scholarly journals Geological, Geochemical, and Mineralogical Constraints on the Genesis of the Polymetallic Pb-Zn-Rich Nuocang Skarn Deposit, Western Gangdese, Tibet

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 839
Author(s):  
Junsheng Jiang ◽  
Shunbao Gao ◽  
Youye Zheng ◽  
David R. Lentz ◽  
Jian Huang ◽  
...  
Keyword(s):  
Oxygen Fugacity ◽  
Meteoric Water ◽  
Ph Value ◽  
Volcanic Rocks ◽  
Volcanic Area ◽  
Skarn Deposit ◽  
Epithermal Deposits ◽  
Magmatic Fluids ◽  
Magmatic Volatiles ◽  
Geochemical Analyses

The Nuocang Pb-Zn deposit is a newly discovered polymetallic skarn deposit in the southern Lhasa subterrane, western Gangdese, Tibet. The skarn occurs at the contact between the limestone of Angjie Formation and the Linzizong volcanic rocks of Dianzhong Formation (LDF), and the subvolcanic granite porphyry intruding those formations; the contact metasomatic skarn is well zoned mineralogically and texturally, as well as geochemically. The skarn minerals predominantly consist of an anhydrous to hydrous calc-silicate sequence pyroxene–garnet–epidote. The endoskarn mainly consists of an assemblage of pyroxene, garnet, ilvaite, epidote, and quartz, whereas the exoskarn is characterized proximal to distally, by decreasing garnet, and increasing pyroxene, ilvaite, epidote, chlorite, muscovite, quartz, calcite, galena, and sphalerite. Geochemical analyses suggest that the limestone provided the Ca for all the skarn minerals and the magmatic volatiles were the main source for Si (except the skarnified hornfels/sandstone, and muscovite-epidote-garnet-pyroxene skarn possibly from the host sandstones), with Fe and Mn and other mineralizing components. During the hydrothermal alteration, the garnet-pyroxene skarn and pyroxene-rich skarn gained Si, Fe, Mn, Pb, Zn, and Sn, but lost Ca, Mg, K, P, Rb, Sr, and Ba. However, the skarnified hornfels/sandstone, and muscovite-epidote-garnet-pyroxene skarn gained Fe, Ca, Mn, Sr, Zr, Hf, Th, and Cu, but lost Si, Mg, K, Na, P, Rb, Ba, and Li. The REEs in the skarn were sourced from magmatic fluids during the prograde stage. Skarn mineral assemblages and geochemistry indicate the skarn in the Nuocang deposit were formed in a disequilibrated geochemical system by infiltrative metasomatism of magmatic fluids. During the prograde stage, garnet I (And97.6Gro1.6) firstly formed, and then a part of them incrementally turned into garnet II (And64.4Gro33.8) and III (And70.22Gro29.1). The subsequent substitution of Fe for Al in the garnet II and III indicates the oxygen fugacity of the fluid became more reduced, then resulted in formation of significant pyroxene. However, the anisotropic garnet IV (And38.5Gro59.8) usually replaced the pyroxene. In the retrograde stage, the temperature decreased and oxygen fugacity increased, but hydrolysis increased with epidote, ilvaite, chlorite I, and muscovite forming with magnetite. The continuing decreasing temperature and mixing with meteoric water lead to Cu, Pb, and Zn saturation as sulfides. After the sulfides deposition, the continued mixing with large amounts of cold meteoric water would decrease its temperature, and increase its pH value (neutralizing), promoting the deposition of significant amounts of calcite and chlorite II. The geological, mineralogical, and geochemical characteristics of Nuocang skarn, suggest that the Nuocang deposit is of a Pb-Zn polymetallic type. Compared to the other typical skarn-epithermal deposits in the Linzizong volcanic area, it indicates that the Nuocang deposit may have the exploration potential for both skarn and epithermal styles of mineralization.

scholarly journals Geology and characteristics of Pb-Zn-Cu-Ag skarn deposit at Ruwai, Lamandau Regency, Central Kalimantan

2015 ◽  
Vol 3 (1) ◽  
Author(s):  
Arifudin Idrus ◽  
Lucas Donny Setijadji ◽  
Fenny Tamba ◽  
Ferian Anggara
Keyword(s):  
Low Temperature ◽  
Hydrothermal Fluid ◽  
Meteoric Water ◽  
Volcanic Rocks ◽  
Thrust Fault ◽  
Strike Slip ◽  
Skarn Deposit ◽  
Central Kalimantan ◽  
Low Salinity ◽  
Ore Mineralization

