Fluid chemistry and evolution of hydrothermal fluids in an Archaean transcrustal fault zone network: the case of the Cadillac Tectonic Zone, Abitibi greenstone belt, Canada

2007 ◽  
Vol 44 (6) ◽  
pp. 745-773 ◽  
Author(s):  
P Neumayr ◽  
S G Hagemann ◽  
D A Banks ◽  
B WD Yardley ◽  
J -F Couture ◽  
...  
Keyword(s):  
Hydrothermal Fluid ◽  
Gold Mineralization ◽  
Shear Zones ◽  
Wall Rock ◽  
Higher Order ◽  
Hydrothermal Fluids ◽  
Tectonic Zone ◽  
Quartz Veins ◽  
Hydrothermal Quartz ◽  
Lower Fluid

Detailed fluid geochemistry studies on hydrothermal quartz veins from the Rouyn-Noranda and Val-d'Or areas along the transcrustal Cadillac Tectonic Zone (CTZ) indicate that unmineralized (with respect to gold) sections of the CTZ contained a distinct CO2-dominated, H2S-poor hydrothermal fluid. In contrast, both gold mineralized sections of the CTZ (e.g., at Orenada #2) and associated higher order shear zones have a H2O–CO2 ± CH4–NaCl hydrothermal fluid. Their CO2/H2S ratios indicate H2S-rich compositions. The Br/Cl compositions in fluid inclusions trapped in these veins indicate that hydrothermal fluids have been equilibrated with the crust. Oxygen isotope ratios from hydrothermal quartz veins in the CTZ are consistently 2‰ more enriched than those of associated higher order shear zones, which are interpreted to be a function of greater fluid/rock ratios in the CTZ and lower fluid/rock ratios, and more efficient equilibration of the hydrothermal fluid with the wall rock, in higher order shear zones. An implication from this study is that the lower metal endowment of the transcrustal CTZ, when compared with the higher metal endowment in higher order shear zones (ratio of about 1 : 1000), may be the result of the lack of significant amounts of H2O–H2S rich fluids in most of the CTZ. In contrast, gold mineralization in the higher order shear zones appear to be controlled by the high H2S activity of the aqueous fluids, because gold was likely transported in a bisulfide complex and was deposited during sulfidation reactions in the wall rock and phase separation in the quartz veins.

Structural setting, textures, and timing of hydrothermal vein systems in the Val d'Or camp, Abitibi, Canada: implications for the evolution of transcrustal, second- and third-order fault zones and gold mineralization

2000 ◽  
Vol 37 (1) ◽  
pp. 95-114 ◽  
Author(s):  
P Neumayr ◽  
S G Hagemann ◽  
J -F Couture
Keyword(s):  
Quartz Vein ◽  
Gold Mineralization ◽  
Shear Zones ◽  
Fault Zones ◽  
Third Order ◽  
Tectonic Zone ◽  
Quartz Veins ◽  
Fluid Systems ◽  
Quartz Grains ◽  
Order Structures

In the Val d'Or camp, Archean Abitibi greenstone belt, Canada, numerous gold-mineralized second- and third-order fault zones are spatially associated with the transcrustal Cadillac Tectonic Zone (CTZ). This situation is used to test whether fluid systems in the CTZ have a similar structural timing to those in the gold-hosting structures, and hence the CTZ could represent the main fluid conduit in the camp. The transcrustal CTZ at Orenada No. 2 contains structurally complex vein systems, with mineralized quartz-tourmaline veins related to both D2 oblique-reverse faulting and F3 dextral asymmetric folding, both of which have been overprinted by unmineralized subhorizontal and subvertical quartz veins. Quartz ± tourmaline veins within second- and third-order shear zones at Paramaque and Rivière Héva also formed during D2 deformation and have been, at least at Rivière Héva, deformed by F3 asymmetric folding. In contrast, mineralized quartz vein systems at Cartier Malartic are controlled by F3 folding and overprinted by late-stage D3 faults which host late quartz-tourmaline veins. Quartz vein textures are consistent with these timing relations, because D2-controlled veins contain deformed quartz grains, whereas quartz in D3-controlled veins is unstrained. The D2 and D3 timing of mineralized quartz veins in the transcrustal CTZ and in second- and third-order structures is consistent with the notion that the CTZ represents the main fluid conduit and that mineralization occurred in linked second- and third-order structures. The different timing of quartz-tourmaline veins in different shear zones indicates that the veins were probably hydraulically linked to the CTZ during at least two different episodes. The location of Cartier Malartic structurally below the CTZ indicates that fluids travelled either downward from the main conduit or that the shear zone was part of the CTZ.

