Deformation Mechanisms in Orogenic Gold Systems During Aseismic Periods: Microstructural Evidence from the Central Victorian Gold Deposits, Southeast Australia

2021 ◽  
Vol 116 (8) ◽  
pp. 1849-1864
Author(s):  
Nicholas J.R. Hunter ◽  
Christopher R. Voisey ◽  
Andrew G. Tomkins ◽  
Christopher J.L. Wilson ◽  
Vladimir Luzin ◽  
...  
Keyword(s):  
Gold Deposits ◽  
Orogenic Gold ◽  
Fine Grained ◽  
Quartz Veins ◽  
Seismic Fault ◽  
Columnar Grains ◽  
Deformation Processes ◽  
Aseismic Deformation ◽  
Fault Trace ◽  
Oriented Parallel

Abstract In many orogenic gold deposits, gold is located in quartz veins. Understanding vein development at the microstructural scale may therefore provide insights into processes influencing the distribution of gold, its morphology, and its relationship to faulting. We present evidence that deformation processes during aseismic periods produce characteristic quartz microstructures and crystallographic preferred orientations, which are observed across multiple deposits and orogenic events. Quartz veins comprise a matrix of coarse, subidiomorphic, and columnar grains overprinted by finer-grained quartz seams subparallel to the fault trace, which suggests an initial stage of cataclastic deformation. The fine-grained quartz domains are characterized by well-oriented quartz c-axis clusters and girdles oriented parallel to the maximum extension direction, which reveals that fluid-enhanced pressure solution occurred subsequent to grain refinement. Coarser anhedral gold is associated with primary quartz, whereas fine-grained, “dusty” gold trails are found within the fine-grained quartz seams, revealing a link between aseismic deformation and gold morphology. These distinct quartz and gold morphologies, observed at both micro- and macroscale, suggest that both seismic fault-valving and aseismic deformation processes are both important controls on gold distribution.

scholarly journals Genesis of the Koka Gold Deposit in Northwest Eritrea, NE Africa: Constraints from Fluid Inclusions and C-H-O-S Isotopes

2019 ◽  
Author(s):  
Kai Zhao ◽  
Huazhou Yao ◽  
Jianxiong Wang ◽  
Ghebsha Fitwi Ghebretnsae ◽  
Wenshuai Xiang ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Meteoric Water ◽  
Gold Mineralization ◽  
Early Stage ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Quartz Veins ◽  
Three Phase ◽  
Igneous Origin ◽  
Ne Africa

The Koka gold deposit is located in the Elababu shear zone between the Nakfa terrane and the Adobha Abiy terrane, NW Eritrea. Based on the paragenetic study two main stages of gold mineralization were identified in the Koka gold deposit: 1) an early stage of pyrite-chalcopyrite-sphalerite-galena-gold-quartz vein; and 2) a second stage of pyrite-quartz veins. NaCl-aqueous inclusions, CO2-rich inclusions, and three-phase CO2-H2O inclusions occur in the quartz veins at Koka. The ore-bearing quartz veins formed at 268℃, from NaCl-CO2-H2O(-CH4) fluids averaging 5 wt% NaCl eq. The ore-forming mechanisms include fluid immiscibility during stage I, and mixing with meteoric water during stage II. Oxygen, hydrogen and carbon isotopes suggest that the ore-forming fluids originated as mixtures of metamorphic water, meteoric water and magmatic water, whereas sulfur isotope suggest an igneous origin. Features of geology and ore-forming fluid at Koka deposit are similar to those of orogenic gold deposits, suggesting the Koka deposit might be an orogenic gold deposit related to granite.

