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Journal ArticleDOI

Regional Carbonate Alteration of the Crust by Mantle-Derived Magmatic Fluids, Tamil Nadu, South India

01 Jul 1994-The Journal of Geology (University of Chicago Press)-Vol. 102, Iss: 4, pp 379-398
TL;DR: In this paper, carbon, oxygen, and strontium isotope analyses of samples of ankerite and calcite, together with some of the coexisting silicate minerals, have been used to constrain the conditions of formation of the carbonate alteration and the origin of the fluids involved.
Abstract: Regional carbonate alteration of the crust associated with major shear zones provides direct evidence for $CO_{2}$-rich fluid mobility. A good example occurs within the Attur lineament, one of numerous Proterozoic shear zones which crosscut charnockitic gneisses and other lithologies of the southern Indian craton. At this locality, widespread carbonate alteration of silicate rocks has involved growth of ankerite and other carbonate minerals which replace preexisting silicates. Some of the ankerite was subsequently recrystallized to fine-grained calcite and iron oxide, accompanied by sericitization of feldspar. Carbon, oxygen, and strontium isotope analyses of samples of ankerite and calcite, together with some of the coexisting silicate minerals, have been used to constrain the conditions of formation of the carbonate alteration and the origin of the fluids involved. $\delta^{13}C$ values of ankerite are relatively homogeneous, ranging between -6.5 and -3.9 ‰ with a mean of -5.3 ‰. $\delta^{18}O$ is also ...
Citations
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Journal ArticleDOI
TL;DR: In this paper, the authors present results from thermodynamic computations in appropriate petrogenetic systems to quantitatively evaluate CO2 generation from calc-silicate rocks as well as model mantle peridotite, and demonstrate that CO2 release occurs in both cases under the P-T conditions and tectonic settings inferred for the formation of charnockites and ultrahigh-temperature granulites.

151 citations

Journal ArticleDOI
TL;DR: Carbon can be a major constituent of crustal and mantle fluids, occurring both as dissolved ionic species (e.g., carbonate ions or organic acids) and molecular species (i.e., CO2, CO, CH4, and more complex organic compounds) as discussed by the authors.
Abstract: Carbon can be a major constituent of crustal and mantle fluids, occurring both as dissolved ionic species (e.g., carbonate ions or organic acids) and molecular species (e.g., CO2, CO, CH4, and more complex organic compounds). The chemistry of dissolved carbon changes dramatically with pressure ( P ) and temperature ( T ). In aqueous fluids at low P and T , molecular carbon gas species such as CO2 and CH4 saturate at low concentration to form a separate phase. With modest increases in P and T , these molecular species become fully miscible with H2O, enabling deep crustal and mantle fluids to become highly concentrated in carbon. At such high concentrations, carbon species play an integral role as solvent components and, with H2O, control the mobility of rock-forming elements in a wide range of geologic settings. The migration of carbon-bearing crustal and mantle fluids contributes to Earth’s carbon cycle; however, the mechanisms, magnitudes, and time variations of carbon transfer from depth to the surface remain least understood parts of the global carbon budget (Berner 1991, 1994; Berner and Kothavala 2001). Here we provide an overview of carbon in crustal and mantle fluids. We first review the evidence for the presence and abundance of carbon in these fluids. We then discuss oxidized and reduced carbon, both as solutes in H2O-rich fluids and as major components of miscible CO2-CH4-H2O fluids. Our goal is to provide some of the background needed to understand the role of fluids in the deep carbon cycle. ### Carbon in aqueous fluids of crust and mantle Numerous lines of evidence indicate that carbon may be an important component of crustal and mantle fluids. Fluid inclusions provide direct samples of carbon-bearing fluids from a range of environments. Carbon species in fluid …

