scholarly journals Sequential Scheelite Mineralization of Quartz–Scheelite Veins at the Sangdong W-Deposit: Microtextural and Geochemical Approach

Minerals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 678
Author(s):  
Woohyun Choi ◽  
Changyun Park ◽  
Yungoo Song ◽  
Chaewon Park ◽  
Ha Kim ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Hanging Wall ◽  
Geochemical Characteristics ◽  
Stage Ii ◽  
Oscillatory Zoning ◽  
Ore Deposit ◽  
Vein System ◽  
Pressure Release ◽  
System Pressure ◽  
Mo Content

The Sangdong W (tungsten)-deposit is known as one of the world’s largest W-deposits, a magmatic–hydrothermal ore deposit including both skarn and hydrothermal alteration zones. The strata-bound characteristic of the deposit resulted in three major orebodies (hanging wall, main, footwall). The main ore mineral is a scheelite (CaWO4)–powellite (CaMoO4) solid solution. We examined the fluid evolution and scheelite formation process of the quartz–scheelite veins of the ore deposit, based on the microtextures and geochemical characteristics of the scheelite. After the initial magmatic–hydrothermal fluid release from the granitic body, prograde skarn is formed. In the later prograde stage, secondary fluid rises and precipitates stage I scheelite. Well-developed oscillatory zoning with the highest Mo content indicates continuous fluid infiltration under an open system. Pressure rises as mineralization occurs, generating the pressure release of the retrograde fluid. Fluid migrates downward by the gravitational backflow mechanism, forming stage II to IV scheelites. Dented oscillatory zoning of stage II scheelite is strong evidence of this pressure release. Stage III and IV scheelite do not show specific internal structures with pure scheelite composition. Retrograde scheelites are formed by fractional crystallization under a closed system. The observation of systematical fractional crystallization in the quartz–scheelite vein system is a meaningful result of our research. The geochemical characteristics and microtextural evidence imprinted in scheelites from each stage provide crucial evidence for the understanding of sequential scheelite mineralization of the quartz–scheelite vein system of the Sangdong W-deposit.

Telluride Mineralogy of the Deer Horn Au-Ag-Te-(Bi-Pb-W) Deposit, British Columbia: Implications for the Generation of Tellurides

2021 ◽  
Author(s):  
Jordan A. Roberts ◽  
Lee A. Groat ◽  
Paul G. Spry ◽  
Jan Cempírek
Keyword(s):  
British Columbia ◽  
Fluid Inclusions ◽  
Hanging Wall ◽  
Oscillatory Zoning ◽  
Stage Iii ◽  
Fine Grained ◽  
Melting Temperatures ◽  
Homogenization Temperatures ◽  
Intrusive Suite ◽  
Cathodoluminescence Imaging

ABSTRACT The Deer Horn deposit, located 150 km south of Smithers in west-central British Columbia, is an Eocene polymetallic system enriched in Au-Ag-Te with lesser amounts of Bi-Pb-W; the Au and Ag are hosted in Te-bearing minerals and Ag-rich gold (Au-Ag alloy). A quartz-sulfide vein system containing the main zones of Au-Ag-Te mineralization and attendant sericite alteration occurs in the hanging wall of a local, spatially related thrust fault and is genetically related to the nearby Eocene Nanika granodiorite intrusive suite. Tellurium-bearing minerals commonly form isolated euhedral to subhedral grains or composite grains (up to 525 μm in size) of Ag-, Bi-, Pb-, and Au-rich tellurium-bearing minerals (e.g., hessite, tellurobismuthite, volynskite, altaite, and petzite). Panchromatic cathodoluminescence imaging revealed four generations of quartz. Within remnant cores of quartz I, local oscillatory zoning occurs in quartz II. Fine-grained veinlets of quartz III and IV crosscut quartz I and II, showing evidence of at least two deformation events; late-forming veinlets of calcite crosscut all generations of quartz. The tellurides and Ag-rich gold occur in stage III quartz. Three types of fluid inclusions were observed in stage III and IV quartz: (1) aqueous liquid and vapor inclusions (L-V); (2) aqueous carbonic inclusions (L-L-V); and (3) carbonic inclusions (vapor-rich). Primary fluid inclusions related to the telluride mineralization within quartz III were tested with microthermometry, along with a few primary inclusions from quartz IV. Homogenization temperatures are 130.0–240.5 °C for L-V inclusions and 268.0–336.4 °C for L-L-V inclusions. Aqueous carbonic inclusions had solid CO2 melting temperatures from –62.1 to –56.8 °C, indicating the presence of ≈1 to 30 mol.% dissolved methane in these inclusions. The Deer Horn Au-Ag-Te-(Bi-Pb-W) deposit is a reduced intrusion-related gold system characterized by sheeted veins, metal zoning, low salinity aqueous-carbonic fluids, and a genetic relationship to an Eocene granodiorite. Values of δ34S of pyrite vary from –1.6 to 1.6 per mil and are compatible with a magmatic source of sulfur.

