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Title: Electrical conductivity and carbon in metamorphic rocks of the Yukon-Tanana Terrane, Alaska

Abstract

Electrical conductivity of a water-saturated quartz-mica-garnet-schist, collected from a surface outcrop near the Denali Fault Zone in the Yukon-Tanana terrane of east central Alaska, increases slightly with pressure to about 200 MPa. This behavior is unlike that exhibited by other Yukon-Tanana samples or by most rocks from other locations. Detailed petrographic examination of the sample revealed the presence of a stringer of carbonaceous material generally less than 10 {mu}m thick enclosed in and intergrown with one of the muscovite layers and extending for about 2 cm along the foliation. The stringer is probably responsible for the anomalous conductivity change with pressure, making the sample the first for which anomalous electrical conductivity behavior can be attributed to carbon associated with a specific feature. The carbonaceous stringer together with its host muscovite layer are deformed and broken around a rotated garnet porphyroclast. The authors interpret the textural relations to indicate that the carbonaceous material was formed by fluid deposition in a fracture formed within the muscovite layer, possibly during the main phase of metamorphism and deformation, and that the mica and carbon stringer were then deformed by the noncoaxial deformation responsible for rotation of the garnet porphyroclasts. Brittle deformation on the microscopicmore » scale is observed to have broken the connectivity of the carbon stringer, explaining in part why the rock does not exhibit anomalously high conductivity at 0.1 MPa (1 atm) pressure. The brittle deformation is interpreted to have been caused by unloading due to uplift. The observations indicate that carbonaceous material may exert a primary control on crustal electrical conductivity because it may be present as interconnected arrays in grain boundaries or microfractures or in megascopic, throughgoing fractures. 42 refs., 9 figs., 1 tab.« less

Authors:
; ;  [1]
  1. American Museum of Natural History, New York, NY (United States); and others
Publication Date:
OSTI Identifier:
245147
Resource Type:
Journal Article
Journal Name:
Journal of Geophysical Research
Additional Journal Information:
Journal Volume: 100; Journal Issue: B6; Other Information: PBD: 10 Jun 1995
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; METAMORPHIC ROCKS; ELECTRIC CONDUCTIVITY; YUKON TERRITORY; CARBON ADDITIONS; PRESSURE DEPENDENCE

Citation Formats

Mathez, E A, Peach, C L, and Leger, A. Electrical conductivity and carbon in metamorphic rocks of the Yukon-Tanana Terrane, Alaska. United States: N. p., 1995. Web. doi:10.1029/95JB00615.
Mathez, E A, Peach, C L, & Leger, A. Electrical conductivity and carbon in metamorphic rocks of the Yukon-Tanana Terrane, Alaska. United States. doi:10.1029/95JB00615.
Mathez, E A, Peach, C L, and Leger, A. Sat . "Electrical conductivity and carbon in metamorphic rocks of the Yukon-Tanana Terrane, Alaska". United States. doi:10.1029/95JB00615.
@article{osti_245147,
title = {Electrical conductivity and carbon in metamorphic rocks of the Yukon-Tanana Terrane, Alaska},
author = {Mathez, E A and Peach, C L and Leger, A},
abstractNote = {Electrical conductivity of a water-saturated quartz-mica-garnet-schist, collected from a surface outcrop near the Denali Fault Zone in the Yukon-Tanana terrane of east central Alaska, increases slightly with pressure to about 200 MPa. This behavior is unlike that exhibited by other Yukon-Tanana samples or by most rocks from other locations. Detailed petrographic examination of the sample revealed the presence of a stringer of carbonaceous material generally less than 10 {mu}m thick enclosed in and intergrown with one of the muscovite layers and extending for about 2 cm along the foliation. The stringer is probably responsible for the anomalous conductivity change with pressure, making the sample the first for which anomalous electrical conductivity behavior can be attributed to carbon associated with a specific feature. The carbonaceous stringer together with its host muscovite layer are deformed and broken around a rotated garnet porphyroclast. The authors interpret the textural relations to indicate that the carbonaceous material was formed by fluid deposition in a fracture formed within the muscovite layer, possibly during the main phase of metamorphism and deformation, and that the mica and carbon stringer were then deformed by the noncoaxial deformation responsible for rotation of the garnet porphyroclasts. Brittle deformation on the microscopic scale is observed to have broken the connectivity of the carbon stringer, explaining in part why the rock does not exhibit anomalously high conductivity at 0.1 MPa (1 atm) pressure. The brittle deformation is interpreted to have been caused by unloading due to uplift. The observations indicate that carbonaceous material may exert a primary control on crustal electrical conductivity because it may be present as interconnected arrays in grain boundaries or microfractures or in megascopic, throughgoing fractures. 42 refs., 9 figs., 1 tab.},
doi = {10.1029/95JB00615},
journal = {Journal of Geophysical Research},
number = B6,
volume = 100,
place = {United States},
year = {1995},
month = {6}
}