This study is dealing with geology and characteristics of mineralogy, geochemistry and physicochemical conditions of hydrothermal fluid responsible for the formation of skarn Pb-Zn-Cu-Ag deposit at Ruwai, Lamandau Regency, Central Kalimantan. The formation of Ruwai skarn is genetically associated with calcareous rocks consisting of limestone and siltstone (derived from marl?) and controlled by NNE-SSW-trending strike slip faults and localized along N 70° E-trending thrust fault, which also acts as contact zone between sedimentary and volcanic rocks in the area. Ruwai skarn is mineralogically characterized by prograde alteration (garnet and clino-pyroxene) and retrograde alteration (epidote, chlorite, calcite and sericite). Ore mineralization is characterized by sphalerite, galena, chalcopyrite and Ag-sulphides (particularly acanthite and argentite), which formed at early retrograde stage. Geochemically, SiO2 is enriched and CaO is depleted in limestone, consistent with silicic alteration (quartz and calc-silicate) and decarbonatization of the wallrock. The measured reserves of the deposit are 2,297,185 tonnes at average grades of 14.98 % Zn, 6.44 % Pb, 2.49 % Cu and 370.87 g/t Ag. Ruwai skarn orebody originated at moderate temperature of 250-266 °C and low salinity of 0.3-0.5 wt.% NaCl eq. The late retrograde stage formed at low temperature of 190-220 °C and low salinity of ~0.35 wt.% NaCl eq., which was influenced by meteoric water incursion at the late stage of the Ruwai Pb-Zn-Cu-Ag skarn formation. Keywords: Geology, skarn, mineralogy, geochemistry, Ruwai, Central Kalimantan

scholarly journals GEOHYDROTHERMAL MODEL OF ARJUNO, WELIRANG AND PENANGGUNGAN VOLCANOES EAST JAVA, INDONESIA

2018 ◽  
Vol 2 (1) ◽  
pp. 37
Author(s):  
Untung Sumotarto ◽  
F. Hendrasto ◽  
Wibagiyo Wibagiyo
Keyword(s):  
Geothermal Energy ◽  
Meteoric Water ◽  
Volcanic Rocks ◽  
Isotopic Analysis ◽  
Igneous Rocks ◽  
Volcanic Area ◽  
Maturity Level ◽  
Energy Potential ◽  
Potential Resource ◽  
Water Springs

Indonesia is a country having a high geothermal energy potential. The geothermal energy in Java island, as a volcanic row island, has been explored and produced. One of the area that has not been produced is volcanic area around Arjuno, Welirang and Penanggungan (AWP) located in East Java. Geochemical survey has been performed to explore a more detailed objective in exploring the potential resource of geothermal energy of this area. Chemical and isotopic analysis shows the maturity level of waters taken from water springs in the area. The immature water from the water springs is interpreted coming mostly from meteoric water which flows quite fast forming water springs around the area. Geohydrothermally, the water flows through porous and permeable volcanic rocks that receive heat from igneous rocks existing together in the area. The igneous rocks are flowing heat conductively from magma below the AWP volcanoes.

scholarly journals Structural and Chemical Controllers of the North and Northwest of Torud Based on Involved Fluid Studies, Structural and Geochemical Analyses

2021 ◽  
Vol 15 (3) ◽  
pp. 339-349
Author(s):  
Fatemeh Baseri ◽  
Arash Gourabjeri Pour ◽  
Nima Nezafati
Keyword(s):  
Volcanic Rocks ◽  
Mining Area ◽  
Hydrothermal Solutions ◽  
Base Metals ◽  
Laboratory Studies ◽  
Scattered Space ◽  
The North ◽  
Geochemical Analyses ◽  
Geochemical Studies ◽  
Semnan Province

