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Title: Porosity evolution, contact metamorphism, and fluid flow in the host basalts of the Skaergaard magma-hydrothermal system

Abstract

Temporal and spatial variations in porosity during contact metamorphism of the basaltic country rocks to the Skaergaard intrusion in East Greenland resulted in a complex hydrological evolution of the metamorphic aureole. Contrasts in macroscopic porosities in different lithologies led to differences in mineralogical, bulk chemical, and oxygen isotopic alteration, and units with greater macroscopic porosities record larger fluid flux during metamorphism. Calculated Darcy velocities indicate that the horizontal component of fluid flow in the aureole was toward the intrusive contact. In the actinolite + chlorite zone time-integrated fluid flux was higher in aa units ({approximately} 300 kg cm{sup {minus}2}) than in massive units ({approximately} 130 kg cm{sup {minus}2}). Approximately equal time-integrated fluxes of respectively 4 and 5 kg cm{sup {minus}2} in aa and massive units in the pyroxene zone indicate that the volume of fluid flow in the higher grade rocks was independent of primary porosity. These results are consistent with inward fluid migration in the actinolite + chlorite zone through an open network of pores whose abundance varied as a function of primary lava morphology. At higher metamorphic grades fluid fluxes were lower and were independent of primary porosity, probably as a consequence of (1) channelization of fluids duemore » to more extensive pore filling and (2) decreasing horizontal component of flow due to upward migration of fluids near the contact. The results of this study indicate that explicit provision for rock porosity aids interpretation of the nature of fluid flow during contact metamorphism in magma-hydrothermal systems.« less

Authors:
Publication Date:
Research Org.:
Stanford Univ., CA (United States)
OSTI Identifier:
5430297
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Thesis (Ph.D.)
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; 58 GEOSCIENCES; BASALT; HYDROTHERMAL ALTERATION; POROSITY; GREENLAND; HYDROTHERMAL SYSTEMS; CHLORITE MINERALS; FLUID FLOW; GEOTHERMAL FLUIDS; METAMORPHISM; MINERALOGY; PYROXENES; ROCK-FLUID INTERACTIONS; FLUIDS; GEOTHERMAL SYSTEMS; IGNEOUS ROCKS; MINERALS; OXYGEN COMPOUNDS; ROCKS; SILICATE MINERALS; SILICATES; SILICON COMPOUNDS; VOLCANIC ROCKS; 152003* - Geothermal Data & Theory- Rock-Water-Gas Interactions; 580000 - Geosciences

Citation Formats

Manning, C E. Porosity evolution, contact metamorphism, and fluid flow in the host basalts of the Skaergaard magma-hydrothermal system. United States: N. p., 1989. Web.
Manning, C E. Porosity evolution, contact metamorphism, and fluid flow in the host basalts of the Skaergaard magma-hydrothermal system. United States.
Manning, C E. Sun . "Porosity evolution, contact metamorphism, and fluid flow in the host basalts of the Skaergaard magma-hydrothermal system". United States.
@article{osti_5430297,
title = {Porosity evolution, contact metamorphism, and fluid flow in the host basalts of the Skaergaard magma-hydrothermal system},
author = {Manning, C E},
abstractNote = {Temporal and spatial variations in porosity during contact metamorphism of the basaltic country rocks to the Skaergaard intrusion in East Greenland resulted in a complex hydrological evolution of the metamorphic aureole. Contrasts in macroscopic porosities in different lithologies led to differences in mineralogical, bulk chemical, and oxygen isotopic alteration, and units with greater macroscopic porosities record larger fluid flux during metamorphism. Calculated Darcy velocities indicate that the horizontal component of fluid flow in the aureole was toward the intrusive contact. In the actinolite + chlorite zone time-integrated fluid flux was higher in aa units ({approximately} 300 kg cm{sup {minus}2}) than in massive units ({approximately} 130 kg cm{sup {minus}2}). Approximately equal time-integrated fluxes of respectively 4 and 5 kg cm{sup {minus}2} in aa and massive units in the pyroxene zone indicate that the volume of fluid flow in the higher grade rocks was independent of primary porosity. These results are consistent with inward fluid migration in the actinolite + chlorite zone through an open network of pores whose abundance varied as a function of primary lava morphology. At higher metamorphic grades fluid fluxes were lower and were independent of primary porosity, probably as a consequence of (1) channelization of fluids due to more extensive pore filling and (2) decreasing horizontal component of flow due to upward migration of fluids near the contact. The results of this study indicate that explicit provision for rock porosity aids interpretation of the nature of fluid flow during contact metamorphism in magma-hydrothermal systems.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1989},
month = {1}
}

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