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 (<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.

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.

Regional setting of vein-style gold mineralization around the Goldlund mine, Sandybeach Lake area, northwestern Ontario

1990 ◽  
Vol 27 (12) ◽  
pp. 1590-1608 ◽  
Author(s):  
Lesley Chorlton
Keyword(s):  
Gold Mineralization ◽  
Shear Zones ◽  
Main Body ◽  
Lake Area ◽  
Lateral Shear ◽  
Quartz Veins ◽  
Northwestern Ontario ◽  
Stage 4 ◽  
Shear Sense ◽  
Stage 1

The Sandybeach Lake area was deformed in four stages. Stage 1 produced gently south-southeast-dipping foliations at low angles to bedding. Stage 2 involved draping of these planes and formation of contact-strain aureoles related to the emplacement of granitoid stocks. Stage 3 produced doubly plunging folds, steep foliations, and shear zones, which resulted from regional transpression, with a sinistral lateral shear sense along this arm of the Wabigoon greenstone belt. Stage 4 produced minor folds and shear displacements in some places and final tightening of stage 3 folds in others, compatible with final regional convergence.Regional quartz veins, including those carrying gold, appear to have filled tensional fractures related to bulk belt-perpendicular shortening and belt-parallel extension, sinistral shear, and tightening of folds in sheetlike competent bodies. Veins and mineralization thus coincided with late stage 3 deformation, possibly overlapping stage 4.Auriferous vein occurrences at the Goldlund mine display geometries similar to those of veins in the surrounding region. The main body of auriferous vein mineralization is hosted by a thick, composite metatonalite–metadiorite sheet. The vein system of this zone likely originated during the steepening and axial-plane transposition of the southeast-dipping limb near the southwest-plunging end of a stage 3 fold.

scholarly journals Carbonic fluids in the Hamadi gold deposit, Sudan: origin and contribution to gold mineralization

2017 ◽  
Vol 54 (5) ◽  
pp. 494-511 ◽  
Author(s):  
Xi-hui Cheng ◽  
Jiu-hua Xu ◽  
Jian-xiong Wang ◽  
Qing-po Xue ◽  
Hui Zhang
Keyword(s):  
Gold Deposit ◽  
Melting Temperature ◽  
Fluid Inclusions ◽  
Gold Mineralization ◽  
Narrow Range ◽  
Shear Zones ◽  
Quartz Veins ◽  
Wide Range ◽  
Homogenization Temperatures ◽  
Gold Bearing

