Geology and geochemistry of the Clear Creek intrusion-related gold occurrences, Tintina Gold Province, Yukon, Canada

2003 ◽  
Vol 40 (5) ◽  
pp. 681-699 ◽  
Author(s):  
Erin E Marsh ◽  
Richard J Goldfarb ◽  
Craig J.R Hart ◽  
Craig A Johnson
Keyword(s):  
Fluid Inclusion ◽  
High Salinity ◽  
Gold Deposition ◽  
Second Phase ◽  
Quartz Veins ◽  
Granitoid Emplacement ◽  
Gold Grade ◽  
Homogenization Temperatures ◽  
Lower Temperature ◽  
Ar Geochronology

The Clear Creek gold occurrences lie within deformed lower greenschist-facies rocks of the western Selwyn basin. They consist of auriferous, sheeted quartz veins that cut six Cretaceous stocks and their hornfels. The veins contain 1–2% combined pyrite and arsenopyrite, with lesser pyrrhotite, bismuthinite, and scheelite, as well as 2–5 g/t Au. New 40Ar/39Ar geochronology of hydrothermal micas indicates that the veins formed within 1–2 million years of granitoid emplacement. Fluid inclusion microthermometry defines a parent ore fluid of ~81 mol.% H2O, 14 mol.% CO2, 4 mol.% NaCl ± KCl, and 1 mol.% CH4, which unmixed into a low- and high-salinity immiscible pair. This suggests a more saline parent fluid and a greater degree of fluid unmixing relative to the other occurrences in the eastern Tintina Gold Province. Inclusions trapped in As- and Bi-rich, high-gold grade veins have homogenization temperatures of 300–350°C, whereas inclusions found in more Ag- and Pb-rich veins are characterized by temperatures of 250–300°C. Fluid inclusion geobarometry suggests hydro-fracturing and gold deposition at 5–7 km depth. The δ18O values of quartz samples range from 13–16‰ (per mil) and δ34S for sulfides are also consistent between –3.0‰ and 0‰, with the exception of some outliers from the Contact Zone of the Pukelman stock that indicate a lower temperature second phase of mineralization. It remains uncertain as to whether the Clear Creek ore fluids were exsolved from magmas at depth or from devolatilization reactions within the contact metamorphic aureoles of the intrusions.

Ore-forming mechanism and its relationship with deformational and metamorphic episodes at Haimur gold mine, Nubian Shield, Egypt

2020 ◽  
pp. 1-19
Author(s):  
Mohamed Abd El Monsef ◽  
Amr Abdelnasser
Keyword(s):  
Eastern Desert ◽  
Gold Deposits ◽  
Fault System ◽  
Gold Deposition ◽  
Second Phase ◽  
Type I ◽  
Nile Valley ◽  
Forming Mechanism ◽  
Ophiolitic Mélange ◽  
Lower Temperature

Abstract The Haimur area represents the central part of the Wadi Allaqi region in the southern block of the Egyptian Eastern Desert near Nasser Lake and the Nile valley. It is made up of ophiolitic assemblage comprising serpentinite and talc carbonate, listwenite, metagabbro/amphibolite and metabasalt and island arc assemblages. The orogenic gold deposits in the Haimur area occur in the form of smoky/white sulphide-bearing quartz / quartz-carbonate veins or lenses cutting through the listwenite zone-related rocks. The NE-trending auriferous veins were formed due to an extensional to transtensional shearing related to NW Najd shear tectonics. Gold was observed in association with late-pyrite and chalcopyrite paragenetically formed in the gold phase (second phase), while the first phase is the sulphide phase including early-pyrite and arsenopyrite. Arsenopyrite was formed during early metamorphic recrystallization at a high-temperature range between 405 and 512 °C. However, gold was formed at lower temperature through retrograde metamorphism. Three types of fluid inclusions have been recognized: aqueous (type-I), mixed aqueous–carbonic (type-II) and hydrocarbonic (type-III). The P–T conditions of trapping were obtained from the isochore lines of intersection between T = 300–320 °C and pressure range of 60–180 MPa. The Haimur gold deposit was supposed to be derived from metamorphic fluids created by dehydration and decarbonation of ophiolitic mélange assemblages and volcano-sedimentary rocks, in which the gold was transported as Au(HS)2– complexes and precipitated in reduced environment. The strong linkage between the deformation and metamorphism triggered gold deposition in structurally favourable sites related to the Najd fault system.

