Structural and economic characteristics of New England mica deposits

Cameron, Eugene N.; Larrabee, David Marcel; McNair, Andrew Hamilton; Page, J.J.; Shainin, V.E.; Stewart, Glenn W.

doi:10.2113/gsecongeo.40.6.369

Cited by 5 publications

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“…See, for example, the work of Smith and Page ( 1941), Olson . ( 1942), Bannerman ( 1943, Page, Hanley, and Heilirich (1943), Stewart (1944)~ J11hns and'Vright (1944), Olson, Pa~•kkr, and Page (1944), de Aln~eida, John~ton, Leo-nardos, and Scorza ( 1944), Olson ( 1944), Cameron, Larrabee, McNair, Page, Shainin, and Stewart (1945), Johnston ( 1945), andJahns ( 1946). It has been shown by careful studies in many areas that concentrations of economically desirable pegmatite minerals commonly occur in rock units quite distinct from adjacent barren units; hence recent work has fully confirmed the suggestions of many earlier investigators.…”

Section: Internal Structure Of the Pegmatitesmentioning

confidence: 99%

“…Many geologists have accepted most elements of the two-process theory and have applied it • to pegmatites in all parts of the world. The reports of Fraser ( 1930), Palache ( 1934), Hitchen ( 1935), Jenks ( 1935) , Switzer (1938), and Cameron, Larrabee, McNair, Page, Shainin, and Stewart ( 1945) deal with pegmatites in New England. Hess ( 1940) wrote on North Carolina and Pegau (1928;1929;1932, pp.…”

Section: Two-process Concept Of Pegmatite Originmentioning

confidence: 99%

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Mica deposits of the southeastern Piedmont, Part 1, General features

Jahns¹,

Griffitts²,

Heinrich³

1952

Professional Paper

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Pl\ge 1.'ABLE1. Summary data on the number of mica mines and prospects in the Piedmont region of the Southeastern States__ 2. General characteristics of pegmatites in the principal districts of the southeastern Piedmont___________________ 3. Occurrence of minerals in pegmatite areas of the southeastern Piedmont____________________________________ 4. Relative productivity of mica deposits by types___________________________________________ __ ____________ 5. Domestic and Indian size groups for clear sheet mica_____________________________ __ ________ ___ ___________ 6.

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Section: Internal Structure Of the Pegmatitesmentioning

confidence: 99%

Section: Two-process Concept Of Pegmatite Originmentioning

confidence: 99%

Mica deposits of the southeastern Piedmont, Part 1, General features

Jahns¹,

Griffitts²,

Heinrich³

1952

Professional Paper

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Alpha-decay damage in minerals of the pyrochlore group

1988

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Abstract. X-ray diffraction analysis and transmission electron microscopy have been used to study the effects of alpha-decay damage in pyrochlore group minerals, characterized by the general formula A1 ,~BzO6(O,OH,F)I -n'pH20.As defined by the XRD intensity ratio I/Io, both the saturation dose (for which I/Io =0.1-0.0) and the dose which signifies the initial loss of crystallinity (for which I/Io = 1.0-0.8) increase as a function of geologic age. The increase is attributed to annealing of isolated alpha-recoil tracks back to the original crystalline structure. The tracks have calculated mean lives, za, on the order of 108 years. In contrast, minerals which remain crystalline (e.g., uraninite, UO2) despite doses of up to 1018 alpha-events/mg have mean alpha-recoil track lives ~ 104 years (Eyal and Fleischer 1985).After correcting the calculated dose for annealing of alpha-recoil damage, I/Io is observed to decrease exponentially to zero over the dose range 0.02-1.0 x 1016 alphaevents/rag. The relationship between I/Io and "corrected" dose was used to calculate an average alpha-recoil track diameter of 4.6 nm, in which < 2600 atoms are displaced. XRD line broadening due to strain dominates the first half of the crystalline-to-metamict transition, reaching a maximum of 0.003, then decreasing to < 0.001. Line broadening due to decreasing crystallite size dominates the latter half of the transition. Estimated crystallite dimensions decrease from 450 nm to < 15 nm prior to reaching the fully metamict state. With increasing dose HRTEM images of microlites from the Harding pegmatite sequentially exhibit: 1) mottled diffraction contrast, 2) isolated 1-5 nm aperiodic areas, 3) coexisting aperiodic and crystalline areas, 4) relict" islands" of crystalline material in an aperiodic matrix, and 5) complete loss of lattice fringe periodicity. With no consideration given to alpha-recoil track fading, the transition covers a dose range of 0.04-1.7x 1017 alpha-events/mg. Using a value of za=108 years, this dose range is corrected down to 0.02-1.2 x 10 ~6 alpha-events/mg.The metamict state is characterized by a range of M-M and M-O distances which give rise to bands of diffuse scattering centered at 0.30 nm and 0.18 nm, respectively, in x-ray and electron diffraction patterns. Random image contrast shown by HRTEM is consistent with a random network type structure, an interpretation supported by EX-AFS/XANES studies (Greegor et al. 1985a(Greegor et al. , b, 1987. The structure of metamict pyrochlore consists of an aperiodic framework of corner-sharing B--O polyhedra. Compared to the crystalline precursor, the metamict state displays a reduced M-O coordination number and mean bond length, increased distortion of the B-site, and a slight increase in the average M-M distance.

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Branchville, Fairfield County, Connecticut

Marcin¹

1981

Rocks & Minerals

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Structural and economic characteristics of New England mica deposits

Cited by 5 publications

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Mica deposits of the southeastern Piedmont, Part 1, General features

Mica deposits of the southeastern Piedmont, Part 1, General features

Alpha-decay damage in minerals of the pyrochlore group

Branchville, Fairfield County, Connecticut

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