The Hamadi gold deposit is located in North Sudan, and occurs in the Neoproterozoic metamorphic strata of the Arabian–Nubian Shield. Two types of gold mineralization can be discerned: gold-bearing quartz veins and altered rock ores near ductile shear zones. The gold-bearing quartz veins are composed of white to gray quartz associated with small amounts of pyrite and other polymetallic sulfide minerals. Wall-rock alterations include mainly beresitization, epidotization, chloritization, and carbonatization. CO2-rich inclusions are commonly seen in gold-bearing quartz veins and quartz veinlets from gold-bearing altered rocks; these include mainly one-phase carbonic (CO2 ± CH4 ± N2) inclusions and CO2–H2O inclusions with CO2/H2O volumetric ratios of 30% to ∼80%. Laser Raman analysis does not show the H2O peak in carbonic inclusions. In quartz veins, the melting temperature of solid CO2 (Tm,CO2) of carbonic inclusions has a narrow range of −59.6 to −56.8 °C. Carbonic inclusions also have CO2 partial homogenization temperatures (Th,CO2) of −28.3 to +23.7 °C, with most of the values clustering between +4.0 and +20 °C; all of these inclusions are homogenized into the liquid CO2 state. The densities range from 0.73 to 1.03 g/cm3. XCH4 of carbonic fluid inclusions ranges from 0.004 to 0.14, with most XCH4 around 0.05. In CO2–H2O fluid inclusions, Tm,CO2 values are recorded mostly at around −57.5 °C. The melting temperature of clathrate is 3.8–8.9 °C. It is suggested that the lowest trapping pressures of CO2 fluids would be 100 to ∼400 MPa, on the basis of the Th,CO2 of CO2-bearing one-phase (LCO2) inclusions and the total homogenization temperatures (Th,tot) of paragenetic CO2-bearing two-phase (LCO2–LH2O) inclusions. For altered rocks, the Tm,CO2 of the carbonic inclusions has a narrow range of −58.4 to ∼−57.0 °C, whereas the Th,CO2 varies widely (−19 to ∼+29 °C). Most carbonic inclusions and the carbonic phases in the CO2–H2O inclusions are homogenized to liquid CO2 phases, which correspond to densities of 0.70 to ∼1.00 g/cm3. Fluid inclusions in a single fluid inclusion assemblage (FIA) have narrow Tm,CO2 and Th,CO2 values, but they vary widely in different FIAs and non-FIAs, which indicates that there was a wide range of trapping pressure and temperature (P–T) conditions during the ore-forming process in late retrograde metamorphism after the metamorphism peak period. The carbonic inclusions in the Hamadi gold deposit are interpreted to have resulted from unmixing of an originally homogeneous aqueous–carbonic mixture during retrogress metamorphism caused by decreasing P–T conditions. CO2 contributed to gold mineralization by buffering the pH range and increasing the gold concentration in the fluids.

scholarly journals The geological and structural controls of gold mineralization in Qala en Nahal-Um Sagata region, South Gedarif, Sudan

2020 ◽  
Vol 59 (3) ◽  
pp. 19-26
Author(s):  
Musab Awad Ahmed HASSAN ◽  
◽  
Aleksandr Evgen’yevich KOTEL’NIKOV ◽  
Keyword(s):  
Gold Mineralization ◽  
Mineral Exploration ◽  
Structural Evolution ◽  
Absorption Spectrometry ◽  
Shear Zones ◽  
Structural Features ◽  
Geological Structure ◽  
Geological Mapping ◽  
Quartz Veins ◽  
Ophiolitic Complex

Relevance and purpose of the work. The study area is located in Gedarif state in Sudan. The ongoing work is aimed at solving fundamental problems of the geological structure of the Qala En Nahal-Um Saqata Ophiolitic Complex and applied tasks of mineral exploration. Detailed studies are being conducted for the first time in this area. The purpose of the investigation is to study the geological and structural features of the region, as well as to obtain information about the localization of gold mineralization. Methods of research. Within the study area, a geological mapping of the ophiolitic complex was carried out. It’s included an analysis of structural elements for investigation of the structural evolution and the phases of deformation. Chemical analysis of the mineralized quartz veins to determine the gold was carried out by Atomic Absorption Spectrometry (AAS) technique at the ALS Laboratory in Saudi Arabia. Results of the work. The investigation of the structural evolution revealed at least three phases of deformation. The gold mineralization occurs in auriferous quartz veins, which are hosted in metavocano-sedimentary, sheared synorogenic granites and listvenites. The auriferous quartz veins are structurally controlled by dominantly NE main shear directions. Conclusions. The gold mineralization in the area can be classified shear zone related mineralization, which is formed during the final event accomplished by crustal cooling, and formation of auriferous quartz vein along shear zones. Gold concentration were recorded in both quartz veins and associates alteration rocks. The area is promising for the presence of a gold deposit.

