Low grade metamorphism of mafic rocks

A clustering of paleomagnetic poles for rock units of mid-Paleozoic (ca. 400 Ma) age in eastern New England indicates that a variety of lithologic types may be used to obtain virtual geomagnetic poles (VGP's) in an igneous–metamorphic terrain. These rock types include chilled margins of basaltic dikes or narrow dikes, hydrothermal alterations such as epidote veinlets, mafic rocks reset by low-grade metamorphism, and hypabyssal igneous bodies, particularly where there is evidence of hydrothermal activity.The results suggest the approach to be followed to obtain valid VGP's in similar geological belts in the Precambrian. The remanence directions in Devonian and Mississippian rock units in eastern Massachusetts and southern and northern Maine are close to other determinations of similar age within the Maritime block, demonstrating the potential usefulness of the procedures.

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Low-Grade Metamorphism of Mafic Rocks

10.1130/spe296 ◽

1995 ◽

Keyword(s):

Low Grade ◽

Mafic Rocks ◽

Grade Metamorphism

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Geochemistry and mineralogy of Rotliegend metavolcanic mafic rocks from Poland: pervasive low-grade metamorphism versus parent rock signature

Geological Society London Special Publications ◽

10.1144/gsl.sp.2004.223.01.17 ◽

2004 ◽

Vol 223 (1) ◽

pp. 393-413

Author(s):

Elżbieta Dubińska ◽

Paweł Bylina ◽

Bogusław Bagiński ◽

Grzegorz Kaproón ◽

Andrzej Kozłowski

Keyword(s):

Parent Rock ◽

Low Grade ◽

Mafic Rocks ◽

Grade Metamorphism

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DETRITAL MUSCOVITE FROM THE EDIACARAN-CAMBRIAN BOUNDARY ZONE IN ATLANTIC CANADA: AGE, PROVENANCE, AND EFFECTS OF LOW-GRADE METAMORPHISM ON 40AR/39AR SYSTEMATICS

10.1130/abs/2017ne-290567 ◽

2017 ◽

Cited By ~ 1

Author(s):

Sandra M. Barr ◽

◽

Willis E. Hames ◽

Chris E. White

Keyword(s):

Atlantic Canada ◽

Low Grade ◽

Boundary Zone ◽

Grade Metamorphism

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Low-grade metamorphism and accretion tectonics: Southern Uplands terrain, Scotland

Mineralogical Magazine ◽

10.1180/minmag.1985.049.352.04 ◽

1985 ◽

Vol 49 (352) ◽

pp. 335-344 ◽

Cited By ~ 49

Author(s):

A. E. S. Kemp ◽

G. H. J. Oliver ◽

J. R. Baldwin

Keyword(s):

Subduction Zones ◽

Structural Data ◽

Low Grade ◽

Structural Level ◽

Concomitant Increase ◽

Illite Crystallinity ◽

Grade Metamorphism ◽

Trench Slope ◽

Reflectance Data ◽

Trajectory Characteristic

AbstractPrevious studies of low-grade metamorphism in the Southern Uplands accretionary terrain indicated prehnite-pumpellyite facies/anchizone conditions developed throughout the area, except for local preservation of trench-slope sediments and an accreted seamount at zeolite facies/advanced diagenetic grade. New graptolite reflectance data are presented that show a general northward increase in temperature in the Southern Uplands. The results from two cross-strike traverses in the southern and central belts in contemporaneous sequences, using illite crystallinity, illite lateral spacing (bo) , and graptolite reflectance, indicate the development of systematic accretion-related low-grade metamorphism. Well-developed and constant anchizone conditions occur throughout the NE (Langholm) traverse, associated with common, F1 accretion-related folding and a regionally penetrative S1 cleavage. In the SW (Kirkcudbright) traverse, however, the youngest, last accreted packets are preserved at a transitional diagenetic stage and lack a penetrative S1 cleavage. Illite crystallinity, graptolite reflectance, and bo increase systematically northward through earlier accreted packets, reaching values of the NE traverse only at the northern end. The concomitant increase of bo with illite crystallinity suggests the relatively high P-low T trajectory characteristic of subduction zones. Integration of metamorphic and structural data relates increasing intensity of aceretion-related F1 folding, developmertt of S1 fabric, and onset of later fold phases to grade of metamorphism and structural level within the accretionary pile.

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