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Scientific Value of Coring the Proposed Southern Appalachian Research Drill Hole (1987) / Chapter Skim
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METAMORPHISM
Pages 24-27

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From page 24...
... Above all, research core drilling will provide a truly vertical section through a major metamorphic terrane that cannot be obtained from surface outcrops. METAMORPHIC ISOGRADS Metamorphic petrologists have traditionally deciphered the thermal structure of continental crust in orogenic belts by mapping isograds based on the appearance and disappearance of certain minerals produced by chemical reactions in rocks during metamorphism.
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From page 25...
... Correlation of isograds mapped at the surface with those established in core samples from the southern Appalachian site would provide points on isogradic surfaces over vertical distances approaching 6 to 8 km. This unprecedented increase in scale of observation could make possible pioneering investigations of the thermal structure of the crust before the main overthrust event, and investigations of heat sources and the controls of heat flow that ultimately determine the types of metamorphic rocks that are developed deep in the continental crust.
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From page 26...
... Specific metamorphic episodes probably can be correlated with major tectonic events that define the various orogenies, even in the complex polymetamorphic terranes of the southern Appalachians, through coordinated petrologic, microstructural, and geochronologic analysis of drill-core samples. HEAT AND MASS TRANSFER DURING METAMOSPHISM Petrologic studies of metamorphic rocks can provide information on the mechanism and patterns of heat and mass transfer during metamorphism.
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From page 27...
... Because of the fine grain size of cuttings from drilling of crystalline rocks and the variable response anticipated from different rock compositions, core is essential for research in metamorphic petrology at the southern Appalachian site. As anyone who has seen outcrops in metamorphic terranes can appreciate, rock type commonly changes on a centimeter scale.
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Key Terms

  • metamorphic rocks
  • southern appalachian
  • thermal structure
  • appalachian site
  • mass transfer

  • southern appalachians
  • thrust sheets
  • isogradic surfaces
  • thrust sheet
  • continental crust

  • heat flow
  • metamorphic reactions
  • paths determined
  • formational investigations
  • metamorphic episodes

  • developed deep
  • thrusting event
  • metamorphic petrologists
  • metamorphic terrane
  • surface outcrops

  • petrologic study
  • sheet model
  • individual samples
  • sheet thickness
  • geochronologic analysis

  • coordinated petrologic
  • sequential metamorphic
  • research core
  • rocks provides
  • major metamorphic


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