Geologic and Isotopic Constraints on the Age and Origin of Auriferous Quartz Veins in the Parcoy Mining District, Pataz, Perú

1999 ◽  
Author(s):  
Andrew W. Macfarlane ◽  
Richard M. Tosdal ◽  
César E. Vidal ◽  
Jorge Paredes
Keyword(s):  
Mining District ◽  
Quartz Veins ◽  
Isotopic Constraints

Petrogenesis of amphibole – biotite – calcite – plagioclase alteration and laminated gold – silver quartz veins in four Archean shear zones of the Norseman district, Western Australia

1992 ◽  
Vol 29 (3) ◽  
pp. 388-417 ◽  
Author(s):  
Andreas G. Mueller
Keyword(s):  
Western Australia ◽  
Shear Zones ◽  
Wall Rock ◽  
Alteration Zone ◽  
Mining District ◽  
Low Grade ◽  
Fluid Temperature ◽  
Quartz Veins ◽  
The North ◽  
Gold Silver

The Norseman mining district in the Archean Yilgarn Block, Western Australia, has produced 140 t of gold and about 90 t of silver from 11.24 × 106 t of ore. The district is located within a metamorphic terrane of mafic and minor ultramafic greenstones, intruded by granite cupolas and swarms of porphyry dykes. The orebodies consist of laminated quartz veins, controlled by narrow (0.5–5 m) reverse shear zones that, in general, follow the contacts of metapyroxenite or porphyry dykes. Petrological studies of four shear zones, exposed on the Regent shaft 14 level, Ajax shaft 10 level, and in the stope above the North Royal shaft 5 level, show that the host rocks were metamorphosed to hornblende–plagioclase amphibolites and actinolite–chlorite rocks at temperatures of 500–550 °C prior to mineralization.At the localities studied, intense wall-rock replacement and low-grade (0.5 g/t) gold mineralization are confined to ductile or brittle–ductile shear structures. Alteration is similar in both ultramafic and mafic greenstones, and consists of an inner zone of biotite–quartz–calcite–plagioclase rock with minor actinolitic hornblende and quartz–calcite–actinolite veinlets, and an outer zone, locally developed, of chlorite–calcite–quartz rock. At an estimated pressure of 3 kbar (300 MPa), fluid temperatures during wall-rock alteration are constrained by the hydrothermal mineral assemblages to 480 ± 30 °C in two shear zones on the Regent shaft 14 level, and to 450 ± 20 °C in one shear zone in the North Royal shaft 5 level stope. The mole fraction of CO2 of the fluids is estimated at [Formula: see text], and the sulphur fugacity at 10−6 bar (10−1 kPa) (at 450 °C), based on the assemblage pyrrhotite + pyrite ± arsenopyrite. The development of an outer chloritic alteration zone at North Royal is related to the lower fluid temperature at this locality.High-grade (up to 75 g/t Au, 283 g/t Ag) veins formed within three of the shear zones studied at fluid temperatures of 400 °C and less, by the successive accretion of quartz laminae, separated by films of retrograde chlorite and sericite. The assemblage of ore minerals in the veins differs from that in the altered wall rocks, and includes disseminated galena, Pb–Bi–Ag tellurides, and native gold, which coprecipitated with the quartz. The orebodies at Norseman show affinities to Phanerozoic and Archean gold skarn deposits.

scholarly journals Mineral chemistry of In-bearing minerals in the Santa Fe mining district, Bolivia

2018 ◽  
Vol 45 (3) ◽  
pp. 410 ◽  
Author(s):  
Abigail Jiménez-Franco ◽  
Pura Alfonso ◽  
Carles Canet ◽  
Juan Elvys Trujillo
Keyword(s):  
Mineral Chemistry ◽  
Point Of View ◽  
Igneous Rocks ◽  
Mining District ◽  
Critical Element ◽  
Santa Fe ◽  
Economic Point ◽  
Quartz Veins ◽  
Mineral Phases ◽  
High Concentrations