Fluid inclusion study of tin-mineralized greisens and quartz veins in the Penouta apogranite (Orense, Spain)

1991 ◽  
Vol 55 (379) ◽  
pp. 211-223 ◽  
Author(s):  
J. Mangas ◽  
A. Arribas
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusion Study ◽  
Spectroscopic Techniques ◽  
Raman Spectroscopic ◽  
Quartz Veins ◽  
Low Salinity ◽  
Second Stage ◽  
Third Stage ◽  
Inclusion Study ◽  
Homogenization Temperatures

AbstractThe Penouta deposit is associated with a small Hercynian apogranite stock that intrudes Precambrian-Cambrian gneisses of the Ollo de Sapo Formation. Tin ore occurs as disseminations of cassiterite in the apogranite and as greisenized zones and quartz veins which traverse both the alkaline leucogranite and the surrounding metamorphic country rocks.A fluid-inclusion study, utilizing microthermometric, crushing tests and Raman spectroscopic techniques on quartz from an intragranitic vein and a greisen of the host rock, indicates that the evolution of fluids was similar in both samples and occurred in the three main stages: The first stage is characterized by complex CO2 (CO2-N2-CH4-H2S) and complex CO2 aqueous (H2O-NaCl-CO2-N2-CH4-H2S) fluids of low salinity (Tm ice > −6°C), homogenization temperatures between 250 and 410°C homogenization pressures below 900 bars, and thermobarometric trapping conditions with temperatures below 700°C and pressures below 3250 bars. These fluids were probably responsible for the greisenization of the apogranite and wall rocks, and the precipitation of cassiterite. The second stage is represented by low-salinity aqueous solutions (H2O-NaCl) with Tm ice ⩾ −4.5°C, trapped at homogenization temperatures between 110 and 300 °C and homogenization pressures below 100 bars. This stage can be correlated with kaolinization. The third stage is characterized by higher salinity aqueous fluids (Tm ice ⩾ −16.5°C) containing Na+ and other cations, trapped at homogenization temperatures between 100 and 130°C and homogenization pressures below 5 bars. These fluids can be associated with the epigenetic or supergene phases of the orebody.

scholarly journals Fluid-inclusion studies of high-grade metamorphic rocks of the Ashuanipi complex, eastern Superior Province: constraints on the retrograde P–T path and implications for gold metallogeny

1992 ◽  
Vol 29 (10) ◽  
pp. 2309-2327 ◽  
Author(s):  
Robert P. Moritz ◽  
Serge R. Chevé
Keyword(s):  
High Temperature ◽  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
High Salinity ◽  
Aqueous Fluid ◽  
Metamorphic Rocks ◽  
Gold Deposition ◽  
High Grade ◽  
Low Salinity ◽  
T Path

The high-grade metamorphic rocks of the Ashuanipi complex have been the subject of a microthermometric fluid-inclusion study. Four types of fluid inclusions were observed: CO2-rich fluids; low-temperature, high-salinity H2O fluids; CH4 ± N2-rich fluids; and high-temperature, low-salinity H2O fluids. The regionally distributed CO2-rich fluids are the earliest fluids, and their calculated isochores indicate a clockwise post-peak metamorphic P–T–t path for the Ashuanipi complex. The low-temperature, high-salinity aqueous fluid inclusions are also distributed regionally and can be interpreted as late brines, retrograde metamorphic fluids, or the wicked-off aqueous component of H2O–CO2 fluid inclusions. Both CH4 ± N2-rich fluids and the high-temperature, low-salinity aqueous fluid inclusions were found only locally in gold-bearing metamorphosed banded iron formations. Fluid-inclusion microthermometry, arsenopyrite thermometry, and metamorphic petrologic study at Lac Lilois, one of the principal gold showings, suggest that some gold deposition may have occurred during regional post-peak metamorphic exhumation and cooling at P–T conditions near the amphibolite–greenschist transition. However, it is possible that gold deposition began at higher near-peak metamorphic P–T conditions. Another major gold showing, Arsène, is characterized by CH4 ± N2-rich fluid inclusions, tentatively inferred to be either directly related to gold deposition or responsible for secondary gold enrichment. The association of CH4 ± N2-rich fluids with gold occurrences in the Ashuanipi complex is comparable to gold deposits of the Abitibi greenstone belt and of Wales, Finland, and Brazil.

