in which the karst terrain formed by the Emeishan mantle plume and the subsequent basaltic magma eruption were the key factors in the formation the Shazi anatase ore deposit.

Geochemistry and genesis of the Nadun Nb-enriched arc basalt in the Duolong mineral district,western Tibet:Indication of ridge subduction

The Duolong mineral district in western Tibet is one of the largest porphyry Cu–Au deposit fields with significant metallogenic potential in China.Its tectonic environment relevant to Early Cretaceous Cu–Au mineralization remains controversial.Here we report new whole-rock major and trace element,and Sr-Nd-Hf-Pb isotopic data for the newly discovered basalt in the Nadun area,Duolong mineral district,to decipher their genesis and further constrain the tectonic environment.A contemporaneous rhyolite sample interbedded with the basalt in the lower part of the volcanic section in the Nadun area yields an LA-ICP-MS zircon U–Pb age of 122.5±1.2 Ma.The basalt samples exhibit high-K calc-alkaline/shoshonite properties and are enriched in high field strength elements,e.g.,high Ti O_(2)(1.43–1.79 wt.%)and Nb(14.6–19.5 ppm)contents,with high Nb/La ratios(0.4–0.6),which are compositionally comparable to those of Nb-enriched arc basalts(NEABs).The(^(87) Sr/^(86) Sr)iratios of 0.7052 to 0.7056,negative eNd(t)(-0.7 to-0.2)and eHf(t)values(+6.0 to+6.5),and high(^(206) Pb/^(204)Pb)i,(^(207) Pb/^(204)Pb)i,(^(208) Pb/^(204)Pb)iand ratios(18.522 to 18.561,15.641 to 15.645 and 38.679 to 38.730,respectively)suggest that the Nadun NEABs are more enriched than those of the island arc basalts(IABs)in the area.The slightly enriched radiogenic isotopes for the Nadun NEABs indicate that the subducting sediments play an important role in the source.Furthermore,their high Nb,Ti,and Cu contents indicate that the source mantle wedge was metasomatized by slab melts.The Nadun NEAB and other coeval magmatic rocks in the Duolong mineral district,including adakite,OIB-like basalt,MORB-type basalt,A-type rhyolite,and common IAB,are typical rock assemblages of ridge subduction.We infer that the Duolong mineral district were formed by ridge subduction in the Early Cretaceous.

Study on the geological conditions of metallogenesis of the Shazi large-scale anatase deposit in Qinglong County, Guizhou Province

The Shazi large-scale anatase deposit in Qinglong County, Guizhou Province, has been discovered recently and now is under exploration. Investigations show that the orebodies mostly occur at the top of the karst unconformity of the Middle Permian Maokou Formation strata and at the bottom of the Emeishan basalt. And the following three prerequisites should be satisfied for the formation of the deposit: 1) there must be the material source of anatase; 2) there must be weekly alkaline media and low-tempeature and low-pressure conditions; 3) there was no high-temperature and high-pressure environment subsequently for the transformation of anatase into rutile. In the Emeishan basalt of western Guizhou, the element Ti mostly entered the silicon-oxygen tetrahedra of picrite in heterovalent isomorphism(Ti4++Al3+→Mg2++Si4+). When volcanic ejecta resultant from strong eruption of the Emeishan basalt magma fell into water, picrite was usually dissociated to chlorite. Thus, the element Ti4+ in the picrite could be released from the silicon-oxygen tetrahedraa of picrite into water, and conbined with oxygen in the water to form Ti O2. This paper has proved that this deposit, enriched in anatase, discovered recently at Shazi, Qinglong Country, Guizhou Province, is a residual-deluvial-type deposit. Its genesis can be explained as follows. Volcanic clastics formed at the early stage of strong eruption of the Emeishan basalt magma were chemically deposited to form anatase in the low-temperature, low-pressure and weekly alkaline waters in the karst depressions at the top of the Maokou Formation(limestone) strata. The anatase was then dissociated owing to weathering and leaching during the Quaternary and the anatase was further enriched to form the residual-deluvial-type anatase ore deposit.

