scholarly journals LITHOSTRATIGRAPHIC CONTROL OF THE CANGAS-POCONÉ LINEAMENT AURIFEROUS DEPOSITS (PARAGUAY BELT): IMPLICATIONS FOR REGIONAL EXPLORATION

2019 ◽  
Vol 4 (4) ◽  
pp. 501-517
Author(s):  
Raíza De Sousa Batalha ◽  
Elzio Da Silva Barboza ◽  
Carlos Humberto ◽  
Cláudia Do Couto Tokashiki ◽  
Francisco Egídio Cavalcante Pinho ◽  
...  
Keyword(s):  
Gold Mineralization ◽  
Low Permeability ◽  
Fluid Migration ◽  
Gold Concentration ◽  
High Angle ◽  
Migration Path ◽  
Quartz Veins ◽  
Gold Exploration ◽  
Preferential Location ◽  
Host Rocks

rocks of the Cuiaba Group, into the inner portion of the Paraguay Belt (Brazil). They occur in a belt (~1200 m) where the host rocks are graphitic phyllites, metadiamictites, metasiltites and sandstones metamorphosed in greenschist facies. In these deposits gold occurs free or included in pyrite related to three types of quartz veins, parallel to Sn (V1), parallel to Sn+1 (V2) and orthogonal (V3) which are rich in gold. The study of outcrops in regional profiles, open mines for gold exploration and drilling holes in the Cangas-Poconé alignment indicate that the preferential location of gold mineralization at (Cangas Facies) is related to the existence of strong lithological control of the mineralizations.The Cangas facies present low permeability of rhythmite, structural arrangement of permeability barriers S0 and S1 at high angle with respect to the fluid migration path and mainly the presence of ferruginous levels acting as geochemical barriers for precipitation of metals in solution in the fluid. The knowledge that gold concentration is related to sedimentary control is important for regional exploration and is a guide for local miners. CONTROLE LITOSTRATIGRÁFICO DOS DEPÓSITOS AURÍFEROS DO LINEAMENTO CANGAS-POCONÉ (CINTURÃO PARAGUAI): IMPLICAÇÕES PARA A EXPLORAÇÃO REGIONAL ResumoOs depósitos de Cangas-Poconé estão hospedados em rochas metassedimentares do Grupo Cuiabá, na porção interna do Cinturão do Paraguai (Brasil). Eles ocorrem em um cinturão (~ 1200 m), onde as rochas hospedeiras são filitos, metadiamictitos, metasiltitos e arenitos grafitados, metamorfoseados em fácies de xisto verde. Nesses depósitos, o ouro ocorre livre ou incluído em pirita relacionada a três tipos de veios de quartzo. O estudo de afloramentos em perfis regionais, minas abertas para exploração de ouro e perfurações no alinhamento Cangas-Poconé indica que a localização preferencial da mineralização de ouro em (Cangas Facies) está relacionada à existência de forte controle litológico.O conhecimento de que a mineralização de ouro está relacionada ao controle sedimentar é importante para a exploração regional e é um guia para os mineradores locais. Palavras-chave: Ouro. Controle Sedimentar. Grupo Cuiabá. Cinturão do Paraguai.

scholarly journals Karakteristik Fluida Hidrotermal Endapan Emas Orogenik di Pegunungan Rumbia, Kabupaten Bombana, Provinsi Sulawesi Tenggara

2019 ◽  
Vol 20 (2) ◽  
pp. 111
Author(s):  
Hasria Hasria ◽  
Arifudin Idrus ◽  
I Wayan Warmada
Keyword(s):  
First Generation ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Salinity Range ◽  
Quartz Veins ◽  
The Third ◽  
Orogenic Gold Deposits ◽  
Gold Exploration ◽  
Calcite Veins