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 Genesis of the Koka Gold Deposit in Northwest Eritrea, NE Africa: Constraints from Fluid Inclusions and C–H–O–S Isotopes

Minerals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 201 ◽  
Author(s):  
Kai Zhao ◽  
Huazhou Yao ◽  
Jianxiong Wang ◽  
Ghebsha Fitwi Ghebretnsae ◽  
Wenshuai Xiang ◽  
...  
Keyword(s):  
Gold Deposit ◽  
Gold Mineralization ◽  
Early Stage ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Quartz Veins ◽  
Second Stage ◽  
Three Phase ◽  
Igneous Origin ◽  
Ne Africa

: The Koka gold deposit is located in the Elababu shear zone between the Nakfa terrane and the Adobha Abiy terrane, NW Eritrea. Based on a paragenetic study, two main stages of gold mineralization were identified in the Koka gold deposit: (1) an early stage of pyrite–chalcopyrite–sphalerite–galena–gold–quartz vein; and (2) a second stage of pyrite–quartz veins. NaCl-aqueous inclusions, CO2-rich inclusions, and three-phase CO2–H2O inclusions occur in the quartz veins at Koka. The ore-bearing quartz veins formed at 268 °C from NaCl–CO2–H2O(–CH4) fluids averaging 5 wt% NaCl eq. The ore-forming mechanisms include fluid immiscibility during stage I, and mixing with meteoric water during stage II. Oxygen, hydrogen, and carbon isotopes suggest that the ore-forming fluids originated as mixtures of metamorphic water and magmatic water, whereas the sulfur isotope suggests an igneous origin. The features of geology and ore-forming fluid at the Koka deposit are similar to those of orogenic gold deposits, suggesting that the Koka deposit might be an orogenic gold deposit related to granite.

Structural controls on hypozonal orogenic gold mineralization in the La Ronge Domain, Trans-Hudson Orogen, Saskatchewan

2004 ◽  
Vol 41 (12) ◽  
pp. 1453-1471
Author(s):  
Bruno Lafrance ◽  
Larry M Heaman
Keyword(s):  
Gold Mineralization ◽  
Shear Zones ◽  
Oceanic Lithosphere ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Lake Area ◽  
Structural Controls ◽  
Quartz Veins ◽  
Metavolcanic Rocks ◽  
Orogenic Gold Mineralization

The La Ronge Domain is a granite–greenstone belt in the Saskatchewan segment of the ca. 1.9–1.8 Ga Trans-Hudson Orogen. The La Ronge volcanic arc was accreted to the Archean Hearne craton from ca. 1.87 to 1.86 Ga. Subduction of oceanic lithosphere beneath the accreted La Ronge – Hearne margin produced a voluminous suite of continental-arc intrusions. In the Waddy Lake area, the 1852.6 ± 1.5 Ma Corner Lake stock and 1859 ± 4 Ma and 1861 ± 2 Ma feldspar porphyry dykes crystallized from magmas generated from melting of the subducted oceanic slab. During the ca. 1.83–1.80 Trans-Hudson collision of the Hearne craton with the Archean Sask and Superior cratons, a penetrative regional foliation and a steeply plunging lineation formed within the La Ronge Domain. During further contraction across the domain, the deformation became localized in dextral and oblique-slip shear zones that generally follow contacts between more competent and less competent rock units. Orogenic gold mineralization is associated with quartz veins that are surrounded by hypozonal potassic and sulfidic alteration zones. The Komis gold deposit, the only past-producing gold mine in the Waddy Lake area, formed in the strain shadow of the Round Lake stock during the development of the regional foliation and lineation. Mineralization is associated with quartz veins that cut through tonalite dykes that behaved more brittlely than the surrounding metavolcanic rocks. The Golden Heart and Corner Lake gold deposits are hosted by south-side-up oblique-slip shear zones, which belong to a regional system of structures that extend from Saskatchewan to Manitoba.