Fluid inclusion 40Ar/39Ar geochronology of andalusite from syn-tectonic quartz veins: perspectives on dating regional deformation and metamorphism events

2021 ◽  
Author(s):  
Ming Xiao ◽  
Ying-De Jiang ◽  
Hua-Ning Qiu ◽  
Guo-Chun Zhao
Keyword(s):  
Fluid Inclusion ◽  
Thermal Evolution ◽  
Basic Research ◽  
Orogenic Belt ◽  
International Partnership ◽  
Quartz Veins ◽  
Step Heating ◽  
Stepwise Crushing ◽  
Regional Tectonic ◽  
Ar Geochronology

<p>A long-lasting orogenic process often generates vast complexity of deformation and metamorphism. Understanding the time scales of these processes is essential for the reconstruction of the finite architecture of a fossil orogenic belt, which, nevertheless, is not always straightforward. This is because multiple episodes of tectonic events would lead to multiple growth periods of accessory minerals and deformation of rock-forming minerals, which brings challenges for conventional dating methods such as U–Pb, K/Ar, and <sup>40</sup>Ar/<sup>39</sup>Ar step-heating. Fortunately, the emplacement of syn-tectonic quartz veins witness the deformation process and potentially, the associated metamorphism. They, therefore, have the potential to provide vital age information for regional crustal evolution. These veins, especially those in metapelitic terranes, usually contain andalusite, a fluid inclusion bearing K-poor pure aluminosilicate, which stands a good chance for directly dating syn-tectonic veining events by the fluid inclusion <sup>40</sup>Ar/<sup>39</sup>Ar stepwise crushing technique.</p><p>Combined with detailed petro-structural investigation, this study applies the fluid inclusion <sup>40</sup>Ar/<sup>39</sup>Ar geochronology, for the first time, on andalusite minerals in syn-tectonic quartz veins from the Chinese Altai Orogenic Belt, Central Asia, to explore a new way for dating deformation and metamorphism. <sup>40</sup>Ar/<sup>39</sup>Ar stepwise crushing on three andalusite samples yielded well-defined Early Permain ages of 282–274 Ma. These ages are consistent with previously published emplacement ages of regional syn-tectonic leucosome/pegmatite/granite veins and metamorphic ages for local and region schist/gneiss from the same metamorphic series. These results collectively suggest that the fluid inclusion <sup>40</sup>Ar/<sup>39</sup>Ar geochronology of andalusite in syn-tectonic quartz veins has the potential to constrain the timing of fluid-present deformation and potentially contemporaneous metamorphism. This work, therefore, provides a novel way for the age constraints of regional tectonic-thermal evolution of metapelitic terranes in general.</p><p><strong>Acknowledgements </strong></p><p>This project was supported by the Guangdong Basic and Applied Basic Research Foundation (No. 2019A1515012190), the International Partnership Program of Chinese Academy of Sciences (No. 132744KYSB20190039) and the Projects funded by China Postdoctoral Science Foundation (No. 2019M663133). A Guangdong Special Support Program to Y.D. Jiang is also acknowledged.</p>

scholarly journals Easily altered minerals and reequilibrated fluid inclusions provide extensive records of fluid and thermal history: gypsum pseudomorphs of the Tera Group, Tithonian-Berriasian, Cameros Basin