Geochemical Anomaly Characteristics of the Soil Secondary Halo of Pangjiagou Gold Polymetallic Deposit in Chengde, Hebei Province

2013 ◽  
Vol 807-809 ◽  
pp. 2129-2132
Author(s):  
Jiao Jiao Chen ◽  
Ying Shu Li ◽  
Da Qing He ◽  
Dong Ming Yang ◽  
Yi Ke Zhang
Keyword(s):  
Surface Oxidation ◽  
Wall Rock ◽  
Hydrothermal Activity ◽  
Ore Deposits ◽  
Hebei Province ◽  
Geochemical Characteristics ◽  
Geochemical Anomaly ◽  
Ore Deposit ◽  
Polymetallic Deposit ◽  
North East

Pangjiagou gold polymetallic deposit is located in bending parts of the north east direction of the Yanshan arc structural belt in Hebei province, which has a good regional metallogenic background. According to the collection of samples and tests of eight elements for the samples of the mining area, we studied the geochemical anomaly characteristics of the soil secondary halos of the ore deposit. By means of researching on geochemical characteristics of the ore deposit, it worked out that the ore deposit possesses the characteristics of multiphase ore-forming hydrothermal activity, which is divided into the Sb-Zn mineralization period and Cu-Au mineralization period. The important prospecting of the ore deposits in the area consist of the surface oxidation, the wall rock alteration and the geochemical characteristics.

Hierarchical fuzzy-AHP-based multi-criteria decision making approach for selection of underground metal mining method

2021 ◽  
Vol 15 (3) ◽  
pp. 405-420
Author(s):  
Bhanu Chander Balusa ◽  
Amit Kumar Gorai
Keyword(s):  
Decision Making ◽  
Underground Mining ◽  
Fuzzy Ahp ◽  
Hanging Wall ◽  
Ore Deposits ◽  
Mining Method ◽  
Metal Mining ◽  
Extrinsic Factors ◽  
Ore Deposit ◽  
Mining Methods

In the last few decades, many underground mining methods were proposed for extractions of ores. The decision-making for selecting the most suitable mining method for a typical ore depost depnds on various intrinsic and extrinsic factors (intrinsic – dip, shape, thickness, depth, grade distribution, RMR (rock mass rating) and RSS (rock substance strength) of ore, hanging wall, footwall, and extrinsic – recovery, dilution, safety, productivity, flexibility, capital). The present study aims to develop a hierarchical Fuzzy-AHP (FAHP) model for choosing the most suitable underground mining method for an ore deposit. The structure of the proposed hierarchical FAHP model consists of five levels. The level-1 of the hierarchy defines two variables (intrinsic factors and extrinsic factors). These are further classified into quantitative or qualitative nature of variable (listed in level-2). The criteria, sub-criteria, and mining method variables are listed respectively in Level 3, Level 4, and Level 5. For each level of the hierarchy, a fuzzy pair-wise comparison matrices are developed using the corresponding levels’ listed variables. These matrices at each level are subsequently used to determine the local and global weights of each variable. The global weights are used for prioritizing the different mining methods. The proposed hierarchical FAHP model was validated by considering the field data of two different ore deposits in India. The results showed that the most appropriate mining method predicted from the decision-making model and the adopted mining method for extracting the ore deposit are same in two case studied mines.

