Fluid-inclusion evidence of basinal brines in Archean basement, Thunder Bay Pb–Zn–Ba district, Ontario, Canada

1988 ◽  
Vol 25 (11) ◽  
pp. 1884-1894 ◽  
Author(s):  
Frederick M. Haynes
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Ore Deposits ◽  
Temperature Phase ◽  
Type I ◽  
Mississippi Valley ◽  
Thunder Bay ◽  
Calcite Veins ◽  
Archean Basement ◽  
Liquid Vapor

Fluid inclusions from three quartz–galena–sphalerite–barite–calcite veins in the Thunder Bay district of western Ontario contain liquid + vapor ± halite and homogenize by vapor disappearance or halite dissolution at temperatures of 90–200 °C. Cyclically frozen, liquid + vapor (type I) inclusions undergo four melting events upon gradual warming (initial melting at −55 to −46 °C; ice disappearance at −30.2 to −25.4 °C; inversion of hydrohalite to halite at −8.0 to 0.7 °C; and halite melting at 14.0 to 56.3 °C. Liquid + vapor + halite (type II) inclusions behave similarly but have higher Tm ice (−27.2 to −21.7 °C) and Tm halite (105–203 °C). Scanning electron microscopy and energy dispersive analysis of fluid-inclusion-derived decrepitates indicate that the solutes consist of NaCl > CaCl2 [Formula: see text] KCl and are consistent with the low-temperature phase observations in that they define two distinct populations based on CaCl2/(CaCl2 + NaCl) ratios.The temperatures and compositional trends defined by the inclusion results are similar to those documented for basinal brines and from fluid inclusions in Mississippi Valley type ore deposits. The Thunder Bay veins cross the basal unconformity of the Middle Proterozoic Sibley basin and extend into Archean basement granites, such that the fluid inclusions results provide direct evidence that basinal waters infiltrated basement rock in western Ontario. The inclusion fluids and associated mineralization are thought to result either from dewatering of the Sibley basin during Keweenaw age rifting or from the introduction of exotic Paleozoic basinal waters when the Michigan basin extended over the region.

Application of combined fluid-inclusion and clumped isotope thermometry to biogenic and inorganic carbonates

2021 ◽  
Author(s):  
Jeroen van der Lubbe ◽  
Cas Nooitgedacht ◽  
Philip Staudigel ◽  
Martin Ziegler
Keyword(s):  
Fluid Inclusion ◽  
Oxygen Isotope ◽  
High Temperatures ◽  
Fluid Inclusions ◽  
Isotope Composition ◽  
A Priori ◽  
Calcium Carbonates ◽  
Oxygen Isotope Exchange ◽  
Calcite Veins ◽  
Clumped Isotope

<p>Biogenic and inorganic carbonates are widely used to reconstruct past temperatures and fluid compositions. For decades, calcification temperatures have been inferred from oxygen isotope composition (δ<sup>18</sup>O) of calcium carbonates (CaCO­<sub>3</sub>) assuming the δ<sup>18</sup>O of the parental fluid and isotopic equilibrium precipitation conditions. The development of the clumped isotope (Δ<sub>47</sub>) thermometer allows for reconstructing equilibrium calcification temperatures without requiring a priori knowledge of the water δ<sup>18</sup>O values.</p><p>Carbonate minerals can also contain several weight percentages of water, which are typically trapped within microscopic pores. These fluid-inclusions may preserve remnants of the parental fluid, which can be analyzed for the δ<sup>18</sup>O as well as hydrogen isotopic (δ<sup>2</sup>H) composition. Subsequently, the δ<sup>18</sup>O of fluid-inclusion and host carbonate may allow for the determination of paleotemperatures by providing constraint on the δ<sup>18</sup>O water value.</p><p>Reasonable equilibrium temperatures can be obtained for speleothem calcites from cave systems. On the contrary, anomalously high temperatures are derived from δ<sup>18</sup>O fluid-inclusion and calcite pairs in soil carbonates possibly suggesting diffusion of trapped water from host CaCO<sub>3</sub>. Deeply-buried and subsequently exhumed (inorganic) calcite veins have yielded discrepant paleotemperature estimates between fluid-inclusion and Δ<sub>47</sub> thermometers. The distinctly lower fluid-inclusion derived temperatures might be attributed to kinetic fraction during initial vein cementation and/or isotopic re-equilibration between fluid-inclusions and CaCO<sub>3</sub> at lower temperatures during uplift.</p><p>Heating experiments demonstrate that the oxygen isotope exchange between fluid inclusions and host carbonate is limited for inorganic calcite and aragonite at high temperatures (175<sup>o</sup>C) for short timescales (90 minutes). In contrast, considerable positive shifts in the δ<sup>18</sup>O of fluid inclusions have been recorded in biogenic aragonites during experimental heating, which coincide with lower carbonate δ<sup>18</sup>O values (albeit to a lesser extent due to the overwhelming amount of oxygen in the CaCO<sub>3</sub>), indicative of re-equilibration between host carbonate and pore fluids. This effect leads to apparently high equilibrium temperatures. In conjunction, the Δ<sub>47</sub> derived temperatures do not change significantly after heating of inorganic aragonite, whereas a considerable higher Δ<sub>47</sub> temperature is derived from aragonitic bivalve samples after heating. The positive shift in both thermometers has interpreted to reflect re-crystallization of CaCO<sub>3</sub> and isotopic re-equilibration between the host carbonate and fluid-inclusions. This exchange might be facilitated by extremely small fluid-inclusions present in biogenic carbonates and/or water associated with organic substances.</p><p>Importantly, these isotopic exchange processes in biogenic aragonites took place in the absence of an external fluid and below the temperature thresholds for solid-state-reordering and the aragonite-to-calcite transition. The novel application of combined fluid-inclusion and clumped isotope thermometry has a proven utility in determining equilibrium precipitation temperatures, monitoring preservation of the primary fluid-inclusions and re-crystallization processes during diagenesis. However, additional experiments and analytical improvements are needed to further constrain the diagenetic behavior of this proxy.</p><p> </p>

