The Jalilabad copper deposit in the Tarom-Hashjin magmatic belt, NW Iran:Epithermal or porphyry deposit? Evidence from geology, alteration, geochemistry, fluid inclusions, and stable isotope studies

ترکیب سیالات گرمابی در کانسار مس پورفیری کهنگ (شمال شرق اصفهان) با کمک دادههای کانه نگاری، سیالات درگیر و ایزوتوپ های پایدار

Fluid inclusion and stable isotope study of the Lubin-Zardeh epithermal Cu-Au deposit in Zanjan Province, NW Iran: Implications for ore genesis

Preliminary geological work on samples from Davdar in China indicate that emerald occurs in quartz veins hosted within upper greenschist grade Permian metasedimentary rocks including quartzite, marble, phyllite and schist. Fluid inclusion studies indicate highly saline fluids ranging from approximately 34 to 41 wt.% NaCl equivalent, with minimal amounts of CO2 estimated at a mole fraction of 0.003. Fluid inclusion, stable isotope and petrographic studies indicate the Davdar emeralds crystallized from highly saline brines in greenschist facies conditions at a temperature of ∼350°C and a pressure of up to 160 MPa. The highly saline fluid inclusions in the emeralds, the trace-element chemistry and stable isotope signatures indicate that the Davdar emeralds have some similarities to the Khaltaro and Swat Valley emerald deposits in Pakistan, but they show the greatest similarity to neighbouring deposits at Panjshir in Afghanistan.

The Rosita Hills volcanic centre is an alkalicalcic, mid-Tertiary complex overlying orthoand paragneissic basement, on the eastern margin of the Rio Grande Rift in south central Colorado, USA. The centre contains vein-hosted, adularia-sericite type, epithermal Ag and base-metal mineralisation with minor Au. Stable isotope studies (O and H) of whole rock and mineral separate (quartz and sericite) samples from veins and hydrothermal eruption breccias show that the hydrothermal fluid had both magmatic and meteoric components. The δD and δ18O values of the hydrothermal fluid, calculated from mineral values, range from -22‰ to -103‰ and 0.5‰ to 5.9‰ respectively. Fluid inclusion data from vein minerals (quartz, baryte and sphalerite) and from an advanced argillic lithocap overlying the veins again show that the hydrothermal system had more than one component fluid. Fluid inclusions have salinities which range from 1.7 to 25.1 wt% NaCl equivalent and show evidence of boiling in the advanced argillic lithocap. Homogenisation temperatures range from 135°C to 298°C. Liquid CO2 is present in some inclusions. These data indicate that a saline, isotopically heavy fluid mixed with a dilute, isotopically light fluid to precipitate the ore. We argue that the saline, isotopically heavy fluid is magmatic and derived from a resurgent rhyolitic magma below the mineralisation.

Metalliferous (Fe–Cu–Pb–Zn) quartz–carbonate–sulphide veins cut greenschist to epidote–amphibolite facies metamorphic rocks of the Dalradian, SW Scottish Highlands, with NE–SW to NW–SE trends, approximately parallel or perpendicular to regional structures. Early quartz was followed by pyrite, chalcopyrite, sphalerite, galena, barite, late dolomite–ankerite and clays. Both quartz–sulphide and carbonate vein mineralisation is associated with brecciation, indicating rapid release of fluid overpressure and hydraulic fracturing.Two distinct mineralising fluids were identified from fluid inclusion and stable isotope studies. High temperature (>350°C) quartz‐precipitating fluids were moderately saline (4.0–12.7 wt.% NaCl equivalent) with low (approximately 0.05). Quartz δ18O (+11.7 to +16.5‰) and sulphide δ34S (−13.6 to −1.1‰) indicate isotopic equilibrium with host metasediments (rock buffering) and a local metasedimentary source of sulphur. Later, low‐temperature (TH = 120–200°C) fluids, probably associated with secondary carbonate, barite and clay formation, were also moderately saline (3.8–9.1 wt.% NaCl equivalent), but were strongly enriched in 18O relative to host Dalradian lithologies, as indicated by secondary dolomite–ankerite (δ18O = +17.0 to +29.0‰, δ13C = −1.0 to −3.0‰). Compositions of carbonate–forming fluids were externally buffered.The veins record the fluid–rock interaction history of metamorphic host rocks during cooling, uplift and later extension. Early vein quartz precipitated under retrograde greenschist facies conditions from fluids probably derived by syn‐metamorphic dehydration of deeper, higher‐grade rocks during uplift and cooling of the Caledonian metamorphic complex. Veins are similar to those of mesothermal veins in younger Phanerozoic metamorphic belts, but are rare in the Scottish Dalradian. Early quartz veins were reactivated by deep penetration of low‐temperature basin fluids that precipitated carbonate and clays in veins and adjacent Dalradian metasediments throughout the SW Highlands, probably in the Permo‐Carboniferous. This event is consistent with paragenetically ambiguous barite with δ34S characteristic of late Palaeozoic basinal brines.