Recently, gold exploration activities  are not only focused along volcanic-magmatic belt but also starting to shift along metamorphicand sedimentary terrains. The purpose of this study is to analyses the characteristics hydrothermal fluids gold deposits t in the Rumbia Mountains, Bombana Regency, Southeast Sulawesi. There are three generations of veins identified including the first is parallel to the foliations, the second crosscuts the first generation of veins/foliations, and the third is of laminated deformed quartz+calcite veins at the late stage. Temperature of homogenization (Th) and salinity at Rumbia Mountain of the first vein vary from 220 to 355.30oC and 6.74 to 10.11 wt. % NaCl eq., respectively. The second generation vein was originated at Th of 157 to 255.50oC and salinity of 3.39 to 6.88 wt.%NaCl eq., whereas the third generation vein formed at lowest Th varying from 104.40 to 265.90oC and less saline fluid at salinity range between 0.18 and 6.30 wt.% NaCl eq. The result of temperature formation value correlation to the depth of the formation of orogenic gold deposits in Rumbia Mountain is indicated to form on sub-greenschist to greenschist facies at depth of about 4-8 kilometers and formation temperature between 104.40 - 355.30oC at zone epizonal and mesozonal. Based on characteristics fluids inclusion discussed above, the primary metamorphic-hosted gold mineralization type at Rumbia Mountain tends to meet the criteria of orogenic gold type.  Keyword : fluid iclusion, quartz veins, Rumbia mountain, orogenic gold deposits.

scholarly journals Metamorphic rock-hosted orogenic gold deposit style at Bombana (Southeast Sulawesi) and Buru Island (Maluku): Their key features and significances for gold exploration in Eastern Indonesia

2017 ◽  
Vol 2 (2) ◽  
pp. 124 ◽  
Author(s):  
Arifudin Idrus ◽  
Sukamandaru Prihatmoko ◽  
Ernowo Harjanto ◽  
Franz Michael Meyer ◽  
Irzal Nur ◽  
...  
Keyword(s):  
Fluid Inclusions ◽  
Metamorphic Rock ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
High Grade ◽  
Quartz Veins ◽  
Gold Exploration ◽  
Eastern Indonesia ◽  
Key Features ◽  
Gold Bearing

In Indonesia, gold is commonly mined from epithermal-, porphyry-, and skarn-type deposits that are commonly found in volcanic belts along island arcs or active continental margin settings. Numerous gold prospects, however, were recently discovered in association with metamorphic rocks. This paper focuses on metamorphic rock-hosted gold mineralization in Eastern Indonesia, in particular the Bombana (SE Sulawesi) and Buru Island (Maluku) prospects. At Bombana, gold-bearing quartz-veins are hosted by the Pompangeo metamorphic complex. Sheared, segmented veins vary in thickness from 2 cm to 2 m. Gold is mainly present in the form of ‘free gold’ among silicate minerals and closely related to cinnabar, stibnite, tripuhyite, and in places, minor arsenopyrite. The gold distribution is erratic, however, ranging from below detection limit up to 134 g/t. At least three generations of veins are identified. The first is parallel to the foliation, the second crosscuts the first generation of veins as well as the foliation, and the late-stage laminated deformed quartz-calcite vein represents the third mineralization stage. The early veins are mostly massive to crystalline, occasionally brecciated, and sigmoidal, whereas the second-stage veins are narrower than the first ones and less subjected to brecciation. Gold grades in the second- and third-stage veins are on average higher than that in the earlier veins. Microthermometric and Raman spectrometric studies of fluid inclusions indicate abundant H2O-NaCl and minor H2O-NaCl-CO2 fluids. Homogenization temperatures and salinities vary from 114 to 283 ºC and 0.35 to 9.08 wt.% NaCl eq., respectively. Crush-leach analysis of fluid inclusions suggests that the halogen fluid chemistry is not identical to sea water, magmatic or epithermal related fluids, but tends to be similar to fluids in mesothermal-type gold deposits. In Buru Island (Gunung Botak and Gogorea prospects), two distinct generations of quartz veins are identified. Early quartz veins are segmented, sigmoidal discontinuous and parallel to the foliation of the host rock. This generation of quartz veins is characterized by crystalline relatively clear quartz, and weakly mineralized with low sulfide and gold contents. The second type of quartz veins occurs within the ‘mineralized zone’ of about 100 m in width and ~1,000 m in length. Gold mineralization is intensely overprinted by argillic alteration. The mineralization-alteration zone is probably parallel to the mica schist foliation and strongly controlled by N-S or NE-SW-trending structures. Gold-bearing quartz veins are characterized by banded texture particularly following host rock foliation and sulphide banding, brecciated and rare bladed-like texture. Alteration types consist of propylitic (chlorite, calcite, sericite), argillic and carbonation represented by graphite banding and carbon flakes. Ore mineral comprises pyrite, native gold, pyrrhotite, and arsenopyrite. Cinnabar and stibnite are present in association with gold. Ore chemistry indicates that 11 out of 15 samples yielded more than 1 g/t Au, in which 6 of them graded in excess of 3 g/t Au. All high-grade samples are composed of limonite or partly contain limonitic material. This suggests the process of supergene enrichment. Interestingly, most of the high-grade samples contain also high concentrations of As (up to 991ppm), Sb (up to 885ppm), and Hg (up to 75ppm). Fluid inclusions in both quartz vein types consist of 4 phases including L-rich, V-rich, L-V-rich and L1-L2-V (CO2)-rich phases. The mineralizing hydrothermal fluid typically is CO2-rich, of moderate temperature (300-400 ºC), and low salinity (0.36 to 0.54 wt.% NaCl eq). Based on those key features, gold mineralization in Bombana and Buru Island tends to meet the characteristics of orogenic, mesothermal types of gold deposit. Metamorphic rock-hosted gold deposits could represent the new targets for gold exploration particularly in Eastern Indonesia.