scholarly journals Fluid inclusion study of shear zone hosted lode gold type deposits: El Bagre mining district, Antioquia-Colombia

2020 ◽  
Vol 24 (3) ◽  
pp. 245-257
Author(s):  
Edwin Naranjo Sierra ◽  
Mauricio Alvaran Echeverri
Keyword(s):  
Fluid Inclusion ◽  
Shear Zone ◽  
Gold Deposits ◽  
Fluid Inclusion Study ◽  
Mining District ◽  
Type I ◽  
Lode Gold ◽  
Calcite Veins ◽  
Inclusion Study ◽  
Homogenization Temperatures

The shear zone hosted lode gold type deposits are located at the northeast part of Antioquia department of Colombia. The characteristics of ore-forming fluids were discussed using fluid inclusion petrography and microthermometry analysis. Two stages, namely quartz-pyrite pre-mineralization stage (1) and reactivation-sulfides-tellurides mineralization stage (2) were included in this study. Two types of fluid inclusions were observed: primary aqueous-carbonic inclusions (type I) are characterized by the presence of clathrate, with salinities between 1.5 and 8.3 %wt NaCl equiv. and homogenization temperatures (to liquid) occurs between 238.1° and 297.1°C. Secondary aqueous inclusions (type II) were trapped in reactivated quartz (type IIa) and cross-cutting calcite veins (type IIb), salinity estimates display a mixing trend from a relatively saline with 9.21 %wt NaCl member (type IIa) to a low salinity one with 3.82 %wt NaCl (type IIb), homogenizations to a liquid phase occur between 150.8° and 184.6°C for type IIa inclusions and 130.3° to 190.4°C for type IIb. Based on these results, the shear zone hosted lode gold type deposits from El Bagre mining district, share similar characteristics with orogenic gold deposits.

scholarly journals Prediction of Mississippi-Valley type ore fluid metal concentrations from solid solution metal concentrations in ore-stage minerals

2017 ◽  
Author(s):  
◽  
Sarah Smith
Keyword(s):  
Solid Solution ◽  
Fluid Inclusion ◽  
Distribution Coefficient ◽  
Fluid Inclusions ◽  
Mississippi Valley ◽  
Carbonate Minerals ◽  
Metal Concentrations ◽  
Fluid Inclusion Data ◽  
Mvt Deposits ◽  
Mississippi Valley Type