Relationship of hydrothermal alteration to structure and stratigraphy at the Coniaurum gold mine, northern Ontario

1988 ◽  
Vol 25 (12) ◽  
pp. 2028-2040
Author(s):  
Darwin W. Piroshco ◽  
C. Jay Hodgson
Keyword(s):  
Hydrothermal Alteration ◽  
Volcanic Rocks ◽  
Shear Zones ◽  
Wall Rock ◽  
Gold Mine ◽  
Northern Ontario ◽  
Quartz Veins ◽  
Mineral Assemblages ◽  
Relationship Of ◽  
Ore Zones

The gold mineralized zones of the Coniaurum mine, Porcupine camp, northeastern Ontario, are on the eastern end of the northeast-trending Hollinger–Mclntyre ore system. The ore zones are quartz–ankerite (plus accessories) veins and vein systems and associated pyritic wall rock, hosted by a sequence of mafic volcanic rocks and discordant quartz–feldspar porphyry stocks of Archean age.A least altered facies and three alteration facies can be distinguished within the mafic volcanic rocks: a chlorite facies, an ankerite facies, and a vein envelope facies. The chlorite facies is widespread, overprints the least altered facies (i.e., chlorite replaces actinolite), and hosts barren and locally mineralized quartz veins bordered by vein envelope facies alteration. The ankerite facies is coextensive with subparallel shear zones, which crosscut me axial trace of the Coniaurum anticline, and hosts most of the mineralized vein systems. Addition mineralization occurs within graphitic sediments in the crest area of the Coniaurum anticline.On the basis of the above relationships, the shear zones, hydrothermal alteration, and mineralization are interpreted to be late (i.e., syn- to post-development of the Coniaurum anticline).The mineral assemblages of the chlorite and ankerite alteration facies are interpreted as resulting from lateral gradients in [Formula: see text]. Replacement textures between minerals at the alteration facies boundaries indicate the hydrothermal system first grew outwards but later collapsed inwards and the vein envelope facies is superimposed on the more widespread ankerite and chlorite facies.

The Saidu Gold Deposit of Southern Altai, China: Mineralizing Stages and Ore-Forming Fluids Evolution

2013 ◽  
Vol 734-737 ◽  
pp. 215-218
Author(s):  
Guo Rui Zhang ◽  
Jiu Hua Xu ◽  
Li Hua Shan ◽  
Hui Zhang ◽  
Xiao Feng Wei
Keyword(s):  
Gold Deposit ◽  
Gold Mineralization ◽  
Early Stage ◽  
Shear Zones ◽  
Ductile Shear Zone ◽  
Tectonic Zone ◽  
Low Salinity ◽  
Ore Bodies ◽  
Evolution Characteristics ◽  
Homogenization Temperatures

The Saidu gold deposit is located in the northwest part of Ertix Tectonic Zone in Xinjiang. The ore bodies occur in altered mylonite zones within the Mar-kakol giant fault zone and are controlled by the ductile shear zone. The structural-metallogenic fluids of the early stage are characterized by mesothermal-hydrothermal CO2-N2-rich fluids, with homogenization temperatures of fluid inclusions being 252~408°C. The tectonic-metallogenic fluids at the middle stage are characterized by CO2-H2O fluids, with homogenization temperatures being 203~326°C. The fluids at the late stage were epithermal-mesothermal low salinity aqueous solutions, with homogenization temperatures being 120~221°C. The main gold mineralization was related to the post-orogenic extension environment, with the evolution characteristics corresponding to the evolution of shear zones.

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.

Sign in / Sign up

Export Citation Format

Share Document