Chah Mura mining area in Semnan province is located 30 km southwest of Shahroud and 20 km north of Torud village with an area of 35 km2 and includes a part of 1:250,000 Torud plate. Structurally, this area is located in the northeastern part of Central Iran and in the center of the volcanic-intrusive arc of Torud-Chah Shirin. Rock units of the area are volcanic and pyroclastic, depending on the Eocene age. Exposed assemblages in the Chah Mura area, based on field and laboratory studies, can be divided into basalt, andesite, andesite-basalt, trachyandesite, trachyandesibasalt and small outcrops of pyroclastic units in the form of agglomerates and sediments of sandstone and conglomerate. Volcanic rocks are influenced by sub-volcanic masses younger than Eocene with an intermediate to basic composition, and their predominant textures are granular, porphyroid with microcrystalline to microintragranular background. Finally, the units are cut by dikes. In this area, mineralization is mainly in the control of sub-faults and subvolcanic massifs. Mineralization is in the form of vein-veinlet, filling empty and scattered space in the oxidation-supergen stage. Mineral sequences include pyrite, chalcopyrite, chalcocite, digenite and covellite, cuprite, tenorite, natural copper, malachite, azurite, and iron oxides and hydroxides. Geochemical studies indicate that copper does not correlate well with any of the base metals and depositing elements. Copper shows only a relative correlation with silver. Micrometric studies of fluid inclusions in samples from this area indicate dilution as a result of mixing hydrothermal solutions with atmospheric fluids in formation of this reserve.

scholarly journals A revised map of volcanic units in the Oman ophiolite: insights into the architecture of an oceanic proto-arc volcanic sequence

2019 ◽  
Author(s):  
Thomas M. Belgrano ◽  
Larryn W. Diamond ◽  
Yves Vogt ◽  
Andrea R. Biedermann ◽  
Samuel A. Gilgen ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Sedimentary Cover ◽  
Phase 1 ◽  
Volcanic Rocks ◽  
Shear Zones ◽  
Magma Ascent ◽  
Upper Crust ◽  
Vms Deposits ◽  
Geochemical Analyses ◽  
Semail Ophiolite

Abstract. Recent studies have revealed genetic similarities between Tethyan ophiolites and oceanic proto-arc sequences formed above nascent subduction zones. The Semail ophiolite (Oman–U.A.E.) in particular can be viewed as an analogue for this proto-arc crust. Though proto-arc magmatism and the mechanisms of subduction-initiation are of great interest, insight is difficult to gain from drilling and limited surface outcrops in submarine fore-arcs. In contrast, the Semail ophiolite, in which the 3–5 km thick upper-crustal succession is exposed in an oblique cross-section, presents an opportunity to assess the architecture and volumes of different volcanic rocks that form during the protoarc stage. To determine the distribution of the volcanic rocks and to aid exploration for the volcanogenic massive sulphide (VMS) deposits that they host, we have re-mapped the volcanic units of the Semail ophiolite by integrating new field observations, geochemical analyses and geophysical interpretations with pre-existing geological maps. By linking the major element compositions of the volcanic units to rock magnetic properties, we were able to use aeromagnetic data to infer the extension of each outcropping unit below sedimentary cover, resulting in in a new map showing 2100 km2 of upper-crustal bedrock. Whereas earlier maps distinguished two main volcanostratigraphic units, we have distinguished four, recording the progression from early spreading-axis basalts (Geotimes) through to axial to off-axial depleted basalts (Lasail), to post-axial tholeiites (Tholeiitic Alley) and finally boninites (Boninitic Alley). Geotimes (Phase 1) axial dykes and lavas make up ~55 vol% of the Semail upper crust, whereas post-axial (Phase 2) lavas constitute the remaining ~ 45 vol % and ubiquitously cover the underlying axial crust. The Semail boninites occur as discontinuous accumulations up to 2 km thick at the top of the sequence and constitute ~ 15 vol % of the upper crust. The new map provides a basis for targeted exploration of the gold-bearing VMS deposits hosted by these boninites. The thickest boninite accumulations occur in the Fizh block, where magma ascent occurred along crustal-scale faults that are connected to shear zones in the underlying mantle rocks, which in turn are associated with economic chromitite deposits. Locating major boninite feeder zones may thus be an indirect means to explore for chromitites in the underlying mantle.

scholarly journals Iron Isotopes Constrain the Metal Sources of Skarn Deposits: A Case Study from the Han-Xing Fe Deposit, China

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 951
Author(s):  
Bin Zhu ◽  
Hongfu Zhang ◽  
M. Santosh ◽  
Benxun Su ◽  
Pengfei Zhang ◽  
...  
Keyword(s):  
Major Elements ◽  
Ore Deposits ◽  
Magmatic Fluid ◽  
Skarn Deposit ◽  
Mass Balance Calculation ◽  
Positive Correlation ◽  
Fe Isotopes ◽  
Magmatic Fluids ◽  
Skarn Deposits