2012 ◽  
Vol 4 (2) ◽  
Author(s):  
Laura González-Acebrón ◽  
Robert Goldstein ◽  
Ramon Mas ◽  
Jose Arribas
Keyword(s):  
Fluid Inclusions ◽  
Thermal History ◽  
Isotopic Analysis ◽  
Northern Spain ◽  
Quartz Veins ◽  
Cameros Basin ◽  
Complex Fluid ◽  
Higher Temperature ◽  
Homogenization Temperatures ◽  
Lower Temperature

AbstractThis study reports a complex fluid and thermal history using petrography, electron microprobe, isotopic analysis and fluid inclusions in replacement minerals within gypsum pseudomorphs in Tithonian-Berriasian lacustrine deposits in Northern Spain. Limestones and dolostones, formed in the alkaline lakes, contain lenticularly shaped gypsum pseudomorphs, considered to form in an evaporative lake. The gypsum was replaced by quartz and non-ferroan calcite (Ca-2), which partially replaces the quartz. Quartz contains solid inclusions of a preexisting non-ferroan calcite (Ca-1), anhydrite and celestine.High homogenization temperatures (T h) values and inconsistent thermometric behaviour within secondary fluid inclusion assemblages in quartz (147–351°C) and calcite (108–352°C) indicate high temperatures after precipitation and entrapment of lower temperature FIAs. Th are in the same range as other reequilibrated fluid inclusions from quartz veins in the same area that are related to Cretaceous hydrothermalism.Gypsum was replaced by anhydrite, likely during early burial. Later, anhydrite was partially replaced by Ca-1 associated with intermediate burial temperatures. Afterward, both anhydrite and Ca-1 were partially replaced by quartz and this by Ca-2. All were affected during higher temperature hydrothermalism and a CO2-H2O fluid. Progressive heating and hydrothermal pulses, involving a CO2-H2O fluid, produce the reequilibration of the FIAs, which was followed by uplift and cooling.

scholarly journals Precious Metal Enrichment at the Myra Falls VMS Deposit, British Columbia, Canada

Geosciences ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 422
Author(s):  
Daniel Marshall ◽  
Carol-Anne Nicol ◽  
Robert Greene ◽  
Rick Sawyer ◽  
Armond Stansell ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Precious Metal ◽  
Metal Enrichment ◽  
Sea Floor ◽  
North West ◽  
Low Salinity ◽  
Volcanogenic Massive Sulphide ◽  
Igneous Fluids ◽  
Homogenization Temperatures ◽  
Water Depths

Gold, present as electrum, in the Battle Gap, Ridge North-West, HW, and Price deposits at the Myra Falls mine, occurs in late veinlets cutting the earlier volcanogenic massive sulphide (VMS) lithologies. The ore mineral assemblage containing the electrum comprises dominantly galena, tennantite, bornite, sphalerite, chalcopyrite, pyrite, and rarely stromeyerite, and is defined as an Au-Zn-Pb-As-Sb association. The gangue is comprised of barite, quartz, and minor feldspathic volcanogenic sedimentary rocks and clay, comprised predominantly of kaolinite with subordinate illite. The deposition of gold as electrum in the baritic upper portions of the sulphide lenses occurs at relatively shallow water depths beneath the sea floor. Primary, pseudosecondary, and secondary fluid inclusions, petrographically related to gold, show boiling fluid inclusion assemblages in the range of 123 to 173 °C, with compositions and eutectic melt temperatures consistent with seawater at approximately 3.2 wt % NaCl equivalent. The fluid inclusion homogenization temperatures are consistent with boiling seawater corresponding to water depths ranging from 15 to 125 m. Slightly more dilute brines corresponding to salinities of approximately 1 wt % NaCl indicate that there is input from very low-salinity brines, which could represent a transition from subaqueous VMS to epithermal-like conditions for precious metal enrichment, mixing with re-condensed vapor, or very low-salinity igneous fluids.

scholarly journals Genesis of the Longmendian Ag–Pb–Zn Deposit in Henan (Central China): Constraints from Fluid Inclusions and H–C–O–S–Pb Isotopes