The Youngest Toba Tuff (74 ka) Crystals Characterization

2020 ◽  
Author(s):  
Gabriela Nogo Retnaningtyas Bunga Naen ◽  
Atsushi Toramaru ◽  
Tomoharu Miyamoto ◽  
Haryo Edi Wibowo
Keyword(s):  
Magma Chamber ◽  
Fractional Crystallization ◽  
Optical Microscope ◽  
Oscillatory Zoning ◽  
Geochemical Data ◽  
Thin Sections ◽  
Decompression Rate ◽  
Wide Range ◽  
Different Characteristics ◽  
Toba Caldera

<p>Toba Caldera Complex, Indonesia is well known as the largest Quaternary caldera (87x33 km) that formed by four major eruptions among which the biggest one is the eruption of the Youngest Toba Tuff (YTT) about 74,000 years ago. Textural study of the pumice clast from YTT has been done to estimate the decompression rate by using bubble number density data. The result shows that decompression rate of Toba Caldera forming eruption varies in two order magnitude ranging from 10<sup>6 </sup>– 10<sup>8</sup> Pa/s. Southern pumices show the lower value than pumices from northern caldera. Similarly, new data about lithic distributions and mineral components of YTT from the northern and southern caldera showed several different characteristics. This fact suggests possibility of different processes which is distinguish production of southern and northern deposits. Therefore, understanding both conduit and chamber processes is needed to reveal the origin of differences in deposits. This study aims to elucidate magma chamber condition by characterizing the deposit especially crystals from YTT eruption.</p><p>Characterizations of Toba Tuffs have been made but not been enough to discuss YTT in detail. In this study, we focus on spatial differences in YTT deposits. Samples from four different locations were employed for the analyses. Component analysis was carried out on components larger than 2 mm. Whole-rock geochemical data were obtained by XRF. Petrography analysis for 37 thin sections was conducted using optical microscope. Textural analysis was carried out for 84 free crystals and 25 selected thin sections using microphotographs taken by SEM and further analyzed using image processing software. Chemical analysis for free crystal was carried out by SEM-EDS, while for pumices grain of 22 thin sections was conducted using EPMA.</p><p>Geochemical data showed that YTT magma is rhyodacitic to rhyolitic in whole-rock compositions with wide range of SiO<sub>2</sub> (69.15–76.83 wt.%). There are differences in abundance and type of pumices, free crystals, and lithic in each location<strong>.</strong> Major minerals are plagioclase, biotite, sanidine, and quartz. Common characteristics of northern and southern part deposit is that most of crystals are fractured, some forming aggregates, has anhedral shape and wide variation in size (0.003 mm<sup>2</sup>-13.113 mm<sup>2</sup>). However, there are differences between northern and southern deposits: presence of amphibole with larger size, orange quartz, sieve texture, patchy zoning, oscillatory zoning, crystal clots, and wider range of anorthite (An<sub>25</sub>– An<sub>87</sub>) is mostly found in northern deposits.</p><p>Plagioclase composition from northern part shows bimodal distribution suggesting that crystallization does not occur simultaneously by single process. Furthermore, plots of anorthite number versus size and of average anorthite number versus crystal content show random distribution, suggesting the complex crystallization of plagioclase: other processes than fractional crystallization in magma chamber. Moreover, presence of antecryst and disequilibrium textures in northern deposit indicates intervention from older rocks or even other systems. Different characteristics between northern and southern deposits suggest that YTT deposits are generated by multiple eruptions from independent, at least two magma chambers.</p><p>Keywords: Toba Caldera, the Youngest Toba Tuff (YTT), Crystal Characterization, Conduit Process, Chamber Process, Fractional Crystallization, Multiple eruptions</p>