Study on the element geochemical charactersitics of the Shazi large-sized anatase ore deposit in Qinglong, Guizhou Province

The Shazi anatase ore deposit in Qinglong, Guizhou Province, is a large-sized anatase deposit that has been recently explored. The characteristics of major oxides in the ore are similar to those of modern laterite weathering crust and laterite in the laterite-type gold deposits in the western part of Guizhou Province. Studies on the REE characteristics of basalts and anatase ores in the study region showed that both of them do have extremely strong affinities. There are two groups of trace elements in the ores, i.e., Au-Ag-As-Sb-Hg-Tl association and Sc-TiO2-Cu-Fe-Mn association, reflecting that the formation of anatase ore is related to the formation of siliceous claystone at the early stage of eruption of the Emeishan basaltic magma. The siliceous claystones are the major country rocks for the formation of laterite-type gold ores and anatase ores. In the region anatase ores are rich in Sc and the basalts enriched in Fe, Mn, Ti and Sc are the material source of metallogenesis.

Implication of Paleoproterozoic Basalt Fertility Related to Mantle Plume Activity in Nassara Gold Mineralization (Burkina Faso, West Africa)

The Birimian Nassara volcanic formations are located south of Gaoua in the southern part of the Boromo belt. Within these formations is the Nassara gold deposit where mineralization is hosted at the contact between basaltic volcanic rocks and sedimentary rocks. It is with the aim of understanding the geodynamic context of the basaltic rocks and the implication of their primary gold potential in the Nassara gold deposit that this work is carried out. To achieve our objectives, 28 samples of fresh basaltic rocks were geochemically analyzed for their major and trace element compositions. These analyses show that the Nassara basalts are Fe-rich tholeiitic basalts. Rare earth profiles (La/SmN = 0.75 - 1.50;La/YbN = 0.65 - 2.18) are fairly flat and without europium anomaly (Eu/Eu* = 0.90 - 1.09), nor niobium. In the Zr/Nb vs. Nb/Th and Nb/Y vs. Zr/Y binary diagrams, the Fe-rich tholeiitic basalts of Nassara, as well as those of the Houndé and Boromo belts, are placed in the field of oceanic plateau basalts related to a mantle plume system. A gold fertility test carried out on these basalts was positive. As other studies have already shown, the genetic link between gold deposits and mantle plumes appears to be a general rule. The scenario for the Nassara gold deposit is that it is the source magma that was already more or less enriched in gold and other related elements on its way up. The remobilization of this gold would have occurred during the Eburnean orogeny with the help of metamorphic, hydrothermal and deformation phenomena to be redeposited at the level of shear zones with economic grades. Through this analysis, we show that the fertility of the initial lithologies is very important for the formation of economic size deposits in the proximal shear zones. Exploration work should now integrate this dimension to define the best targets.

黔西南两类容矿围岩金矿对比及对深部找矿勘查的指示

黔西南是中国著名的卡林型金矿集区,已查明金资源量约750 t,特别是近年来在该地区新发现了玄武岩容矿金矿,以架底大型金矿床、大麦地中型金矿床为典型代表,取得了新的找矿突破和认识,至此,该地区原生金矿容矿围岩主要有玄武岩和沉积岩两类。通过对黔西南玄武岩容矿金矿与沉积岩容矿金矿进行对比分析研究,认为:(1)卡林型金矿的定义可能存在一定局限性,需进一步拓展,黔西南玄武岩容矿金矿与沉积岩容矿金矿典型特征相似,可能形成于同一区域成矿事件,是同一区域岩浆热液成矿作用形成的卡林型金矿,在深部勘查与研究工作中应系统考虑;(2)构造(背斜、穹隆、断裂、SBT)+有利岩石组合(厚度大于100 m的碳酸盐岩与上覆厚度大于50 m的碎屑岩或玄武岩/凝灰岩)+Au-As-Sb-Hg-Tl组合异常+围岩蚀变(硅化、黄铁矿化、毒砂化),可能指示深部存在卡林型金矿;(3)玄武质岩石也是卡林型金矿很好的赋矿围岩,卡林型金矿容矿岩石、容矿地层具有多样性,几乎区内所有岩石和地层均可以成为卡林型金矿的容矿岩石和容矿地层,但具体到某一个特定的矿床时,往往有特定的就位地层和特殊的容矿围岩。

