Numerical Simulation Based Targeting of the Magushan Skarn Cu-Mo Deposit, Middle-Lower Yangtze Metallogenic Belt, China

The Magushan Cu–Mo deposit is a skarn deposit within the Nanling–Xuancheng mining district of the Middle-Lower Yangtze River Metallogenic Belt (MLYRMB), China. This study presents the results of a new numerical simulation that models the ore-forming processes that generated the Magushan deposit and enables the identification of unexplored areas that have significant exploration potential under areas covered by thick sedimentary sequences that cannot be easily explored using traditional methods. This study outlines the practical value of numerical simulation in determining the processes that operate during mineral deposit formation and how this knowledge can be used to enhance exploration targeting in areas of known mineralization. Our simulation also links multiple subdisciplines such as heat transfer, pressure, fluid flow, chemical reactions, and material migration. Our simulation allows the modeling of the formation and distribution of garnet, a gangue mineral commonly found within skarn deposits (including within the Magushan deposit). The modeled distribution of garnet matches the distribution of known mineralization as well as delineating areas that may well contain high garnet abundances within and around a concealed intrusion, indicating this area should be considered a prospective target during future mineral exploration. Overall, our study indicates that this type of numerical simulation-based approach to prospectivity modeling is both effective and economical and should be considered an additional tool for future mineral exploration to reduce exploration risks when targeting mineralization in areas with thick and unprospective sedimentary cover sequences

The Lomagundi-Jatuli carbon isotopic event recorded in the marble of the Tandilia System basement, Río de la Plata Craton, Argentina

The “Lomagundi-Jatuli event” corresponds to the most important δ13C positive anomaly (≥5‰) globally reported in Palaeoproterozoic marine carbonates (between ∼2.30 and 2.06 Ga). In the Tandilia System (Argentina), Río de la Plata Craton, this event was recorded in the basement marble of the San Miguel area. The calcite-diopside marble, hosted by biotite gneiss and intruded by 2.12 Ga garnet-leucogranite, was metamorphosed in amphibolite facies during the Transamazonian Cycle. PAAS-normalised rare-earth elements (REE) and Y for the carbonate rocks are HREE-enriched and display positive Eu and Y anomalies, typical of primary precipitates from a mixed hydrothermal-marine environment carbonate. Additionally, a truly negative Ce anomaly for all the samples indicates that the depositional environment was oxidising. Positive δ13C values ranging from +5.90 to +4.30‰ (V-PDB), and δ18O from +17.45 to +13.84‰ (V-SMOW) were determined in this marble, both gradually decreasing towards the contact with the leucogranites. These values indicate that devolatilization reactions took place during the crystallisation of a wollastonite-vesuvianite-grossular-diopside skarn generated by the leucogranite intrusions into the marble. δ18O values obtained from diopside and calcite crystals, in the marble sectors furthest from the contacts with leucogranite, allowed a 663–623 °C formation temperature to be calculated, considering oxygen in a calcite-diopside geothermometric pair. These temperatures are consistent with the metamorphic degree (amphibolite facies) reached in this portion of the basement. Although the San Miguel marble shows petrographic and mineralogical evidence of regional and contact metamorphism, important geochemical and isotopic characteristics, together with its estimated Palaeoproterozoic age, indicate that the marble protolith was a marine carbonate deposited during the “Lomagundi-Jatuli event”.Fil: Lajoinie, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; ArgentinaFil: Lanfranchini, Mabel Elena. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; ArgentinaFil: Recio, C.. Universidad de Salamanca; EspañaFil: Sial, A.N.. Federal University of Pernambuco; BrasilFil: Cingolani, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Ballivian Justiniano, Carlos Alberto. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Etcheverry, Ricardo Oscar. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

Skarns in the Kamioka mine

The Kamioka mine, Gifu prefecture, working the largest lead and zinc deposit in Japan, lies in the eastern corner of the Hida gneiss complex. The skarn minerals in this mining district are genetically divided into the following three groups. Skarn A : Recrystallized skarn, formed by a regional metamorphism of impure limestone beds. The creation of skarn A is same in age to the formation of the Hida metamorphic complex. Skarn B : Zoned skarn along the contact between limestone and Inishi syenitic rock, having a same origination to Shimonomoto granite. The formation of skarn B is closely related to the intrusion of Shimonomoto granite. Skarn C : Pyrometasomatic skarn, formed by pyrometasomatic replacement of limestone probably after the deposition of the Mesozoic Tetori formation. The ore deposits of the Kamioka mine are composed of the pyrometasomatic skarn (skarn C) called "Mokuji" and the hydrothermal deposits called "Shiroji". Skarn A and skarn B have no genetical relation to the ore deposits. But skarn A acts the valuable role for the stratigrahical classification of ore deposits and limestone beds