Study on Geochemical Characteristics of the Sb Polymetallic District in Da Zhuang of Kai Yuan County in Yunnan Province

2013 ◽  
Vol 807-809 ◽  
pp. 2184-2187
Author(s):  
Jiao Jiao Chen ◽  
Ying Shu Li ◽  
Yi Ke Zhang ◽  
Da Qing He ◽  
Dong Ming Yang
Keyword(s):  
Yunnan Province ◽  
Mineral Resources ◽  
Mining Area ◽  
Geochemical Characteristics ◽  
Geochemical Data ◽  
Geological Investigation ◽  
Ore Deposit ◽  
Structure Characteristics ◽  
Yunnan Area ◽  
Favorable Conditions

Southeast Yunnan Area is an Important Nonferrous Metals Mineral Resources Base in Yunnan Province, with Good Metallogenic Conditions. the Structure Characteristics of Kai Yuan Da Zhuang Mining Area is more Complex, with Favorable Conditions for Mineralization. Based on Detailed Geological Investigation, Combined with the Geochemical Data and Geological Setting, Deposit Features of Da Zhuang Antimony Ore Deposit and Summarizes Geochemical Characteristics, that is to Study the Genesis of this Deposit and is to Predict the Mining Ore.

scholarly journals Kremeňovo-karbonátové žily s U-Mo-Cu mineralizáciou v permských intermediárnych až bázických vulkanitoch hronika na lokalite Kravany (Kozie chrbty, východné Slovensko)

2020 ◽  
Vol 28 (2) ◽  
pp. 364-384
Author(s):  
Štefan Ferenc ◽  
Tomáš Mikuš ◽  
Ján Spišiak ◽  
Richard Kopáčik ◽  
Eva Hoppanová
Keyword(s):  
S Phase ◽  
Point Of View ◽  
Upper Permian ◽  
Ore Deposit ◽  
Clastic Sediments ◽  
Ore Minerals ◽  
Basic Volcanics ◽  
Basin Formation ◽  
Mo Content ◽  
Geological Position

Historical uranium ore deposit Kravany is located in the eastern part of Kozie Chrbty Mts., approximately 9 km SW of the district town Poprad. Stratiform, infiltration U-Cu-Pb mineralization is bound to the Upper Permian clastic sediments (Kravany Beds, member of Malužiná Formation, Hronicum Unit), which are enriched in fragments of carbonized flora. Vein U-Mo-Cu mineralization was found in the Upper Permian intermediate to basic volcanics intersecting the sediments of the Kravany Beds (also ore lenses). Vein filling originated in the following development stages: I.) Quartz-pyrite (quartz, pyrite, marcasite), II.) Dolomite-pyrite (dolomite, pyrite, marcasite, galena), III.) Copper (tetrahedrite, tennantite, chalcopyrite), IV.) Uranium-molybdenum (uraninite, Pb-Mo-S phase, coffinite, quartz), and V.) Calcite (calcite, chalcopyrite). The formation of mineralization can be explained by the geological position: random emplacement of the diorite porphyrite, resp. basalt-andesite dikes, directly in the preexisting U,Mo-bearing sediments. Vein U-Mo-Cu mineralization could thus most likely have formed according to the following scenario: I.) sedimentation of Kravany Beds in the Permian riftogenic basin: formation of beds of arkoses and arkosic sandstones with abundant fragments of charred flora, II.) formation of infiltration U mineralization: reduction and accumulation of U in sediments rich in organic matter, III.) emplacement of dikes of intermediate to basic volcanics: intersection of sediments with organics and with high U and Mo content, mobilization of formation fluids, assimilation of U and Mo into intermediate-basic magma, IV.) cooling of volcanic bodies → their contraction (formation of contraction cracks) → filling of contraction cracks with quartz, carbonates and ore minerals (crystallization from residual magmatic solutions mixed with formation waters). From this point of view it is syngenetic volcanogenic vein U-Mo-Cu mineralization, originally of the Permian age, with subsequent Alpine (most probably Cretaceous) reworking (this is evidenced by the variable composition of uraninite). It belongs to the Neohercynian late- to postorogenic metallogenetic stage. The possible younger, post-Permian age of mineralization from alpine hydrothermal solutions must also be assumed, but this consideration has several inconsistencies.