Magmatic fluids and leaching of rocks are regarded as the two sources of magmatic hydrothermal deposits, but their relative contributions to the metals in the deposits are still unclear. In this study, we combine major elements and Fe isotopes in two sets of rocks from the Han-Xing iron skarn deposit in China to constrain the iron sources. The positive correlation between the δ56Fe and ∑Fe2O3/TiO2 of altered diorites (∑Fe2O3 refers to the total iron) demonstrates that heavy Fe isotopes are preferentially leached from diorites during hydrothermal alteration. However, except for the pyrite, all the rocks and minerals formed in the skarn deposit are enriched in the light Fe isotope relative to the fresh/less altered diorites. Therefore, besides the leaching of rocks, the Fe isotopically light magmatic fluid also provides a large quantity of iron for this deposit. Based on the mass balance calculation, we conclude that iron from magmatic fluid is almost 2.6 times as large as that from the leaching of rocks. This is the first study to estimate the relative proportions of iron sources for Fe deposits by using Fe isotopes. Here, we propose that the high δ56Fe of magmatic intrusions combining the positive correlation between their ∑Fe2O3/TiO2 and δ56Fe could be taken as a fingerprint of exsolution or interaction with magmatic fluids, which contributes to the exploration of magmatic hydrothermal ore deposits.

scholarly journals Genesis of Volcanic Rocks in the Zijinshan Ore District, SE China: Implications for Porphyry-Epithermal Mineralization

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 200 ◽  
Author(s):  
Zheng-Zheng Feng ◽  
Zhong-Jie Bai ◽  
Hong Zhong ◽  
Wei-Guang Zhu ◽  
Shi-Ji Zheng
Keyword(s):  
Oxygen Fugacity ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Parental Magma ◽  
High Oxygen ◽  
Magma Source ◽  
High Water Content ◽  
High Oxygen Fugacity ◽  
Epithermal Mineralization ◽  
T Values

Volcanic rocks, as the extrusive counterparts of the mineralized intrusions, can provide important information on the magma source, petrogenesis, and metallogenic conditions of the coeval porphyry-epithermal system. Shanghang Basin volcanic rocks are spatially and temporally related to a series of adjacent porphyry-epithermal Cu–Au deposits, and they can be used as a window to study the related deposits. Two laser-ablation–inductively coupled plasma–mass spectrometry zircon U–Pb analyses of the volcanic rocks yield weighted mean ages of ~105 Ma, identical to the age of the coeval porphyry-epithermal mineralization. Rocks have SiO2 contents of 55.4 to 74.8 wt % and belong to the high-K to shoshonitic series, characterized by strong differentiation of light rare-earth elements (REEs) relative to heavy REEs (mean LaN/YbN = 16.88); enrichment in light REEs, Rb, Th, and U; and depletion in Nb, Ta, Zr, Hf, and Ti. The volcanic rocks display (87Sr/86Sr)i values of 0.709341 to 0.711610, εNd(t) values of −6.9 to −3.3 εHf(t) values of −3.95 to −0.30, and δ18O values of 6.07‰–6.79‰, suggesting that the parental magmas were derived from a mantle source enriched by subduction-related progress. SiO2 content shows a strong negative correlation with the contents of some major and trace elements, indicating that fractional crystallization played an important role in the generation of these rocks. A binary mixing model of Hf–O isotopes gives an estimated degree of crustal contamination of 30%. In addition, magnetite crystallized early, and the samples showed high zircon EuN/EuN* values (0.48–0.68), indicating that the parental magma had a high oxygen fugacity. The inferred suppression of plagioclase crystallization and increasing hornblende crystallization during magma evolution suggest that the magma was water rich. The high-water content and high oxygen fugacity of the magma promoted the dissolving of sulfides containing Cu and Au in the source area and contributed to the migration of ore-forming elements.

scholarly journals Petrogenesis and depositional environment of paleozoic Sedili and Pengerang Volcaniclastics in East Johor Basin, Peninsular Malaysia

2019 ◽  
Vol 76 ◽  
pp. 04009
Author(s):  
Sugeng Sapto Surjono ◽  
Mohd. Shafeea Leman ◽  
Che Aziz Ali ◽  
Kamal Roslan Mohamed ◽  
Fathan Hanifi Mada M
Keyword(s):  
Depositional Environment ◽  
Active Continental Margin ◽  
Volcanic Rocks ◽  
Peninsular Malaysia ◽  
Calc Alkaline ◽  
Great Abundance ◽  
Volcaniclastic Rocks ◽  
Geochemical Analyses ◽  
Depositional Setting ◽  
Magma Series