Geothermal systems ancient and modern: a geochemical review

Geology, fluid inclusion and stable isotope study of the Yueyang Ag-Au-Cu deposit, Zijinshan orefield, Fujian Province, China

Stable isotope (S, O, H and C) studies of the phyllic and potassic–phyllic alteration zones of the porphyry copper deposit at Sungun, East Azarbaidjan, Iran

The Vilalba gold district, a new discovery in the Variscan terranes of the NW of Spain: A geologic, fluid inclusion and stable isotope study

An integrated fluid inclusion and stable isotope study was carried out on hydrothermal veins (Sb‐bearing quartz veins, metal‐bearing fluorite–barite–quartz veins) from the Schwarzwald district, Germany. A total number of 106 Variscan (quartz veins related to Variscan orogenic processes) and post‐Variscan deposits were studied by microthermometry, Raman spectroscopy, and stable isotope analysis. The fluid inclusions in Variscan quartz veins are of the H2O–NaCl–(KCl) type, have low salinities (0–10 wt.% eqv. NaCl) and high Th values (150–350°C). Oxygen isotope data for quartz range from +2.8‰ to +12.2‰ and calculated δ18OH2O values of the fluid are between −12.5‰ and +4.4‰. The δD values of water extracted from fluid inclusions vary between −49‰ and +4‰. The geological framework, fluid inclusion and stable isotope characteristics of the Variscan veins suggest an origin from regional metamorphic devolatilization processes.By contrast, the fluid inclusions in post‐Variscan fluorite, calcite, barite, quartz, and sphalerite belong to the H2O–NaCl–CaCl2 type, have high salinities (22–25 wt.% eqv. NaCl) and lower Th values of 90–200°C. A low‐salinity fluid (0–15 wt.% eqv. NaCl) was observed in late‐stage fluorite, calcite, and quartz, which was trapped at similar temperatures. The δ18O values of quartz range between +11.1‰ and +20.9‰, which translates into calculated δ18OH2O values between −11.0‰ and +4.4‰. This range is consistent with δ18OH2O values of fluid inclusion water extracted from fluorite (−11.6‰ to +1.1‰). The δD values of directly measured fluid inclusion water range between −29‰ and −1‰, −26‰ and −15‰, and −63‰ and +9‰ for fluorite, quartz, and calcite, respectively.Calculations using the fluid inclusion and isotope data point to formation of the fluorite–barite–quartz veins under near‐hydrostatic conditions. The δ18OH2O and δD data, particularly the observed wide range in δD, indicate that the mineralization formed through large‐scale mixing of a basement‐derived saline NaCl–CaCl2 brine with meteoric water. Our comprehensive study provides evidence for two fundamentally different fluid systems in the crystalline basement. The Variscan fluid regime is dominated by fluids generated through metamorphic devolatilization and fluid expulsion driven by compressional nappe tectonics. The onset of post‐Variscan extensional tectonics resulted in replacement of the orogenic fluid regime by fluids which have distinct compositional characteristics and are related to a change in the principal fluid sources and the general fluid flow patterns. This younger system shows remarkably persistent geochemical and isotopic features over a prolonged period of more than 100 Ma.

Geology, fluid inclusion and isotope constraints on ore genesis of the post-collisional Dabu porphyry Cu–Mo deposit, southern Tibet

A fluid inclusion and stable isotopic study has been undertaken on some massive sulphide deposits (Aguas Tenidas Este, Concepcion, San Miguel, San Telmo and Cueva de la Mora) located in the northern Iberian Pyrite Belt. The isotopic analyses were mainly performed on quartz, chlorite, carbonate and whole rock samples from the stockworks and altered footwall zones of the deposits, and also on some fluid inclusion waters. Homogenization temperatures of fluid inclusions in quartz mostly range from 120 to 280 °C. Salinity of most fluid inclusions ranges from 2 to 14 wt% NaCl equiv. A few cases with Th=80–110 °C and salinity of 16–24 wt% NaCl equiv., have been also recognized. In addition, fluid inclusions from the Soloviejo Mn–Fe-jaspers (160–190 °C and ≈6 wt% NaCl equiv.) and some Late to Post-Hercynian quartz veins (130–270 °C and ≈4 wt% NaCl equiv.) were also studied. Isotopic results indicate that fluids in equilibrium with measured quartz (δ18Ofluid ≈–2 to 4‰), chlorites (δ18Ofluid ≈8–14‰, δDfluid ≈–45 to –27‰), whole rocks (δ18Ofluid ≈4–7‰, δDfluid ≈–15 to –10‰), and carbonates (δ18Oankerite ≈14.5–16‰, δ13Cfluid =–11 to –5‰) evolved isotopically during the lifetime of the hydrothermal systems, following a waxing/waning cycle at different temperatures and water/rock ratios. The results (fluid inclusions, δ18O, δD and δ13C values) point to a highly evolved seawater, along with a variable (but significant) contribution of other fluid reservoirs such as magmatic and/or deep metamorphic waters, as the most probable sources for the ore-forming fluids. These fluids interacted with the underlying volcanic and sedimentary rocks during convective circulation through the upper crust.

Porphyry deposits and oxidized magmas

We review the major stable carbon and nitrogen isotope studies conducted on human remains in the North American Arctic (NAA) and discuss the findings with respect to two major research themes: diachronic subsistence, and the development of food cultures across the NAA. The interpretation of stable isotope data from human bone collagen and hair keratin is complicated by issues of equifinality in addition to uncertainty arising from the high fat/high protein diets of Arctic hunter gatherers. We suggest future lines of inquiry which may help to alleviate some of these challenges. Our review of Arctic stable isotope studies shows the ongoing potential of stable isotope analysis of Arctic hunter-gatherers and faunal populations, but we include the caveat that regardless of how cutting-edge or refined the analytical method, future stable isotope studies must be contextualized with other lines of evidence from well-excavated sites, and would profoundly benefit from the incorporation of indigenous perspectives and research priorities.

A genetic model for a mesothermal Au deposit: evidence from fluid inclusions and stable isotopic studies at El Sid Gold Mine, Eastern Desert, Egypt