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-21
Author(s):  
Xinglin Chen ◽  
Yongjun Shao ◽  
Chunkit Lai ◽  
Cheng Wang
Keyword(s):  
Fluid Inclusions ◽  
Central China ◽  
Granitic Magma ◽  
Two Phase ◽  
Quartz Veins ◽  
The North ◽  
Granitic Magmatism ◽  
Polymetallic Sulfides ◽  
Homogenization Temperatures ◽  
Stage 1

The Longmendian Ag–Pb–Zn deposit is located in the southern margin of the North China Craton, and the mineralization occurs mainly in quartz veins, altered gneissic wallrocks, and minor fault breccias in the Taihua Group. Based on vein crosscutting relations, mineral assemblages, and paragenesis, the mineralization can be divided into three stages: (1) quartz–pyrite, (2) quartz–polymetallic sulfides, and (3) quartz–carbonate–polymetallic sulfides. Wallrock alteration can be divided into three zones, i.e., chlorite–sericite, quartz–carbonate–sericite, and silicate. Fluid inclusions in all Stage 1 to 3 quartz are dominated by vapor-liquid two-phase aqueous type (W-type). Petrographic and microthermometric analyses of the fluid inclusions indicate that the homogenization temperatures of Stages 1, 2, and 3 are 198–332°C, 132–260°C, and 97–166°C, with salinities of 4.0–13.3, 1.1–13.1, and 1.9–7.6 wt% NaCleqv, respectively. The vapor comprises primarily H2O, with some CO2, H2, CO, N2, and CH4. The liquid phase contains Ca2+, Na+, K+, SO42−, Cl−, and F−. The sulfides have δ34S=–1.42 to +2.35‰ and 208Pb/204Pb=37.771 to 38.795, 207Pb/204Pb=15.388 to 15.686, and 206Pb/204Pb=17.660 to 18.101. The H–C–O–S–Pb isotope compositions indicate that the ore-forming materials may have been derived from the Taihua Group and the granitic magma. The fluid boiling and cooling and mixing with meteoric water may have been critical for the Ag–Pb–Zn ore precipitation. Geological and geochemical characteristics of the Longmendian deposit indicate that the deposit is best classified as medium- to low-temperature intermediate-sulfidation (LS/IS) epithermal-type, related to Cretaceous crustal-extension-related granitic magmatism.

scholarly journals Fluid Inclusion and Oxygen Isotope Constraints on the Origin and Hydrothermal Evolution of the Haisugou Porphyry Mo Deposit in the Northern Xilamulun District, NE China

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-19 ◽  
Author(s):  
Qihai Shu ◽  
Yong Lai
Keyword(s):  
Fluid Inclusion ◽  
Meteoric Water ◽  
Early Time ◽  
Low Oxygen ◽  
Potassic Alteration ◽  
Low Salinity ◽  
Oxygen Isotopic ◽  
Homogenization Temperatures ◽  
Porphyry Mo Deposit ◽  
Positive Correlations

The Haisugou porphyry Mo deposit is located in the northern Xilamulun district, northeastern China. Based on alteration and mineralization styles and crosscutting relationships, the hydrothermal evolution in Haisugou can be divided into three stages: an early potassic alteration stage with no significant metal deposition, a synmineralization sericite-chlorite alteration stage with extensive Mo precipitation, and a postmineralization stage characterized by barren quartz and minor calcite and fluorite. The coexistence of high-salinity brine inclusions with low-salinity inclusions both in potassic alteration stage (~440°C) and locally in the early time of mineralization stage (380–320°C) indicates the occurrence of fluid boiling. The positive correlations between the homogenization temperatures and the salinities of the fluids and the low oxygen isotopic compositions (δ18Ofluid < 3‰) of the syn- to postmineralization quartz together suggest the mixing of magmatic fluids with meteoric water, which dominated the whole mineralization process. The early boiling fluids were not responsible for ore precipitation, whereas the mixing with meteoric water, which resulted in temperature decrease and dilution that significantly reduced the metal solubility, should have played the major role in Mo mineralization. Combined fluid inclusion microthermometry and chlorite geothermometer results reveal that ore deposition mainly occurred between 350 and 290°C in Haisugou.

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