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 The Metamorphic Rocks-Hosted Gold Mineralization At Rumbia Mountains Prospect Area In The Southeastern Arm of Sulawesi Island, Indonesia

2017 ◽  
Vol 2 (3) ◽  
pp. 217
Author(s):  
Hasria Hasria ◽  
Arifudin Idrus ◽  
I Wayan Warmada
Keyword(s):  
Gold Deposit ◽  
Gold Mineralization ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Metamorphic Rocks ◽  
Quartz Veins ◽  
Orogenic Gold Deposit ◽  
Ore Mineralization ◽  
Hematite Fe2o3 ◽  
Primary Gold

Recently, in Indonesia gold exploration activities  are not only focused along volcanic-magmatic belts, but also starting to shift along metamorphic and sedimentary terrains. The study area is located in Rumbia mountains, Bombana Regency, Southeast Sulawesi Province. This paper is aimed to describe characteristics of alteration and ore mineralization associated  with metamorphic rock-related gold deposits.  The study area is found the placer and  primary gold hosted by metamorphic rocks. The gold is evidently derived from gold-bearing quartz veins hosted by Pompangeo Metamorphic Complex (PMC). These quartz veins are currently recognized in metamorphic rocks at Rumbia Mountains. The quartz veins are mostly sheared/deformed, brecciated, irregular vein, segmented and  relatively massive and crystalline texture with thickness from 1 cm to 15.7 cm. The wallrock are generally weakly altered. Hydrothermal alteration types include sericitization, argillic, inner propylitic, propylitic, carbonization and carbonatization. There some precious metal identified consist of native gold and ore mineralization including pyrite (FeS2), chalcopyrite (CuFeS2), hematite (Fe2O3), cinnabar (HgS), stibnite (Sb2S3) and goethite (FeHO2). The veins contain erratic gold in various grades from below detection limit <0.0002 ppm to 18.4 ppm. Based on those characteristics, it obviously indicates that the primary gold deposit present in the study area is of orogenic gold deposit type. The orogenic gold deposit is one of the new targets for exploration in Indonesia

scholarly journals Origin and Characteristics of the Shwetagun Deposit, Modi Taung-Nankwe Gold District and the Kunzeik and Zibyaung Deposits, Kyaikhto Gold District in Mergui Belt, Myanmar: Implications for Fluid Source and Orogenic Gold Mineralization

2021 ◽  
Vol 9 ◽  
Author(s):  
Myo Kyaw Hlaing ◽  
Kotaro Yonezu ◽  
Khin Zaw ◽  
Aung Zaw Myint ◽  
May Thwe Aye ◽  
...  
Keyword(s):  
Native Gold ◽  
Gold Mineralization ◽  
Shear Zones ◽  
Wall Rock ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Salinity Range ◽  
Quartz Veins ◽  
Economic Significance ◽  
Gold Bearing

The Mergui Belt of Myanmar is endowed with several important orogenic gold deposits, which have economic significance and exploration potential. The present research is focused on two gold districts, Modi Taung-Nankwe and Kyaikhto in the Mergui Belt comparing their geological setting, ore and alteration mineralogy, fluid inclusion characteristics, and ore-forming processes. Both of the gold districts show similarities in nature and characteristics of gold-bearing quartz veins occurring as sheeted veins, massive veins, stockworks to spider veinlets. These gold deposits are mainly hosted by the mudstone, slaty mudstone, greywacke sandstone, slate, and slaty phyllite of Mergui Group (dominantly of Carboniferous age). The gold-bearing quartz veins generally trend from NNE to N-S, whereas some veins strike NW-SE in all deposits. The gold-bearing quartz veins are mainly occurred within the faults and shear zones throughout the two gold districts. Wall-rock alterations at Shwetagun are mainly silicification, chloritization, and sericitization, whereas in Kyaikhto, silicification, carbonation, as well as chloritization, and sericitization are common. At Shwetagun, the gold occurred as electrum grains in fractures within the veins and sulfides. In Kyaikhto, the quartz-carbonate-sulfide and quartz-sulfide veins appeared to have formed from multiple episodes of gold formation categorizing mainly as free native gold grains in fractures within the veins or invisible native gold and electrum within sulfides. At Shwetagun, the ore minerals in the auriferous quartz veins include pyrite, galena, and sphalerite, with a lesser amount of electrum, chalcopyrite, arsenopyrite, chlorite, and sericite. In Kyaikhto, the common mineralogy associated with gold mineralization is pyrite, chalcopyrite, sphalerite, galena, pyrrhotite, arsenopyrite, marcasite, magnetite, hematite, ankerite, calcite, chlorite, epidote, albite, and sericite. At Shwetagun, the mineralization occurred at a varying temperature from 250 to 335°C, with a salinity range from 0.2 to 4.6 wt% NaCl equivalent. The Kyaikhto gold district was formed from aqueous–carbonic ore fluids of temperatures between 242 and 376°C, low to medium salinity (&lt;11.8 wt% NaCl equivalent), and low CO2 content. The ore-forming processes of the Shwetagun deposit in the Modi Taung-Nankwe gold district and the Kyaikhto gold district are remarkably comparable to those of the mesozonal orogenic gold systems.