scholarly journals Petrographic and geochemical characteristics of the Nui Chua pegmatoid mafic-ultramafic series, Northern Vietnam: Significance in petrogenesis and Fe-Ti-V metallogenesis

2020 ◽  
Vol 43 (1) ◽  
pp. 80-94
Author(s):  
Pham Thi Dung ◽  
Tran Tuan Anh ◽  
Tran Quoc Hung ◽  
Tran Trong Hoa ◽  
R. A. Shelepaev ◽  
...  
Keyword(s):  
Rare Earth ◽  
Chemical Composition ◽  
Rare Earth Elements ◽  
Fractional Crystallization ◽  
Geochemical Characteristics ◽  
Ultramafic Rocks ◽  
Magma Source ◽  
Distribution Characteristics ◽  
Magmatic Origin ◽  
Northern Vietnam

The pegmatoid intrusions of the Nui Chua complex are one of the important mafic-ultramafic intrusive series associated with Fe-Ti-V ores in northern Vietnam. These intrusions consist of plagiowebsterite, clinopyroxenite, melanogabbronorite, mesogabbro, gabbronorite, and leucogabbronorite. The Fe-Ti oxide ores being massive or disseminated appear layered or veined in pegmatoid rocks. The geochemical characteristics of pegmatoid rocks are rich in Fe, Ti, V and poor Mg; their HREE are higher than LREE, with [La/Yb]N of 0.49 to 0.91 (average: 0.67), showing negative anomalies at Nb, Ta, Th, U, Sr, Zr and positive anomalies at Cs, Ti, and K. The chemical composition and distribution characteristics of trace and rare earth elements of mafic and ultramafic rocks show that they share the same magma source. Having the same geochemical tendency of intrusive formations, Fe-Ti oxide ores are magmatic origin associated with intrusive pegmatoid rocks. The pegmatoid rocks of the Nui Chua complex and Fe-Ti oxide ores are formed as a product of the fractional crystallization of Fe-Ti-rich residual melts after crystallization of the layered rocks.

scholarly journals Occurrence of Hardened Matters in the Andosolic Cover from the Western Highlands of Cameroon: Case Study of Those Risen on Trachyte in the Southern Side of the Bambouto Mountains

2019 ◽  
pp. 1-13
Author(s):  
J. C. Fopoussi Tuebue ◽  
S. D. Basga ◽  
P. Tematio ◽  
J. P. Nguetnkam
Keyword(s):  
Genetic Relationship ◽  
Geochemical Characteristics ◽  
Parent Rock ◽  
Ore Deposit ◽  
High Contribution ◽  
Southern Side

The aim of the present study is to acquire knowledge about the hardened materials present in the andosolic cover from the Bambouto Mounts. For that purpuse, petrographic, mineralogical, and geochemical characteristics of the hardened materials, isalteritic blocks, and the parent rock were investigated in order to put into relief the different facies found, the genetic relationship between those geological matters, and the mechanism governing the formation and the evolution of the hardened materials found in the Andosols from the Bambouto mounts. These matters have low thickness, are highly hardened, with different aspects and locations. They are present within the soils, at the point of emergence of streams, on the flatty areas on top of hills and at the foot of interfluves. Microscopically, their plasmas are respectively isotic and cristic. Gibbsite, goethite, and halloysite are respectively their main minerals. Geochemically, both facies are highly aluminous. During the weathering, Sanidine changes sequentially into Allophane, Halloysite, and Gibbsite; Pyroxen and Ilmenite for their own contribute to the formation of Goethite. There is a direct genetic relationship between the hardened materials, the isalteritic blocks, and the parent rock. The uphill position is the eluvial part and the downhill position the illuvial part; this generates the evolution of the hardened materials from their translucent initial status towards their reddening and tanning final status. The characteristics of the hardened materials make them bauxitic hardened materials, organized into two different facies: A lithorelictuel and a vitreous facies. The presence of those hardened materials in the Andosols from the Western Highlands of Cameroon is harmful for farming. The present study is then a high contribution to the management of the mine ore deposit within the Western Highlands of Cameroon.

