Chapter 7. BUFFERING, INFILTRATION, and the CONTROL of INTENSIVE VARIABLES during METAMORPHISM

Rice, Jack M.; Ferry, John M.

doi:10.1515/9781501508172-011

Cited by 44 publications

(31 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The actual changes in fluid conditions could be evaluated considering the relative amount of solid reactants and products, based on modal analyses, combined with estimated fluid composition and known equilibrium constants of relevant reactions (Frost, 1979;Rice and Ferry, 1982). Such studies are in progress, but it may be anticipated that sulfidation of wall rocks will depress the total sulfur content of the fluid, decreasing the solubility of gold (Seward, 1973).…”

Section: Isochores For Type I and 2 Inclusions In Quartz-mentioning

confidence: 99%

The Fazenda Brasileiro gold deposit, Bahia; geology, hydrothermal alteration, and fluid inclusion studies

Teixeira¹,

Kishida²,

Marimon³

et al. 1990

Economic Geology

View full text Add to dashboard Cite

The high-grade gold mineralization at Fazenda Brasileiro occurs in quartz-albite-sulfide veins hosted by iron-rich metagabbros and forms the upper part of a differentiated mafic sill.The veins are enveloped by zones of hydrothermal alteration in which the metamorphic greenschist facies assemblage has been replaced by new mineral associations with a distinct zonation. Based on petrographic criteria these associations are classified into (1) parent rock, (2) zone of incipient alteration, (3) zone of advanced alteration, and (4) vein. The sequence of alteration is characterized by a major decrease in the chlorite content along with increases in albite, carbonates, pyrite, and arsenopyrite.Ore deposition resulted from the interaction between wall rocks and a low-salinity, H20-CO2-CH4-dominated hydrothermal fluid containing Na, S, and Au, which percolated through permeable zones developed during late-stage deformation. The deposit shows marked overall similarities with other greenschist facies gold deposits, such as Hunt, Sigma, and Kerr-Addison, in regard to the hydrothermal alteration pattern.

show abstract

Section: Isochores For Type I and 2 Inclusions In Quartz-mentioning

confidence: 99%

The Fazenda Brasileiro gold deposit, Bahia; geology, hydrothermal alteration, and fluid inclusion studies

Teixeira¹,

Kishida²,

Marimon³

et al. 1990

Economic Geology

View full text Add to dashboard Cite

show abstract

“…In particular, intrusion of magma into a metasedimentary sequence that includes carbonate and silicate minerals can lead to CO 2 -producing (decarbonation) metamorphic reactions, and to minor H 2 O-producing reactions when hydrous minerals are present. Because mineral reactions are directly related to compositional properties of hydrodynamic systems (Greenwood, 1975;Rice and Ferry, 1982;Ferry, 1991), metamorphic petrologists have had some success in deducing the general properties of fossil systems from studies of mineral assemblages (e.g., Moore and Kerrick, 1976;Bowman and Essene, 1982;Bucher-Nurminen, 1982;Hover-Granath et al, 1983;Labotka et al, 1988;Ferry et al, 2002;Nabelek, 2002). One goal is to deduce the temperature-fl uid composition-time (T-XCO 2 fl uid -t) paths of contact aureoles in order to determine how a hydrodynamic system evolves over its life span [XCO 2 fl uid is CO 2 /(CO 2 +H 2 O)].…”

Section: Introductionmentioning

confidence: 99%

Fluid evolution and kinetics of metamorphic reactions in calc-silicate contact aureoles—From H2O to CO2 and back

Nábělek

2007

Geol

View full text Add to dashboard Cite

Mineral assemblages in contact-metamorphic aureoles are the products of the interplay between heat transfer and fl uid fl ow induced by intrusion of magma. In wall rocks containing carbonate and silicate minerals, metamorphic reactions produce CO 2 , which then becomes part of the hydrodynamic system. Although observed assemblages are the ultimate products of T-XCO 2 fl uid -t paths in aureole rocks, the complexities of the paths, and hence the evolution of a hydrodynamic system, are diffi cult to decipher from them. Numerical simulations were conducted to model the mineralogical evolution in a hydrodynamic system and to evaluate the extent and effects of reaction retardation. Simulations reveal that fl uid composition in the inner aureole evolves rapidly toward high XCO 2 fl uid as the rocks heat up before an appreciable amount of water is exsolved out of the pluton. After local fl uid pressure drops when early reactions are coming to completion, infi ltration of magmatic water becomes signifi cant and can drive production of typical inner aureole minerals such as wollastonite. Fluid compositions in the outer aureole refl ect largely (1) the initial CO 2 production, as fl uids are driven down the pressure gradients from the inner aureole, and (2) the subsequent infi ltration of magmatic H 2 O. Simulations also suggest temperature overstepping of the onset of reactions and retarded consumption of reactant minerals, which leads to coeval metastable reactions. However, the fi nal simulated mineral assemblage in the inner aureole refl ects equilibration with H 2 O-rich fl uids that is usually seen in the fi eld, although evidence for kinetic retardation may be preserved in some rocks, especially in the outer aureole.

show abstract

“…The distribution of these isobarically univariant and invariant assemblages provides evidence of 'internal buffering' (Fig. 7) of fluids within the marbles (Rice & Ferry, 1982). Below the +sill isograd equilibrium fluid compositions constrained by these assemblages are at intermediate to low Xco,, and buffering paths are commonly controlled by the early exhaustion of quartz as a reactant phase.…”

Section: Siliceous Dolomitic Marblesmentioning

confidence: 95%

The nature and distribution of fluids during amphibolite facies metamorphism, Naxos (Greece)

Buick¹,

Holland²

1991

Journal Metamorphic Geology

View full text Add to dashboard Cite

On the basis of fluid inclusion evidence, pervasive influx of deep-seated C0,-rich fluids has been invoked to account for mid-to upper amphibolite facies (M2,) metamorphism on the island of Naxos (Cyclades, Greece). In this paper, mineral devolatilization and melt equilibria are used to constrain the composition of both syn-and post-peak-M2, fluids in the deepest exposed levels of the metamorphic complex. The results indicate that peak-M2, fluids were spatially and compositionally heterogeneous throughout the high-grade core of the complex, whereas post-peak-M2, fluids were generally water-rich. The observed heterogeneities in syn-M2, fluid composition are inconsistent with pervasive C0,-flushing models invoked by previous workers on the basis of fluid inclusion evidence. It is likely that few C0,-rich fluid inclusions on Naxos preserve fluids trapped under peak metamorphic conditions. It is suggested that many of these inclusions have behaved as chemically open systems during the intense deformation that accompanied the uplift of the metamorphic complex. A similar process may explain the occurrence of some C0,-rich fluid inclusions in granulite facies rocks.

show abstract

Chapter 7. BUFFERING, INFILTRATION, and the CONTROL of INTENSIVE VARIABLES during METAMORPHISM

Cited by 44 publications

References 0 publications

The Fazenda Brasileiro gold deposit, Bahia; geology, hydrothermal alteration, and fluid inclusion studies

The Fazenda Brasileiro gold deposit, Bahia; geology, hydrothermal alteration, and fluid inclusion studies

Fluid evolution and kinetics of metamorphic reactions in calc-silicate contact aureoles—From H2O to CO2 and back

The nature and distribution of fluids during amphibolite facies metamorphism, Naxos (Greece)

Contact Info

Product

Resources

About