scholarly journals Karakteristik Fluida Hidrotermal Endapan Emas Orogenik di Pegunungan Rumbia, Kabupaten Bombana, Provinsi Sulawesi Tenggara

2019 ◽  
Vol 20 (2) ◽  
pp. 111
Author(s):  
Hasria Hasria ◽  
Arifudin Idrus ◽  
I Wayan Warmada
Keyword(s):  
First Generation ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Salinity Range ◽  
Quartz Veins ◽  
The Third ◽  
Orogenic Gold Deposits ◽  
Gold Exploration ◽  
Calcite Veins

Recently, gold exploration activities  are not only focused along volcanic-magmatic belt but also starting to shift along metamorphicand sedimentary terrains. The purpose of this study is to analyses the characteristics hydrothermal fluids gold deposits t in the Rumbia Mountains, Bombana Regency, Southeast Sulawesi. There are three generations of veins identified including the first is parallel to the foliations, the second crosscuts the first generation of veins/foliations, and the third is of laminated deformed quartz+calcite veins at the late stage. Temperature of homogenization (Th) and salinity at Rumbia Mountain of the first vein vary from 220 to 355.30oC and 6.74 to 10.11 wt. % NaCl eq., respectively. The second generation vein was originated at Th of 157 to 255.50oC and salinity of 3.39 to 6.88 wt.%NaCl eq., whereas the third generation vein formed at lowest Th varying from 104.40 to 265.90oC and less saline fluid at salinity range between 0.18 and 6.30 wt.% NaCl eq. The result of temperature formation value correlation to the depth of the formation of orogenic gold deposits in Rumbia Mountain is indicated to form on sub-greenschist to greenschist facies at depth of about 4-8 kilometers and formation temperature between 104.40 - 355.30oC at zone epizonal and mesozonal. Based on characteristics fluids inclusion discussed above, the primary metamorphic-hosted gold mineralization type at Rumbia Mountain tends to meet the criteria of orogenic gold type.  Keyword : fluid iclusion, quartz veins, Rumbia mountain, orogenic gold deposits.

scholarly journals Karakteristik Fluida Hidrotermal Endapan Emas Orogenik di Pegunungan Rumbia, Kabupaten Bombana, Provinsi Sulawesi Tenggara

2019 ◽  
Vol 20 (2) ◽  
pp. 111
Author(s):  
Hasria Hasria ◽  
Arifudin Idrus ◽  
I Wayan Warmada
Keyword(s):  
First Generation ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Salinity Range ◽  
Quartz Veins ◽  
The Third ◽  
Orogenic Gold Deposits ◽  
Gold Exploration ◽  
Calcite Veins

Recently, gold exploration activities  are not only focused along volcanic-magmatic belt but also starting to shift along metamorphicand sedimentary terrains. The purpose of this study is to analyses the characteristics hydrothermal fluids gold deposits t in the Rumbia Mountains, Bombana Regency, Southeast Sulawesi. There are three generations of veins identified including the first is parallel to the foliations, the second crosscuts the first generation of veins/foliations, and the third is of laminated deformed quartz+calcite veins at the late stage. Temperature of homogenization (Th) and salinity at Rumbia Mountain of the first vein vary from 220 to 355.30oC and 6.74 to 10.11 wt. % NaCl eq., respectively. The second generation vein was originated at Th of 157 to 255.50oC and salinity of 3.39 to 6.88 wt.%NaCl eq., whereas the third generation vein formed at lowest Th varying from 104.40 to 265.90oC and less saline fluid at salinity range between 0.18 and 6.30 wt.% NaCl eq. The result of temperature formation value correlation to the depth of the formation of orogenic gold deposits in Rumbia Mountain is indicated to form on sub-greenschist to greenschist facies at depth of about 4-8 kilometers and formation temperature between 104.40 - 355.30oC at zone epizonal and mesozonal. Based on characteristics fluids inclusion discussed above, the primary metamorphic-hosted gold mineralization type at Rumbia Mountain tends to meet the criteria of orogenic gold type.  Keyword : fluid iclusion, quartz veins, Rumbia mountain, orogenic gold deposits.