Minerals in Afghanistan : the potential for copper

There are around 300 documented copper deposits, occurrences and showings in Afghanistan as shown in Figure 1. A variety of styles of copper mineralisation occur in rocks ranging in age from Proterozoic to Neogene. These include sediment-hosted, skarn, porphyry, and vein-hosted, as well as other types. The largest and best-known copper discovery in Afghanistan is the world-class Aynak stratabound deposit hosted within Vendian-Cambrian quartz-biotite-dolomite metasedimentary rocks 30 km south-south-east of Kabul. Soviet surveys in the 1970s and 1980s indicated resources of 240 Mt at 2.3 % Cu. However, Afghanistan has yet to be evaluated in the light of modern mineral deposit models and improved analytical methods. From a global perspective, Afghanistan is relatively under explored and the potential for further discoveries of copper and other minerals is high. A summary of the potential for copper in Afghanistan is shown in Table 1

Minerals in Afghanistan : the potential for gold

Gold has been worked in Afghanistan for centuries from many areas including Takhar province in the north and from Ghazni, Zabul, and Kandahar provinces in the south-west of the country. Currently, gold is produced almost solely by artisanal miners working the Samti Placer Deposit in Takhar Province. Gold deposits and prospects are known in rocks of Proterozoic to Neogene age. Many styles of gold mineralisation occur, in particular skarn, vein-hosted, porphyry and alluvial. Afghanistan is relatively under-explored and has not yet been evaluated in the light of modern mineral deposit models and using up-to-date sophisticated analytical methods and exploration techniques. There is significant potential for further discoveries of gold mineralisation throughout the country in a variety of styles especially porphyry Cu-Au and skarn Cu-Au

The use of ERTS-1 images in the search for large sulfide deposits in the Chagai District, Pakistan

The author has identified the following significant results. Visual examination of color composites was tested under relatively ideal conditions for direct detection of large hydrothermal sulfide deposits at the low-grade porphyry copper deposit at Saindak, western Chagai District, Pakistan. The Saindak deposit is characterized by an elongate zone of easily eroded sulfide-rich rock surrounded by a resistant rim of hornfels and propylitically altered rock. The geomorphic features related to the Saindak deposit are easily distinguished on ERTS-1 images. Attempts to detect a color anomaly using false-color composites were not successful. About 36,000 square km of the western Chagai District were examined on false-color composites for direct evidence of large sulfide deposits. New geologic information acquired from the images was used in conjunction with the known geology to evaluate two previously known proposed areas and to suggest seven additional targets for field checking, one of which is proposed on the basis of tonal anomaly alone. The study also showed that Saindak-type deposits are not likely to be present in some extensive areas of the Chagai District; and also that a rim like that at Saindak does not form if regional metamorphism has increased the resistance of the country rock to erosion

A Comparative Study of the Mineralogy and Petrology of the Mazraeh Cu-Fe Skarn Deposit, Iran and the Cu-Fe Skarn Deposit in the Edong Ore District, China

Cu and Fe skarn deposits are some of the largest skarn deposits that are important for various important elements. There are exhaustive reviews of the Cu and Fe skarn deposits, but the characteristics of Cu-Fe skarn deposit are poorly explained. This thesis evaluates previous review papers concerning the Cu-Fe skarn deposits at two different geologic settings: the Mazraeh Cu-Fe skarn deposit in Iran and the Cu-Fe skarn deposit in the Edong ore district, China. These Cu-Fe skarn deposits are among the largest and most important Cu-Fe skarn deposits. Compared to Cu and Fe skarn deposits, this deposit type also consists of gold as a by-product. This thesis also summarizes the tectonic setting and petrogenesis of Cu-Fe skarn deposits and examines the petrology and mineralogy of Cu-Fe skarn deposits. This thesis focuses on studying the mineral assemblages, the ternary plots, the end-member minerals, and the thin sections of each skarn deposit for comparisons and interpretations. Prograde skarn minerals, specifically garnet and pyroxene share similar compositions in both skarn deposits. Both skarn deposits have andraditic garnet and diopsidic pyroxene. For the Mazraeh Cu-Fe skarn deposit, the endoskarn contains the red-brown andradite with composition of 45.08– 68.33 mol% andradite, 19.05–39.34 mol% grossular, and 4.52–12.33 mol% almandine. The exoskarn contains the green-yellow grossular garnet that consists of 64.25–78.88 mol% grossular, 8.77– 20.55 mol% andradite, and 7.51–11.49 mol% almandine. The pyroxene is diopside-rich. The Cu-Fe skarn deposit in the Edong ore district contains 29-95 mol% andradite and 0-68 mol% grossular. The pyroxene is also diopside rich with 54-98 mol% diopside and 2-45 mol% hedenbergite. Petrological evidence shows that the prograde minerals are replaced by the retrograde minerals, including important ore minerals for Cu and Fe such as chalcopyrite, pyrite, and hematite. Both deposits have well-developed exoskarn and endoskarn system, with exoskarn containing more Cu and Fe mineralization, suggesting similar characteristics of Cu-Fe skarn deposits in the Mazraeh district, Iran and the Edong ore district, China.No embarg