The Santa Fe mining district is located in the Central Andean tin belt of Bolivia and contains several Sn-Zn-Pb-Ag deposits. From the economic point of view, the most important deposits of the district are Japo, Santa Fe and Morococala. Beyond the traditional metal commodities, the Central Andean Tin Belt could become an exploration target for indium, owing to the potential of the ore-bearing paragenesis with high concentrations of this technology-critical element. In the Santa Fe mining district, the ore occurs as two main types: (a) Sn-rich cassiterite-quartz veins, and (b) Zn-Pb-Ag veins with sphalerite, galena and stannite mineral phases. The In content in igneous rocks is between 1.5 and 2.5 ppm, whereas in the ore concentrate it attains up to 200 ppm. The 1,000×In/Zn ratio in concentrate ranges from 25 up to 4,000. Exceptionally high In values were found in sakuraiite from Morococala deposit (2.03 wt%). Sakuraiite in this deposit shows evidences for a link between stannite and kësterite trend of solid solutions. There is a noteworthy exploration potential for strategic metals in this district and even in similar deposits elsewhere in the Central Andean tin belt.

Preliminary petrographic study of dolerites related to Sb-Au mineralizations: example of Ribeiro da Serra mine (Dúrico-Beirão mining district, NW Portugal) 

2021 ◽  
Author(s):  
Rui Frutuoso ◽  
Maria dos Anjos Ribeiro ◽  
Alexandre Lima ◽  
Helena Sant'Ovaia
Keyword(s):  
Spatial Relationship ◽  
Shear Zones ◽  
Geochemical Data ◽  
Mining District ◽  
Petrographic Composition ◽  
Metasedimentary Rocks ◽  
Quartz Veins ◽  
Accessory Phase ◽  
Variscan Granites ◽  
Petrographic Study

<p>In the Dúrico-Beirão mining district, several occurrences of Sb-Au are known, which were exploited since the Roman occupation in Iberia until mid-last century. This region is located in the Central Iberian Zone of the Iberian Massif, part of the Ibero-Armorican Arc. The country rocks in the area consist of folded metasedimentary rocks from Cambrian to Carboniferous surrounded by syn- to post-orogenic Variscan granites. The Ribeiro da Serra Sb-Au mine, intensively exploited in the 19<sup>th</sup> century, occurs west of the western limb of the Valongo Anticline, a major ante-Stephanian structure with NW-SE trend. This Sb-Au deposit consist mainly of stibnite-bearing quartz veins hosted by slates, quartzites and conglomerates of the Schist-Greywacke Complex in a possible spatial relationship with dolerite dykes. These mafic dykes are emplaced in sub-parallel shear zones to the sinistral Douro Shear Zone and their presence may suggest the existence of mafic/ultramafic bodies at depth, which contributed to the occurrence of Sb-Au deposits.</p><p>This study aims to describe the dolerite dykes present through the region (petrographic composition, weathering, distribution, and dimension) considering a possible contribution for the Sb-Au occurrence. Dolerites are greyish-green colored and are intensely weathered. The samples surface shows a few millimeters of brownish supergenic alteration. The petrographic study highlighted an intense chloritization and saussuritization of plagioclase, whose tabular form and twinning are still preserved. The primary igneous texture is better preserved than the primary mineralogy. The texture is ophitic to sub-ophitic although the interstitial mass of the pyroxene is totally altered.  Chlorites occur as fresh, green-colored patches, sometimes with radiated fibrous textures. Frequent polycrystalline quartz lenses and veins occur, also as consequence of the hydrothermal/metamorphic alteration. The opaques, not yet identified, occur in a great modal percentage, and are frequently associated with titanite. They do not seem to have a special concentration related to quartz veins and lenses. Apatite is a frequent accessory phase and appears to be preferentially associated with opaque minerals.</p><p>The knowledge of the petrographic characteristics of these dolerite dykes, associated with geochemical data, can be a great contribution to the understanding of the distribution of Sb mineralization and corroborate the hypothesis of non-outcropping mafic/ultramafic bodies.</p><p> </p><p><strong>Acknowledgment</strong></p><p>The work was financial supported within the compass of the ERA-MIN/0005/2018—AUREOLE project, FEDER through operation POCI-01-0145-FEDER-007690 funded by the Programa Operacional Competitividade Internacionalização—COMPETE2020 and by National Funds through FCT within the ICT (reference UIDB/04683/2020).</p>

Cretaceous reduced granitoids in the Goodpaster Mining District, east central Alaska