Bismuth-bearing assemblages from the Northern Pennine Orefield

1996 ◽  
Vol 60 (399) ◽  
pp. 317-324 ◽  
Author(s):  
R. A. Ixer ◽  
B. Young ◽  
C. J. Stanley
Keyword(s):  
Qualitative Analysis ◽  
Fine Grained ◽  
Quartz Veins ◽  
The North ◽  
Data Form ◽  
Form Part ◽  
Native Bismuth ◽  
Monoclinic Pyrrhotite ◽  
Early Phases ◽  
And Tungsten

AbstractBismuthinite-bearing quartz veins from the Alston Block of the North Pennine Orefield are all close to, or above, the Rookhope and Tynehead cupolas of the buried Weardale Granite. They are uniform in composition and paragenesis and are earlier than the main fluorite-baryte-galena-sphalerite mineralization of the orefield. Rhythmical crystallization of quartz, chalcopyrite and minor pyrite is followed by fluorite-quartz-chalcopyrite-minor sphalerite-altered pyrrhotite mineralization. Early tin-bearing (up to 0.29 wt.% Sn) chalcopyrite encloses trace amounts of bismuthinite (Bi2S3), synchysite (CaREE(CO3)F2), argentopentlandite (Ag(FeNi)8S8) (close to being stoichiometric), pyrrhotite, cubanite and cosalite (Pb2Bi2S5), while early pyrite carries monoclinic pyrrhotite (close to Fe7S8) and tungsten-bearing cassiterite (up to 1.03 wt.% WO3). Bismuthinite is macroscopically visible and is associated with native bismuth and small, fine-grained, spherical aggregates that qualitative analysis suggests may be cosalite crystals. Synchysite and more rarely monazite, xenotime and adularia are intergrown with bismuthinite. These mineralogical data form part of the basis for an increasing awareness of the contribution of the Weardale Granite to the early phases of mineralization in the Alston Block.

Early Growth in the Chemical Vapor Deposition of Tin and TiC and Monitoring by Laser Scattering

1989 ◽  
Vol 168 ◽  
Author(s):  
Max Klein ◽  
Bernard Gallois
Keyword(s):  
Pyrolytic Graphite ◽  
Chemical Vapor ◽  
Early Growth ◽  
Columnar Growth ◽  
Laser Scattering ◽  
Fine Grained ◽  
Steady Rate ◽  
Columnar Grains ◽  
State Growth

AbstractThe early growth of chemically vapor deposited TiN and TiC coatings on pyrolytic graphite was studied in the kinetic- and mass transport-controlled regimes. While steady-state growth of these coatings results in columnar grains, such morphologies do not originate at the substrate/coating interface. Rather, TiC deposition begins on the substrate as fine grains less than 100 nm in diameter. Early TiN growth occurs in layers of 50 nm grains. In both cases, early fine-grained growth occurs at a lower rate than the linear, steady rate observed for columnar growth. A laser scattering technique has been developed as a tool for characterizing early growth through surface roughness. This noncontact method can be used as an in-situ diagnostic to detect changes in the surface of the growing deposit.

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