Mississippi-Valley-type (MVT) deposits have some of the greatest enrichments of Pb, Zn, Ba, and F in the Earth's crust. Fundamental to understanding how these elements were transported and precipitated to form MVT deposits is knowledge of their concentrations in the ore fluids. Recent research aimed at determining the concentrations of Pb, Zn, and Ba in the ore fluids that formed the MVT deposits of the U.S. midcontinent, the type examples for the MVT deposit class, has focused on using LA-ICPMS to analyze fluid inclusions. This research has shown U.S. mid-continent MVT ore fluids to have Ba concentrations on the order of 10's of ppm. However, LA-ICP-MS results for Pb and Zn concentrations are equivocal due to interferences from Zn and Pb in the host mineral matrix and uncertainties about whether the measured Pb and Zn signals represent aqueous solute or "accidentals", i.e. Pb or Zn solid particulates entrained within the fluid inclusions. In light of these limitations, this study sought to determine metal concentrations in MVT ore fluids instead by calculating them theoretically based on their solid solution concentrations in the ore-stage minerals calcite and galena. Using experimental partition coefficients from Rimstidt et al. (1998) at ore stage temperatures and measured compositions of ore-stage calcite from the Illinois-Kentucky and Central Tennessee MVT districts, concentrations of Mg, Mn, Fe, Zn, Sr, Ba, and Pb in the ore fluid were predicted. The predicted ore fluid concentrations of Mg and Mn, which form carbonate minerals (magnesite and rhodochrosite) with the calcite structure, were in good agreement with available fluid inclusion data for these elements. Thus, the predicted ore fluid concentrations of Zn and Fe, which also form carbonate minerals (smithsonite and siderite) with the calcite structure, 10s of ppm Zn and 1s to 10s of ppm Fe in Illinois-Kentucky and a maximum of 10s of ppm Zn and 1s to 10s of ppm Fe in Central Tennessee , are likely to be accurate. These Zn concentrations are typical of modern sedimentary brines and high enough to allow efficient Zn ore formation. In contrast, the predicted ore fluid concentrations of Sr and Ba, which form carbonate minerals (strontianite and witherite) with the aragonite structure, were in poor agreement with available fluid inclusion data for these elements. Thus, the predicted 1s of ppm ore fluid concentration of Pb, which also forms a carbonate mineral (cerussite) with the aragonite structure, is unlikely to be accurate. Using predicted thermodynamic data (Sverjensky, 1985) for ZnS with the galena structure, a thermodynamic distribution coefficient for Zn between aqueous solution and solid solution in galena was calculated. This distribution coefficient was used in combination with Zn concentrations measured in solid solution in galena from the Central Missouri, Central Tennessee, Illinois-Kentucky, Northern Arkansas, Tri-State, and Southeast Missouri MVT districts to predict Zn/Pb ratios for the ore fluids. The Zn/Pb ratios do not agree with the ore Zn/Pb ratios of the districts and appear to be an artifact of the temperature used in the calculations. Therefore the predicted ore fluid Zn/Pb ratios are unlikely to be correct.

scholarly journals Fluid Inclusions and Rare Earth Elements (REE) analysis in calcite veins: Tectonic - diagenesis interaction in the Rosablanca formation, Mesa de los Santos sector, eastern cordillera, Colombia

2018 ◽  
Vol 8 (1) ◽  
pp. 31-43 ◽  
Author(s):  
Jairo Conde-Gómez
Keyword(s):  
Rare Earth ◽  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Early Event ◽  
Fluid Circulation ◽  
Carbonate Cement ◽  
Diagenetic Processes ◽  
Calcite Veins ◽  
Different Types ◽  
Immiscible Mixture

Studies conducted by means of petrography, cathodoluminescence, SEM, fluid inclusion and REE geochemistry in core samples from the Rosablanca Formation in the Mesa de Los  Santos sector, identified two types of material: the host rock classified as Packstones and Grainstones, and veins that texturally expose three types of filling (blocky texture, blocky elongate texture, fibrous texture). Diagenesis is characterized by dissolution, carbonate cement precipitation, compaction, fracturing and fluid circulation through fractures during at least three episodes; these diagenetic processes were contemporaneous with the distensive and compressive tectonic regimes regionally dominant during the Cretaceous, Paleogene and Neogene in the study area. The fluids that generated the different types of texture inside the veins were brines that belonged to the H2O – NaCl – CaCl2 system, with salinities between 0.03 – 12.96 % wt eq NaCl, derived from the Rosablanca Formation that was deposited under oxic conditions, retaining their marine character and implying an autochthonousorigin for the REE present in the veins. The conditions of entrapment for fluid inclusions during the early event were heterogeneous, arising from an immiscible mixture of brines andhydrocarbons, while in the second, they were homogeneous with later post-entrapment processes.later post-entrapment processes.

scholarly journals Fluid Evolution and Ore Genesis of the Qibaoshan Polymetallic Ore Field, Shandong Province, China: Constraints from Fluid Inclusions and H–O–S Isotopic Compositions

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 394
Author(s):  
Yu ◽  
Li ◽  
Wang ◽  
Wang
Keyword(s):  
Fluid Inclusion ◽  
Fluid Inclusions ◽  
Meteoric Water ◽  
Ore Deposits ◽  
Shandong Province ◽  
Isotopic Data ◽  
Magmatic Water ◽  
Oxygen Isotopic ◽  
Stage 1 ◽  
Polymetallic Ore