Petrological Conditions Associated with Gold Deposition at Browns Creek Skarn, Australia

Browns Creek is a skarn that hosts an Au-Cu ore deposit in the Blayney region of New South Wales, Australia. Skarn rock at this location is wollastonite marble, highly mineralized by sulfides and gold deposited as native Au, electrum, telluride minerals and within arsenopyrite crystals. Related alteration includes metasomatized hornfels of the Ordovician Blayney Volcanics and marbleized interbedded limestone lenses of the Cowriga Limestone Member. Magmatic fluids responsible for this alteration were derived from a Silurian felsic-intermediate multi-phase intrusive system, the Browns Creek Intrusive Complex. Main constituents of this intrusive system include the Carcaor Granodiorite, the first and largest phase responsible for main pluton emplacement and skarnification of country rock, and the Mine Dyke Group, which is a smaller and more felsic phase attributed to carrying the ore-bearing fluids deposited at Browns Creek. As a small mine that is no longer operational, Browns Creek offers an example of an economic deposit that has not been thoroughly studied. This honors thesis aims to use petrological and geochemical analyses to better understand the conditions associated with gold deposition at Browns Creek by focusing on host rocks and metallic minerals deposited outside of the primary ore zone. polished blocks and thin sections were prepared for petrographic and microprobe analysis in order to more fully comprehend mineralogical processes occurring here, and supporting evidence was found for striking results presented by the most recent study on this site. These results include the assignment of Browns Creek as a skarn-hosted ore deposit resulting from a magmatic event post-alteration rather than a true skarn deposit, in addition to the re-dating of Browns Creek Intrusive Complex—presenting a Silurian age ~15Ma older than previously understood. These notable distinctions are investigated here through different approaches than previously explored. Additionally, links are proposed between Browns Creek deposit characteristics and tectonic regime, assigning primary Au-Cu ore deposition to a Silurian volcanic arc environment while suggesting that anomalously occurring Sn mineralization is the result of a later Devonian event within a rifting environment

Mineral zoning and gold occurrence in the Fortuna skarn mine, Nambija district, Ecuador

The Fortuna oxidized gold skarn deposit is located in the northern part of the Nambija gold district, southern Ecuador. It has been subdivided into four mineralized sites, covering a distance of 1km, which are named from north to south: Cuerpo 3, Mine 1, Mine 2, and Southern Sector. Massive skarn bodies occur in K-Na metasomatized volcanic and volcaniclastic rocks of the Triassic Piuntza unit. They appear to result from selective replacement of volcaniclastic rocks. Very minor presence of bioclast relicts suggests the presence of subordinate limestone. Endoskarn type alteration with development of Na-rich plagioclase, K-feldspar, epidote, actinolite, anhedral pyroxene, and titanite affects a quartz-diorite porphyritic intrusion which crops out below the skarn bodies in Mine 2 and the Southern Sector. Endoskarn alteration in the intrusion grades into a K-feldspar ± biotite ± magnetite assemblage (K-alteration), suggesting that skarn formation is directly related to the quartz-diorite porphyritic intrusion, the latter being probably emplaced between 141 and 146Ma. The massive skarn bodies were subdivided into a dominant brown garnet skarn, a distal green pyroxene-epidote skarn, and two quartz-rich varieties, a blue-green garnet skarn and light green pyroxene-garnet skarn, which occur as patches and small bodies within the former skarn types. The proximal massive brown garnet skarn zone is centered on two 060° trending faults in Mine 2, where the highest gold grades (5-10g/t) were observed. It grades into a distal green pyroxene-epidote skarn zone to the North (Cuerpo 3). Granditic garnet shows iron enrichment from the proximal to the distal zone. Diopsidic pyroxene exhibits iron and manganese enrichment from proximal to distal zones. The retrograde stage is weakly developed and consists mainly of mineral phases filling centimeter-wide veins, vugs, and interstices between garnet and pyroxene grains. The main filling mineral is quartz, followed by K-feldspar, epidote, calcite, and chlorite, with minor sericite, apatite, titanite, hematite, pyrite, chalcopyrite, and gold. Metal and sulfur contents are low at Fortuna, and the highest gold grades coincide with high hematite abundance, which suggests that retrograde stage and gold deposition took place under oxidizing conditions. Fluid inclusions from pyroxene indicate precipitation from high temperature—high to moderate salinity fluids (400 to 460°C and 54- to 13-wt% eq. NaCl), which result probably from boiling of a moderately saline (∼8-wt% eq. NaCl) magmatic fluid. Later cooler (180 to 475°C) and moderate to low saline fluids (1- to 20-wt% eq. NaCl) were trapped in garnet, epidote, and quartz, and are interpreted to be responsible for gold deposition. Chlorite analysis indicates temperature of formation between 300 and 340°C in accordance with fluid inclusion data. It appears, thus, that gold was transported as chloride complexes under oxidizing conditions and was deposited at temperatures around 300°C when transport of chloride complexes as gold carriers is not efficien