Abstract
Samples of a garnet granulite from the mafic border units of the Lake Chatuge, Georgia alpine peridotite body were found to contain lamellar intergrowths of a pargastic amphibole in augite having the typical appearance of an exsolution feature. Single crystal X-ray diffraction, optical, electron microprobe and conventional and analytical electron microscopic studies have provided data limiting the compositions and structures of the coexisting phases. Individual lamellae of both materials are from 0.5 to 2.0 μm in width with the lamellar interface parallel to {0 1 0}. The formulae of the minerals, as determined by a combination of electron microprobe and analytical electron microscopy, are (Na0.1Ca1.0Mg0.6Fe3+ 0.3)(Si1.8Al0.2)O6 for the pyroxene and Na0.7Ca1.9(Mg2.1Fe2+ 1.4Fe3+ 0.5Ti0.1Cr0.1Al0.8)(Si5.9Al2.1) O22(OH)2 for the amphibole. Several other studies have described intergrowths similar to those observed in this work, in general favoring exsolution as the formation mechanism for the intergrowths. In the Lake Chatuge samples however, replacement of pyroxene by amphibole is in part indicated by continuous gradation of amphibole lamellae into amphiboles rimming the clinopyroxenes.
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Blake DF, Allard LF, Peacor DR, Bigelow WC (1980) “Ultra-clean” X-ray spectra in the JEOL JEM-100CX. Proc 38th Ann Mtg Electron Microsc Soc Am, pp 136–137
Cliff G, Lorimer GW (1972) The quantitative analysis of thin metal foils using EMMA-4 — the ratio technique, Proc 5th Eur Congr Electron Microsc. Inst Physics, London, pp 140–141
Chliff G, Lorimer GW (1975) The quantitative analysis of thin specimens. J Microsc 103:203–207
Dallmeyer RD (1974) Eclogite inclusions in an alpine peridotite sill, Georgia-North Carolina: their chemistry and petrogenetic evolution. Am J Sci 274:356–377
Desnoyers C (1975) Exsolution d'amphibole, de grenat et de spinelle dans les pyroxènes de roches ultrabasiques: péridotite et pyroxénolites. Bull Soc Fr Mineral Crystallogr 98:65–77
Goldstein JJ, Costley JL, Lorimer GW, Reed SJB (1977) Quantitative X-ray analysis in the electron microscope. Proc Workshop Analyt Electron Microsc 1. Chicago, SEM, pp 315–323
Hartley ME III (1973) Ultramafic and related rocks in the vicinity of Lake Chatuge. Ga Dept Nat Res Bull 85:1–61
Lorimer GW, Champness PE (1973) Combined electron microscopy and analysis of an orthopyroxene. Am Mineral 58:243–248
Lorimer GW, Cliff G, Clark JN (1976) Determination of the thickness and spatial resolution for the quantitative analysis of thin foils. In: Developments in Electron Microscopy and Analysis. Proc Electron Microsc Analyt Group 75. Academic, Bristol London, pp 153–156
Nakajima Y, Hafner SS (1980) Exsolution in augite from the Skaergaard intrusion. Contrib Mineral Petrol 72:101–110
Nakajima Y, Ribbe PH (1980) Alteration of pyroxenes from Hokkaido, Japan to amphiboles, clays, and other biopyriboles. Neues Jahrb Mineral 6:258–268
Papike JJ, Ross M, Clark JR (1969) Crystal chemical characterization of amphiboles based on five new structure determinations. Mineral Soc Am, Spec Pap 2:117–136
Rucklidge JC, Gasparrini EL (1969) Specifications of a complete program for processing electron microprobe data: EMPADR VII. Dept Geol, Univ Toronto
Smith PPK (1977) An electron microscopic study of amphibole lamellae in augite. Contrib Mineral Petrol 59:317–322
Veblen DR, Buseck PR (1977) Petrologic implications of hydrous biopyriboles intergrown with igneous pyroxene. Trans Am Geophys Union (EOS) 58:1242
Veblen DR, Busek PR (1980) Microstructures and reaction mechanisms in biopyriboles. Am Mineral 65:599–623
Ymaguchi Y, Akai J, Tomity K (1978) Clinoamphibole lamellae in diopside of garnet lherzolite from Alpe Arami, Bellinzona, Switzerland. Contrib Mineral Petrol 66:263–270
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Contribution No. 368 from the Mineralogical Laboratory, Department of Geological Sciences, The University of Michigan, Ann Arbor, Michigan
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Isaacs, A.M., Brown, P.E., Valley, J.W. et al. An analytical electron microscopic study of a pyroxene-amphibole intergrowth. Contr. Mineral. and Petrol. 77, 115–120 (1981). https://doi.org/10.1007/BF00636515
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DOI: https://doi.org/10.1007/BF00636515