141 citations

Journal ArticleDOI
TL;DR: In this article, the authors measured the solubility of calcite in NaCl-H 2 O solutions at 600-900 °C, 10kbar, at NaCl concentrations ranging from dilute to near halite saturation, and at 6-14 kbar, 700 °C in 30 mol% NaCl solutions.
Abstract: The solubility of calcite in NaCl-H 2 O solutions was measured at 600–900 °C, 10 kbar, at NaCl concentrations ranging from dilute to near halite saturation, and at 6–14 kbar, 700 °C, in 30 mol% NaCl solutions. Solubility was determined from the weight loss of cleavage rhombs of a pure natural calcite after experiments of 1/2 to 6 days in a piston-cylinder apparatus with NaCl-graphite furnaces. CaCO 3 molality ( m CaCO 3 ) increases greatly with NaCl mole fraction ( X NaCl): at 800 °C and 10 kbar, m CaCO 3 increases from ~0.1 in pure H 2 O to near 4.0 at halite saturation ( X NaCl ~ 0.6). There is also a large temperature effect at 10 kbar, with m CaCO 3 increasing from 0.25 at 600 °C to 3.0 at 900 °C at X NaCl = 0.3. There is only a 20% increase with increasing pressure between 6 and 14 kbar at 700 °C and X NaCl = 0.3. Melting to a carbonate-rich liquid was inferred at 900 °C, 10 kbar, from X NaCl of 0 to 0.2. The composition, temperature, and pressure dependence of m CaCO 3 are described by: \[\mathit{m}_{CaCO_{3}}\ =\ [{-}0.051\ +\ 1.65\ {\times}\ 10^{{-}4}\ \mathit{T}\ +\ \mathit{X}^{2}_{NaCl}exp({-}3.071\ +\ 4.749\ {\times}\ 10^{{-}6}\mathit{T}^{2})]\ (0.76\ +\ 0.024\mathit{P})\] with T in Kelvins and P in kbar. The predicted increase of calcite solubility with salinity and temperature is so great that critical mixing of NaCl-rich hydrous carbonate liquid and CaCO 3 -rich saline solution is probable at 10 kbar near 1000 °C and X NaCl ~ 0.4. The experimental results suggest a genetic mechanism for the enigmatic carbonated shear zones, such as the Attur Valley of southern India, where crustal rocks have been replaced by up to 20% by calcite and ankerite with mantle-like stable-isotope signatures. The high CaCO 3 carrying capacity of concentrated alkali-chloride solutions, together with the drastic decrease in solubility between 1000 and 700 °C, plausibly account for large-scale emplacement of mantle-derived carbonate from concentrated chloride-carbonate solutions (or hydrosaline magmas) formed as immiscible fluids in the late stages of alkalic magmatism. Such solutions may also mobilize sulfate and phosphate minerals, which would have important consequences for redistribution of incompatible and heat-producing elements in the crust.

122 citations


Cites background from "Regional Carbonate Alteration of th..."

  • ...Examples include the post-Hercynian South Tien Shan fault zone (Baratov et al. 1984), the Late Proterozoic Attur Valley of Tamil Nadu, India (Wickham et al. 1994), the Late Archean Chitradurga area of Karnataka, India (Chadwick et al. 1989), the Mid-Proterozoic Mary Kathleen Fold Belt of Queensland, Australia (Oliver et al. 1993), and the Mid-Proterozoic Bamble Shear Belt of southern Norway (Dahlgren et al. 1993)....

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  • ...Examples include the post-Hercynian South Tien Shan fault zone (Baratov et al. 1984), the Late Proterozoic Attur Valley of Tamil Nadu, India (Wickham et al. 1994), the Late Archean Chitradurga area of Karnataka, India (Chadwick et al. 1989), the Mid-Proterozoic Mary Kathleen Fold Belt of…...