Volcaniclastic rocks in East Johor Basin are found in a relatively great abundance comprising Sedili and Pengerang Formations excluding the metamorphics, siliciclastics, and granites. Since the volcaniclastic rocks are found in a different formation, this study aims to find out the characteristics of each rock. Geology, petrography, and geochemical analyses were elaborated to reveal the petrogenesis and depositional environment in the studied area on the basis of fieldwork data and 24 samples collected from outcrops. The Sedili and Pengerang Formations are dominated by acidic rocks of rhyolite, rhyodacite, ignimbrite, and lava classifiied into calc-alkaline magma series which indicates a subduction-related product. Moreover, those acidic rocks are grouped into active continental margin. Eventhough volcanic rocks in Sedili and Pengerang Formations exhibit similar characteristics, they are different in several major contents. Therefore, it is inferred that both Sedili and Pengerang Formations were deposited in different phase. Coincidentally, depositional environment of both formations is also distinct. Sedili Formation were deposited in the subaerial to shallow marine, meanwhile, Pengerang Formation is interpreted to be deposited in deeper depositional setting.

scholarly journals Mineralogy and genesis of the Ni–Co lateritic regolith deposit of the Çaldağ area (Manisa, western Anatolia), Turkey

2018 ◽  
Vol 55 (3) ◽  
pp. 252-271 ◽  
Author(s):  
Cahit Helvacı ◽  
Tolga Oyman ◽  
İbrahim Gündoğan ◽  
Hasan Sözbilir ◽  
Osman Parlak ◽  
...  
Keyword(s):  
Chemical Weathering ◽  
Middle Eocene ◽  
Volcanic Rocks ◽  
Polarized Light ◽  
Ultramafic Rocks ◽  
Western Anatolia ◽  
Fe Oxides ◽  
Transmission Electron ◽  
Dry Conditions ◽  
Geochemical Analyses

The Çaldağ Ni–Co deposit is characterized by a reddish brown oxide lateritic regolith, containing residual Ni deposit formed by the intense tropical weathering of peridotites. Nickel–Co ore is associated with transported ferricrete during the late Paleocene – middle Eocene, represented by colloform Fe oxides and residual lateritization during the Oligocene. The lateritic regoliths are developed over dunitic ultramafic rocks and consist mainly of smectite, berthierine, kaolinite, gypsum, pyrite, takovite, and pecoraite. These units were examined using polarized-light microscopy, X-ray diffraction, scanning and transmission electron microscopy, and geochemical methods. Mineralogical zonation from the base of the profile upwards has the following zones: ultramafic bedrocks, serpentinized ultramafic rocks (saprock), saprolite, carbonate- and sulfide-bearing zone, ferruginous saprolite zone, and silcrete. In addition, Fe oxides, smectite and opal-CT, and quartz increase towards the surface, whereas olivine, pyroxene, and serpentine decrease upwards in response to chemical weathering. Nickel–Co mineralization associated with Fe oxides and smectitic clays formed under wet and dry conditions, respectively, as a result of an increased Fe2O3 + Al2O3 + Ni + Co/MgO ratio. Field observations and mineralogical and geochemical analyses reveal that the smectite formed under basic conditions was controlled by multistage chemical weathering of ultramafic and volcanic rocks and by the concentrations of Si, Al, Fe, and Mg. Locally, concentrations of S in conjunction with Fe and Ca resulted in precipitation of goethite–hematite, gypsum, and pyrite in dissolution voids in association with smectite under acidic conditions that developed in a well-drained system.

The role of fluids during formation and evolution of the southern Superior Province lithosphere: an overview

2000 ◽  
Vol 37 (2-3) ◽  
pp. 135-164 ◽  
Author(s):  
Robert Kerrich ◽  
John Ludden
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Greenstone Belt ◽  
Meteoric Water ◽  
Gold Deposits ◽  
Lode Gold ◽  
Magmatic Fluids ◽  
Abitibi Subprovince ◽  
Lode Gold Deposits ◽  
Archean Basement