2007 ◽  
Vol 44 (9) ◽  
pp. 1347-1373 ◽  
Author(s):  
Katherine M Dilworth ◽  
James K Mortensen ◽  
Shane Ebert ◽  
Richard M Tosdal ◽  
Moira T Smith ◽  
...  
Keyword(s):  
Crustal Thickening ◽  
Mining District ◽  
Limited Data ◽  
Calc Alkaline ◽  
High Field Strength ◽  
Peraluminous Granite ◽  
East Central ◽  
Quartz Veins ◽  
Granitoid Emplacement ◽  
Granite Suite

The >5 Moz (1 oz (troy) = 31.103 g) gold veins of the Liese Zone and nearby prospects in the Goodpaster Mining District of east central Alaska are spatially and temporally associated with late-Early to Late Cretaceous reduced granitoids that are divided into a granite suite, tonalite suite, and diorite suite in decreasing age. Synkinematic to postkinematic biotite ± hornblende granite, granodiorite, pegmatite, and two-mica granite with accessory garnet compose the granite suite (109–107 Ma). The tonalite suite (107–103 Ma) forms small to large bodies of postkinematic hornblende–biotite granodiorite to tonalite with rare granite. Intruding the granite and parts of the tonalite suites are aplite and pegmatite that grade through sugary pegmatoidal or aplitic quartz veins and finally into quartz veins along strike. The diorite suite (95.4–93.7 Ma) consists of small stocks of diorite to tonalite that intrude the older suites and are inferred to intrude the shallowly dipping auriferous quartz veins. Limited data indicate granitoid emplacement at 5–9 km depths, consistent with formation of the auriferous quartz veins based upon published fluid inclusion data. The weakly peraluminous granite and tonalite suites are distinguished by variable amounts of monazite and zircon whereas the diorite suite is metaluminous, contains <5% magnetite, and lacks monazite. All suites are subalkalic, calc-alkaline and have low magnetic susceptibilities, high large-ion lithophile element/high field-strength element (LILE/HFSE), and depleted Nb and Ti. The granite suite has higher 206Pb/204Pb values (19.4–19.6) than the diorite (19.1). Overall the granite and tonalite suites likely represent melts generated late during crustal thickening that intruded along shallowly dipping faults during exhumation, whereas the diorite suite represents postdeformation melts that underwent less interaction with the old silicic crust.

scholarly journals Fluid Inclusion Study of Epithermal Gold-Base Metal Mineralization System in the Shwebontha Prospect, Monywa Mining District, Central Myanmar Monywa

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Toe Naing Oo ◽  
Agung Harijoko ◽  
Lucas Donny Setijadji ◽  
Kotaro YONEZU
Keyword(s):  
Fluid Inclusion ◽  
Base Metal ◽  
Homogenization Temperature ◽  
Hydrothermal Fluids ◽  
Fluid Inclusion Study ◽  
Mining District ◽  
Quartz Veins ◽  
Ore Mineralization ◽  
Inclusion Study ◽  
Gold Bearing

The Shwebontha Prospect area is one of prominent epithermal Au-Ag prospects in Monywa mining district, central Myanmar, characterized by the appearance of gold-bearing and base metal quartz veins with gold grade is around 3g/t -10.4g/t. The geology of the area consists of the volcanic and volcaniclastic rocks of Upper Oligocene-Middle Miocene Magyigon Formation that served as the host rock of the ore mineralization. This research focused on fluid inclusion study is aimed to know the characteristics of hydrothermal fluids during ore mineralization as well as the possible paleo- depth and temperature of formation of gold-bearing and base metal quartz veins. The mineralization styles are gold-bearing brecciated quartz veins and chalcedonic quartz veins where sulfides are clustered as well as disseminated both in quartz gangue and volcanic host rocks. Those quartz veins include pyrite, sphalerite, galena, chalcopyrite and gold (electrum). Fluid inclusion microthermometry indicates that the ore mineralization is characterized by the values of homogenization temperature range from 158°C to 310°C and salinities range from 0.35 to 2.41wt.% NaCl equiv. This temperature is consistent with the formation temperature of 250°C to 270 °C and also their estimate paleo-depth of formation is between 440m and 640m respectively. Microthermometric data indicates that fluid mixing and dilution were significant processes during ore mineralization and evolution of hydrothermal fluids. Based on the petrography of fluid inclusion, microthermometric measurements and ore minerals assemblage as well as estimation of paleo-depth from the Shwebontha Prospect imply that forming in under shallow level epithermal environment

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