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Journal ArticleDOI
TL;DR: In this paper, the authors investigated the role of brines in the deep crust and upper mantle of metamorphic and magmatic systems and provided new insights into fluid-rock interaction in a range of settings.
Abstract: Chloride-rich brines are increasingly recognized as playing an important role in high pressure and temperature metamorphic and magmatic systems. The origins of these saline multicomponent fluids are debated, but experimental evidence suggests that regardless of their origin they must be important agents of rock alteration and mass transfer wherever they occur. Studies of the solubility of quartz in H2O, CO2‐H2O and salt‐H2O solutions provide a framework for understanding the role of brines in the deep crust and upper mantle. While quartz solubility in the system SiO2‐H2O‐NaCl‐CO2 is maximal at a given high pressure and temperature if the solvent is pure H2O, the decline in quartz solubility with NaCl content (salting-out) is less severe than in CO2‐H2O fluids at comparable H2O activities. Moreover, at lower pressures, quartz solubility initially salts in at low salt contents, before reaching a maximum and then declining. The behavior of quartz solubility in salt‐H2O solutions has not yet been fully explained and is the subject of active debate. Experimental investigations of the solubility of some other rock-forming oxides and silicates show enhancements due to NaCl addition. As illustrated by the well-studied CaO‐Al2O3‐SiO2‐NaCl‐H2O system, enhancements initially increase to maxima, and then decline. This behavior can be explained by formation of a range of hydrated aqueous complexes and clusters with specific NaCl:H2O stoichiometries. In contrast, solubilities of calcium salts, including calcite, fluorite, fluorapatite and anhydrite, rise monotonically with increasing NaCl, implying complexing to form anhydrous ionic solutes and⁄or ion pairs. The experimental studies offer new insights into fluid-rock interaction in a range of settings, including carbonatite‐fenite complexes, granulite-facies metamorphism, porphyry ore deposits and aluminum-silicate vein complexes in high-grade metamorphic terranes.

111 citations


Cites background from "Regional Carbonate Alteration of th..."

  • ...Depending on the initial bulk composition, a supercritical carbonatite magma may either split into carbonate-rich and NaCl-rich fractions during cooling (path A), in which case a carbonatite–fenite association may develop, or pass continuously into ultrasaline fluids (path B) capable of voluminous carbonate alteration of country rocks, as in the carbonate-metasomatized megashear zones like the Attur Fault Zone of South India (Wickham et al. 1994)....

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  • ...…(path A), in which case a carbonatite–fenite association may develop, or pass continuously into ultrasaline fluids (path B) capable of voluminous carbonate alteration of country rocks, as in the carbonate-metasomatized megashear zones like the Attur Fault Zone of South India (Wickham et al. 1994)....

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  • ...shear zones like the Attur Fault Zone of South India (Wickham et al. 1994)....

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Journal ArticleDOI
TL;DR: The Late Archean crust south of Krishnagiri, Tamil Nadu, consists of tonalitic-trondhjemitic-granodioritic (TTG) gneisses with mafic and sedimentary enclaves, formed between 2.7 and 2.5 Ga and metamorphosed at amphibolite facies in the north to granulite faces in the south close to 2.4 Ga as mentioned in this paper.
Abstract: The Late Archean crust south of Krishnagiri, Tamil Nadu, consists of tonalitic-trondhjemitic-granodioritic (TTG) gneisses with mafic and sedimentary enclaves, formed between 2.7 and 2.5 Ga and metamorphosed at amphibolite facies in the north to granulite facies in the south close to 2.5 Ga. Migmatization occurred at all grades, and numerous small granite bodies were emplaced near the amphibolite-to-granulite facies horizon. This nearly syn-accretion meta-morphism affected the entire crust and left a chemically differentiated section later exposed by uplift and erosion. Detailed chemical and petrographic study of >60 samples across a 90 km traverse provides evidence for an essentially unbroken crustal cross-section: Paleopressures range from 4 kbar (corresponding to 12-14 km paleodepth) in the north to 8 kbar (corresponding to 24-28 km paleodepth) to the south. Corresponding paleotemperatures vary between 650° and 800°C across the section. Mineralogic grade monitors, particularly increasing $TiO_{2}$ conte...