scholarly journals Petrology, Geochemical Characteristics, Tectonic Setting, and Implications for Chromite and PGE Mineralization of the Hongshishan Alaskan-Type Complex in the Beishan Orogenic Collage, North West China

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhaolin Wang ◽  
Xiaoming Zheng ◽  
Guixiang Meng ◽  
Hejun Tang ◽  
Tonghui Fang
Keyword(s):  
Fractional Crystallization ◽  
Tectonic Setting ◽  
Orogenic Belt ◽  
Geochemical Characteristics ◽  
North West ◽  
The North ◽  
Light Yellow ◽  
Type Complex ◽  
Mafic Complex ◽  
Beishan Orogenic Collage

The Hongshishan mafic-ultramafic complex is situated in the north of the Beishan orogenic collage and the southern part of the Central Asian Orogenic Belt. This paper outlines the petrological, geochemical, and mineralogical data of the Hongshishan ultramafic–mafic complex in the Beishan orogenic collage to constrain its tectonic setting and mineralization. The lithological units of the complex include dunite, clinopyroxene peridotite, pyroxenite, and gabbro. The complex showed concentric zonation, from clinopyroxene peridotite and dunite in the core to pyroxenite and gabbro in the margin. These ultramafic–mafic rocks are characterized by cumulate and layering textures. Field observations, petrography, and significant elemental composition variation, a decreasing sequence of ferromagnesian minerals (Mg#), olivine Fo, and spinel Cr#, all show fractional crystallization trends from dunites through clinopyroxene peridotite and pyroxenite, to gabbros. There are systematic trends among the primary oxides, e.g., CaO, TiO2, and Al2O3, with MgO, suggesting a fractional crystallization trend. SiO2 and Al2O3 increased, which coupled with decreasing MgO, suggested olivine fractionation. The negative correlations of CaO and Al2O3 with MgO meant the accumulation of spinel and mafic minerals. The compositions of olivines from the dunite and clinopyroxene peridotite in the Hongshishan plot within the Alaskan Global trend fields displayed a typical fractional crystallization trend similar to olivines in an Alaskan-type complex. The clinopyroxenes in the clinopyroxene peridotite primarily occur as a diopside and appear in the field of an Alaskan-type complex. The absence of orthopyroxene, less hydrous, and free of fluid inclusions in the chrome spinels means the absence of a magmatic origin of chromite-bearing peridotites in hydrous parental melts or scarce hydrous melts. Serpentinization, carbonatization, subduction modification, and enrichment may account for the LILE-enrichment and HFSE-depletion of peridotite rocks. Negative Eu anomalies and REE fractionations of mafic-ultramafic rocks may not be directly attributed to crustal assimilation. Petrological, mineralogical, and geochemical characteristics indicated the Hongshishan complex is not the member compositions of a typical ophiolite. However, it displays many similarities to Alaskan-type mafic-ultramafic intrusions related to subduction or arc magmas setting at ∼366.1 Ma and suffered subduction modification and enrichment. The Hongshishan complex is a unique Ir-Ru-rich chromite deposit in the southern margin of the Altaids orogenic belt. Chromites occur primarily in light yellow dunites, with banded, lenticular, veined, thin-bedded, and brecciated textures. Part of the chromite enrichment in IPGE (Os, Ir, Ru) and the chondrite-normalized spider diagram of PGE showed steep right-facing sloped patterns similar to those of the PGE-rich ophiolitic chromites.

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