scholarly journals Gold composition and conditions of Southern Ak-Dag gold-sulfide-quartz ore occurrence formation (Western Tuva)

LITOSFERA ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 706-716
Author(s):  
N. N. Ankusheva ◽  
R. V. Kuzhuget
Keyword(s):  
Fluid Inclusion ◽  
Gold Mineralization ◽  
Ore Deposits ◽  
High Rate ◽  
High Grade ◽  
Mineral Formation ◽  
Quartz Veins ◽  
Ore Mineralization ◽  
Host Rocks ◽  
Gold Sulfide

Research subject. The paper presents data on the mineralogical, geochemical and fluid inclusion features of the Southern Ak-Dag gold-sulphide-quartz ore occurrence in Western Tuva.Methods. Mineral formation temperatures, salt composition and fluid salinity were examined using a Linkam TMS-600 cryostage and an Olympus BX 51 microscope. The chemical composition of samples was identified using a MIRA 3 LMU (Tescan Orsay Holding) scanning electron microscope equipped with INCA Energy 450+XMax 80 and INCA Wave 500 microanalysis systems; BSE photos were taken by Tescan Vega 3 and Hitachi ТМ-1000 SEM instruments.Results. The ores under study were found to contain both high-grade and medium-grade gold with an Ag content of up to 17.05 wt %. The average gold fineness comprised 904 ‰, ranging from 830 to 928 ‰. According to fluid inclusion data, gold-sulphide-quartz veins were formed at temperatures of 280–240 °C and pressures of 0.8–1.2 kbar from aqueous fluids having a salinity of 8.6–6.4 wt % NaCl eq. The narrow range of fluid salinity at decreasing temperatures and the prevalence of high-grade gold in sulphide-quartz veins indicate a relatively high rate of mineral formation in a narrow permeable zone without any significant interaction with host rocks or mixing with meteoric waters.Conclusions. Gold mineralization in the Southern Ak-Dag ore occurrence, which was formed within one ore substage, corresponds to the type of gold-galena-chalcopyrite with barite. The established similarity of native gold in the Southern Ak-Dag occurrence and other deposits in the Aldan-Maadyr ore cluster in terms of P-T parameters of ore formation and mineralogical and geochemical features, as well as association of the ore mineralization with beresites, indicate the possibility of discovering industrial ore deposits in the region and confirm its paragenetic relation with Devonian magmatic activity.

CHARACTERIZATION OF PALEOPROTEROZOIC STRUCTURES, AURIFEROUS QUARTZ VEINS, AND HOST ROCKS, FISHER PROPERTY, SEABEE GOLD OPERATION, SASKATCHEWAN, CANADA

2019 ◽  
Author(s):  
Courtney Carol Onstad ◽  
◽  
Kevin M. Ansdell ◽  
Camille A. Partin ◽  
Anders Carlson
Keyword(s):  
Quartz Veins ◽  
Host Rocks

Predictive geochemistry of ore gold in Eastern Transbaikalia

2020 ◽  
Vol 26 (10) ◽  
pp. 6-14
Author(s):  
Yu. Pavlenko ◽  
Keyword(s):  
Gold Mineralization ◽  
Geological Mapping ◽  
Earth’S Crust ◽  
Natural Environments ◽  
Gold Concentration ◽  
Gold Ore ◽  
Natural Concentration ◽  
Eastern Transbaikalia ◽  
Earth's Crust ◽  
Gold Bearing