93 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the temperature variation of the fractionation of oxygen in exchange reactions between dissolved carbonate and water and between calcite and water was calculated on theoretical grounds, and checked experimentally.
Abstract: The temperature variation of the fractionation of oxygen in exchange reactions between dissolved carbonate and water and between calcite and water and calculated on theoretical grounds, and checked experimentally. In the course of the experiments it was necessary to investigate several methods of decomposing calcium carbonate to carbon dioxide for mass spectrometer analysis. A method was developed for growing calcium carbonate from solution with the same isotopic composition as the carbonate shells of organisms produced at the same temperature from water of the same isotopic composition, and the results of these experiments at various temperatures are expressed in an equation relating the temperature of formation with the isotopic composition of the calcium carbonate and of the water.

3,579 citations


"Regional Carbonate Alteration of th..." refers methods in this paper

  • ...First the samples were reacted at 25°C for about 24 hrs, which liberated CO2 from the calcite component in the sample (McCrea 1950)....

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Journal ArticleDOI
TL;DR: In this paper, an empirically derived relationship between the chemical composition of a carbonate in the CaCO3-(Ca, Mg)(CO3)2-FeCO3 system and the function 103 In α at 100°C is 103 ∆ α = 8.94XCaCO3 + 9.29XMgCO3+ 8.77XFeCo3 where Xi is the mole percent of component i in the carbonate.

768 citations


"Regional Carbonate Alteration of th..." refers methods in this paper

  • ...…+5.9 Alkali gabbro (shonkinite) R405 +6.2 R258 +6.4 a [] omitted from mean. b 87Sr b 86. of sample at 800 Ma. fraction entirely from ankerite, and by using published values for Aco2-calcite and Aco2-ankerite at the appropriate temperatures (Friedman and O'Neil 1978; Rosenbaum and Sheppard 1986)....

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Journal ArticleDOI
TL;DR: In this article, carbon and oxygen isotopes and magnesium between coexisting dolomite and calcite have been determined for marbles and calcareous schists of a wide variety of metamorphic environments from Vermont and the Grenville Province of Ontario.
Abstract: Fractionations of carbon and oxygen isotopes and magnesium between coexisting dolomite and calcite have been determined for marbles and calcareous schists of a wide variety of metamorphic environments from Vermont and the Grenville Province of Ontario. Concordant equilibrium fractionations are given by 83% of the samples. Calibration of the isotopic thermometers using the Mg-calcite solvus thermometer gave in the temperature range: 650°>T°>100°C $$ \begin{gathered} 1,000\ln \alpha _{D - Ct}^{O^{18} } = 0.45 (10^6 T^{ - 2} ) - 0.40 \hfill \\ 1,000\ln \alpha _{D - Ct}^{O^{18} } = 0.18 (10^6 T^{ - 2} ) + 0.17. \hfill \\ \end{gathered} $$

453 citations


"Regional Carbonate Alteration of th..." refers background in this paper

  • ...The variation of Aquartz dolomite with temperature may be estimated from experimental and empirical determinations of the fractionation between the mineral pairs quartz-calcite and dolomite-calcite (Northrop and Clayton 1966; Sheppard and Schwarcz 1970; Matthews and Katz 1977; Clayton et al. 1989)....

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  • ...…N=17, mean= 1.8, (Jiang et al., 1988) T=450-620°C Aquartz- ankerite, Hamersley Range, (Becker & Clayton, 1976), N=26, mean =2.1 T ~ 300°0 C A quartz-dolomite, ~500°C Clayton et al., 1989; Sheppard & Schwarcz, 1970; Northrop & Clayton, 1966; Matthews & Katz, 1977. quartz-plagioclase Figure 6....

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  • ...Quartzankerite fractionations are similar to those predicted for quartz-dolomite at a temperature of ~500°C (Northrop and Clayton 1966; Sheppard and Schwarcz 1970; Matthews and Katz 1977; Clayton et al. 1989) and indicate significantly higher temperatures than the quartz-ankerite pairs from the…...

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Journal ArticleDOI
TL;DR: In this article, the carbonate-exchange technique was used to obtain diopside, forsterite, magnetite, and calcite isotope fractionations of the form 1000 ln α = A × 106T−2, where the coefficient A is given in the following table.

416 citations