The Qibaoshan polymetallic ore field is located in the Wulian area, Shandong Province, China. Four ore deposits occur in this ore field: the Jinxiantou Au–Cu, Changgou Cu–Pb–Zn, Xingshanyu Pb–Zn, and Hongshigang Pb–Zn deposits. In the Jinxiantou deposit, three paragenetic stages were identified: quartz–pyrite–specularite–gold (Stage 1), quartz–pyrite–chalcopyrite (Stage 2), and quartz–calcite–pyrite (Stage 3). Liquid-rich aqueous (LV type), vapor-rich aqueous (V type), and halite-bearing (S type) fluid inclusions (FIs) are present in the quartz from stages 1–3. Microthermometry indicates that the initial ore-forming fluids had temperatures of 351–397 °C and salinities of 42.9–45.8 mas. % NaCl equivalent. The measured hydrogen and calculated oxygen isotopic data for fluid inclusion water (δ18OFI = 11.1 to 12.3‰; δDFI = −106.3 to −88.6‰) indicates that the ore-forming fluids were derived from magmatic water; then, they were mixed with meteoric water. In the Changgou deposit, three paragenetic stages were identified: quartz–pyrite–specularite (Stage 1), quartz–pyrite–chalcopyrite (Stage 2), and quartz–galena–sphalerite (Stage 3). LV, V, and S-type FIs are present in the quartz from stages 1–3. Microthermometry indicates that the initial ore-forming fluids had temperatures of 286–328 °C and salinities of 36.7–40.2 mas. % NaCl equivalent. The measured hydrogen and calculated oxygen isotopic data for fluid inclusion water (δDFI = −115.6 to −101.2‰; δ18OFI = 12.2 to 13.4‰) indicates that the ore-forming fluids were derived from magmatic water mixed with meteoric water. The characteristics of the Xingshanyu and Hongshigang deposits are similar. Two paragenetic stages were identified in these two deposits: quartz–galena–sphalerite (Stage 1) and quartz–calcite–poor sulfide (Stage 2). Only LV-type FIs are present in the quartz in stages 1–2. The ore-forming fluids had temperatures of 155–289 °C and salinities of 5.6–10.5 mas. % NaCl equivalent. The measured hydrogen and calculated oxygen isotopic data for fluid inclusion water (δDFI = −109.8 to −100.2‰; δ18OFI = 10.2 to 12.1‰) indicates that the ore-forming fluids were derived from circulating meteoric waters. The sulfur isotopes (δ34Ssulfide = 0.6 to 4.3‰) of the four deposits are similar, indicating a magmatic source for the sulfur with minor contributions from the wall rocks. The ore field underwent at least two phases of mineralization according to the chronology results of previous studies. Based on the mineral assemblage and fluid characteristics, we suggest that the late Pb–Zn mineralization was superimposed on the early Cu (–Au) mineralizaton in the Changgou deposit.

scholarly journals Radiogenic Pb Enrichment of Mississippi Valley-Type Metallic Ore Deposits, Southern Ozarks: Constraints Based on Geochemical Studies of Source Rocks and Their Diagenetic History

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 172
Author(s):  
Jonathan Chick ◽  
Sydney E. McKim ◽  
Adriana Potra ◽  
Walter L. Manger ◽  
John R. Samuelsen
Keyword(s):  
Linear Trend ◽  
Ore Deposits ◽  
Source Rocks ◽  
Mississippi Valley ◽  
Isotopic Signatures ◽  
Boone Formation ◽  
Tripolitic Chert ◽  
Geochemical Studies ◽  
Mississippi Valley Type ◽  
Valley Type

Southern Ozark Mississippi Valley-type ores are enriched in radiogenic Pb, with isotopic signatures suggesting that metals were supplied by two end-member components. While the less radiogenic component appears to be derived from various shale and sandstone units, the source of the more radiogenic component has not yet been identified. Analyses of cherts from the Early Ordovician Cotter Dolomite and tripolitic chert from the Early Mississippian Boone Formation contain highly radiogenic Pb, with isotopic ratios comparable to those of ores. However, most samples have lower 208Pb/204Pb and 207Pb/204Pb for a given 206Pb/204Pb compared to ores. These relationships demonstrate that the enriched Pb isotopic values of the ore array cannot be related to the host and regional lithologies sampled, suggesting that the source of high ratios may lay further afield. The slope of the linear trend defined by the Pb isotope ratios of ores corresponds to an age of about 1.19 Ga. Therefore, an alternative for the linear array is the involvement of Precambrian basement in supplying ore Pb. Rare earth element patterns show that diagenetic processes involving the action of groundwater and hydrothermal fluids affected the sampled lithologies to various degrees, with Cotter Dolomite having experienced the highest degree of alteration.

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