Models for fluid flow and hydrothermal alteration for the Abitibi greenstone belt are reviewed in the light of Lithoprobe results in the region. In the Abitibi greenstone belt, eruption of volcanic sequences over 2750-2700 Ma was accompanied by pervasive low-temperature hydrothermal alteration at high water/rock ratios, giving systematic 18O-enrichment. Archean ambient ocean water bottom temperatures were likely ca. 30°C, and δ18O ~0 ± 1‰. Chert-iron formations precipitated from low temperature hydrothermal discharge. Base metal massive sulphide deposits formed at or near the seafloor from focussed discharge of high-temperature (~300-400°C) fluids in convective cells sited above subvolcanic intrusions. The ore fluids were evolved seawater that had undergone compositional and isotopic evolution by high-temperature, low water/rock exchange with the volcanic pile to NaCl (3-7 wt.%) or CaCl2-NaCl (up to 30 wt.%) brines of δ18O = 0-8‰. These volcanic associated hydrothermal deposits are associated with greenstone belt asemblages in the northern Abitibi subprovince that were emplaced as a series of thrust slices over the Opatica plutonic belt. In the southern Abitibi subprovince the hydrothermal deposits were associated with a series of rift basins (Noranda, Val d'Or, etc.), formed on top of accreted oceanic assemblages comprising primitive arcs and plateaus, or in protoarcs, and associated with oblique convergence. Contemporaneous erosion of emergent arcs and the older cratonic provenance terrane of the Pontiac subprovince by orographic rainfall, and submarine weathering, fed first-cycle vol cano genic sediments to depositional basins in the Abitibi, but siliciclastic sediments of mixed old 3 Ga continent and 2.7 Ga arc provenance in the Pontiac subprovince. Abitibi subprovince turbidites were more weathered and 18O-enriched than Pontiac subprovince equivalents. Subduction-accretion assembly of the Opatica-Abitibi and Pontiac terranes involved allochthonous thrusting of the Abitibi subprovince over the Pontiac subprovince. There were several pulses of granitoid magmatism during accretionary assembly over 2695 to 2674 Ma. Syn- to late-tectonic tonalites were generated by melting of hot young hydrous ocean crust in a shallow-dipping intraoceanic subduction zone. The intrusions exsolved small quantities of magmatic fluids that formed Cu-Zn showings. Late-tectonic shoshonites formed at [Formula: see text]80 km in subarc mantle wedge by slab dehydration-wedge melting. This late-stage of arc development involved transfer of significant quantities of gas-rich alkaline magmas 80+ km through the lithosphere along the accretionary terrane bounding structures, and produced small phosphorus and barite deposits. Synmagmatic metamorphism was of the high-temperature low-pressure type, and occurred in several pulses; water/rock ratios were generally low distal from structures. Tens of thousands of cubic kilometres of fluids generated by dehydration reactions at the base of the subduction-accretion complex, during thermal relaxation following collision and the main granitoid pulses, advected up terrane boundary structures and locally generated lode gold deposits. At the highest structural levels these fluids mixed with Archean meteoric water where δ18O < 0. A second metamorphism (M2) occurred over 2645 to 2611 Ma leading to melting of Pontiac sediments and formation of S-type granites. Deposits of Mo, Th, and P were precipitated from magmatic fluids of δ18O 8-9‰. M2 variably reset radiogenic and stable isotope systems in nonrobust minerals of vol canogenic massive sulphide and lode gold deposits. Hypersaline CaCl2 formation brines evolved in Paleoproterozoic glaciogenic sediments; these penetrated into the Archean basement where they redistributed gold and are pervasively present as low-temperature secondary brine inclusions. The Matachewan (2.5 Ga) and Hearst dyke swarms drove higher temperature advection of the brines, and Ag-Co-Ni sulpharsenide deposits formed by thermal evolution of the brines driven by the Nipissing diabase dyke swarm at ~2219 Ma. Local resetting of 40Ar/39Ar spectra between 2550 and 2200 Ma was the product of tectonic pumping of fluids along reactivated Archean structures, possibly due to coupling of the 200 km thick mantle lithosphere to Archean crust. Seismic evidence for late overprinting of the lower crust and growth of 2450 Ma zircon rims in lower crustal assemblages were associated with this event. There was also fluid activity at 1950 to 1850 Ma due to the Hudsonian orogen induced Kapuskasing event. Hypersaline CaCl2-rich brines formed in the Paleozoic sedimentary cover (~500 Ma), penetrated deep (>5 km) into the Archean basement, and comprise vast reservoirs of hypersaline brines deep in the Shield. The brines precipitated prehnite-laumontite veins that record hundreds of increments of dilation. Subglacial 18O-depleted fluids penetrated to shallow ([Formula: see text]1 km) depths in the Quaternary; they form mixing lines with the hypersaline end member. Extremely D-depleted (-400 to -100‰) CH4 and H discharge in mining districts of the Shield. The depleted H may form by radiolysis of H2O and (or) by a Fischer-Tropsch type process. The hypersaline brine end-member was shifted to the left of the meteoric water line by exchange with D-depleted H.

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