The subject of the research is the methods of forecasting the Eastern Transbaikalia - a large mining region of Russia, in which the main internal and external criteria for ore content are established by modern geological mapping at a scale of 1:1,000,000. The article considers endogenous geochemical criteria for gold concentration in the Earth’s crust of the region, which constitute a mandatory methodological method for predicting gold ore objects at any scale. The aim of the work is to clarify the achieved level of knowledge about the mineralogical and geochemical criteria for gold concentration in the course of the evolution of the Earth’s crust up to the formation of industrial deposits and the isolation of ore formations. The methodology of the study is to systematize a huge amount of factual material concerning the processes of natural concentration of gold, to analyze its representativeness, to assess the completeness and reliability of published and stock information used to clarify the mineralogical and geochemical criteria for predicting ore gold. Using the chemical properties of gold, the forms of finding gold, amount of it in the forming geological complexes and natural environments, their evolution, distribution in structural and tectonic zones, some causes of concentration and mineralogical and geochemical prediction criteria are considered. Special attention is paid to the need to study and account for nanoscale (dispersed) gold. As the main ore-formation units of gold mineralization, standardized ore formations are defined with a division into gold ore proper, complex gold-bearing and gold-bearing and geological and industrial types of deposits. There are 15 geological and industrial types, of which 13 are transbaikal deposits standards and two are attracted from other regions. These types of deposits differ in the number of objects related to them. Due to some similarity in the composition of ore matter, geological and industrial types differ in the most important classification characteristics for the forecast. Areas of distribution of direct and indirect mineralogical and geochemical features grouped into mineralogical and geochemical forecast criteria are promising for endogenous concentration of gold mineralization

Fluid flow and faulting history of the Iano tectonic window (Southern Tuscany, Italy).

2021 ◽  
Author(s):  
Paolo Fulignati ◽  
Martina Zucchi ◽  
Andrea Brogi ◽  
Enrico Capezzuoli ◽  
Domenico Liotta ◽  
...  
Keyword(s):  
Fluid Inclusions ◽  
Hydrothermal Fluids ◽  
Normal Faults ◽  
High Angle ◽  
Quartz Veins ◽  
History Of ◽  
Tectonic Window ◽  
Liquid Vapor

<p>In the Iano area (Southern Tuscany) a small tectonic window of Tuscan metamorphic units is observed. This belongs to the northernmost part of the so-called Mid-Tuscan ridge and, during Pliocene, formed a submarine high, now defining the easternmost shoulder of the Volterra Pliocene basin. The area gives the opportunity to investigate the complete cycle of negative inversion from crustal thickening to crustal thinning, which characterizes Southern Tuscany. Our new data focus on the western margin of the Iano ridge, and in particular on a system of high angle normal faults that represents the youngest structures of the investigated area. These structures, deformed low angle regional detachments locally juxtaposing the uppermost units of contractional nappe stack (the ophiolite-bearing Ligurian units), with the Tuscan metamorphic units, with an almost complete excision of at least 3.5 Km thick Mesozoic to Tertiary Tuscan nappe succession. The high angle normal faults show variable Plio-Quaternary vertical displacements from few meters to about 500 meters, and acted as pathways for the upwelling of hydrothermal fluids, as revealed by Pleistocene travertine deposits, hydrothermal alteration and occurrence of different generations of fluid inclusions in hydrothermal veins associated with these fault systems. Fluid inclusions were studied in quartz veins hosted in the Verrucano metasediments forming the top of the Tuscan metamorphic unit, as well as in some carbonate lithotypes (Cretaceous to Tertiary in age) of the overlying Tuscan Nappe. Two different kinds of fluid inclusions were documented. The Type 1 are multiphase (liquid + vapor + 1 daughter mineral) liquid-rich fluid inclusions whereas the Type 2 are two-phase (liquid + vapor) liquid-rich fluid inclusions. Type 1 fluid inclusions are primary in origin and were found only in quartz veins present in Verrucano metarudites, whereas Type 2 fluid inclusions occur in quartz veins present in both Verrucano phyllites and quartzites and in the carbonate units of the Tuscan Nappe. These are secondary and can be furthermore distinguished in two sub-populations (Type 2a and Type 2b) on the basis of petrographic observation and microthermometric data. Fluid inclusion investigation evidenced an evolution of the hydrothermal fluids from relatively high-T (~265°C) and hypersaline (35 wt.% NaCl<sub>equiv.</sub>) fluids trapped at about 100 MPa, to lower temperature (~195°C) and salinity (~9.5 wt.% NaCl<sub>equiv.</sub>) fluids, having circulated in the high-angle fault system. Based on the new data and a revision of the local tectonic setting a fluid-rock interaction history has been reconstructed with new hints and constraints for the Plio-Quaternary extensional history of the Volterra basin.</p>

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