四川省峨边地区峨眉山玄武岩岩石特征及纤维用玄武岩矿特征分析

峨边地区出露的二叠纪峨眉山玄武岩组地层多以溢流相为主,岩石呈深灰色-灰绿色,根据其成因及结构组分特征,可将峨边地区峨眉山玄武岩划分为斑状玄武岩、致密玄武岩、气孔-杏仁玄武岩、凝灰质玄武岩四种岩石类型。并对玄武岩岩石、化学特征开展研究,研究表明区内存在符合拉丝的纤维用玄武岩,具有较好的开发利用前景。

基于3DMine的云南省官房铜矿矿体三维建模及深部找矿预测

官房铜矿是云南目前所发现的规模较大的玄武岩型铜矿床之一。现已控制铜金属资源量近50万t,目前主采矿段向阳山矿段矿石储量接近枯竭,寻找新的接替资源成为当下的重点工作。研究通过野外及井下地质调研,在前人的研究成果基础上,以官房铜矿矿区向阳山矿段为研究对象,结合对成矿地质条件的认识和实测勘探线,运用3DMine建模软件,构建了向阳山矿段矿体三维地质模型。通过对官房铜矿成矿规律的总结,以向阳山矿体三维模型为基础,进行了深部找矿预测,圈出有利找矿空间2处。

川东华蓥山褶皱带西天超大型玄武岩矿床地质特征及岩石成因

通过野外和镜下岩相学观察,结合主、微量元素地球化学方法,研究了四川省广安市邻水县西天超大型纤维用玄武岩矿床的地质特征,分析了矿石工业指标和矿床成因.结果表明:矿床位于川东褶皱带华蓥山背斜东翼,矿体呈似层状赋存于上二叠统峨眉山玄武岩组(P3β)地层中,矿石储量约1594×10^(4)t,达超大型规模;主量元素地球化学特征表明,西天玄武岩岩浆属高钛、高钾钙碱性-钙碱性系列;稀土元素、微量元素地球化学特征与区域内高钛峨眉山玄武岩及OIB型玄武岩特征相似;西天玄武岩为峨眉山大火成岩省的外带组成部分,形成于板内构造环境,岩浆演化来源于OIB型源区且基本未受地壳物质混染,为地幔热柱成因的产物;矿床中的柱状节理玄武岩、块状玄武和气孔状玄武岩可用于纤维拉丝生产.

云南省麻栗坡县杨万铜矿矿床成因机制分析

杨万铜矿床位于云南东南麻栗坡县的八布海相火山岩中。该地区地质构造复杂,岩浆活动频繁,成矿地质条件得天独厚,是我国铜矿资源勘查基地之一。该区域内已发现的铜矿床点分布广泛,其中火山岩为赋矿围岩的铜矿床赋矿层位众多、规模庞大、品位较高,成为该区重要的矿床类型,备受业界关注。以往的地质调查和研究已经对杨万铜矿的矿化特征和矿床成因进行了深入探究,然而在杨万铜矿床的矿床成因机制分析方面,前人的研究仍存在一定的局限性。为此,本次工作系统总结了前人的勘查工作和研究成果,结合本次勘查工作,并对研究成果进行了验证、对比和推演分析。通过这些工作,对杨万铜矿床成因机制有了更为全面的认识。