Hostname: page-component-76fb5796d-25wd4 Total loading time: 0 Render date: 2024-04-25T18:55:38.564Z Has data issue: false hasContentIssue false
  • English
  • Français

Transmission electron microscopy study of very low-grade metamorphic evolution in Neoproterozoic pelites of the Puncoviscana formation (Cordillera Oriental, NW Argentina)

Published online by Cambridge University Press:  09 July 2018

M. Do Campo  and
F. Nieto
M. Do Campo*
Affiliation:
Instituto de Geocronología y Geología Isotópica and Facultad de Ciencias Exactas y Nautrales, U.B.A., Pabellón INGEIS, Ciudad Universitaria, 1428-Buenos Aires, Argentina
F. Nieto
Affiliation:
Departamento de Mineralogía y Petrología and I.A.C.T., Universidad de Granada-CSIC, Avda. Fuentenueva s/n, 18002-GranadaSpain
*
*E-mail: marga@ingeis.uba.ar
Get access Rights & Permissions [Opens in a new window]

Abstract

The Puncoviscana Formation, largely cropping out in NW Argentina, is mainly composed of a pelite-greywacke turbidite sequence affected by incipient regional metamorphism and polyphase deformation. Metapelites, composed mainly of quartz, albite, dioctahedral mica and chlorite, were sampled in the Lules-Puncoviscana and Choromoro belts. Lattice-fringe images, selected area electron diffraction and analytical electron microscopy analyses, coupled with previous data from white mica crystallinity index, indicate a state of reaction progress for Puncoviscana slates consistent with medium anchizone- to epizone-grade metamorphism. The 2M polytype prevails in dioctahedral micas, coexisting in a few cases with the 1Md polytype as a consequence of lack of equilibrium. The 2Mpolytype coexists with 3T in two slates and long-range four-layer and ten-layer stacking sequences were identified in another sample. Samples with 3T and long-range stacking sequences present b values characteristic of intermediate–high pressure metamorphism and ordered chlorites (1L, 2L, 3L and 7L) prevail.

Based on the Si contents of dioctahedral micas and considering peak temperatures of ∼350 –400ºC, pressures from 5 kbar and 5 –7 kbar were derived for metapelites from the Lules- Puncoviscana and Choromoro belts, respectively. These values agree with facies series derived from the b values. Micas with a wide range of phengitic substitution, as evidenced by Fe + Mg and Si contents, coexist. These variations could not arise from the disturbing effect of detrital white K-mica because TEM evidence indicates that they are absent or represent <10% of the mica population. Thus, compositional variations suggest that dioctahedral micas of individual slates crystallized at different pressure conditions in response to the P-T path of the metamorphism. Moreover, in several biotite-free slates the illite crystallinity (IC) values lead to an underestimation of the metamorphic grade attained in these rocks.

The coexistence of IC corresponding to anchizone and the occurrence of biotite in some slates and felsic metavolcanic rocks intercalated in the Puncoviscana metasediments are interpreted to be the result of a metamorphic path including a relatively high-pressure/ low-temperature (HP/LT) event, followed by a lower-pressure overprint possibly at higher temperatures than the HP/LTevent. Small micas formed during the high-pressure stage would prevail in the <2 mm fraction, producing anchizone IC.

Keywords

Central AndesPuncoviscana Formationintermediate Na-K dioctahedralmicaswonesitemixed layersillite crystallinity
Type
Research Article
Information
Clay Minerals , Volume 38 , Issue 4 , December 2003 , pp. 459 - 481
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2003

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Azañón, J.M. (1994) Metamorfismo de alta presión/baja temperatura, baja presión/alta temperatura y tectó-nica del Complejo Alpujárride (Cordilleras Bético – Rifeñas). PhD thesis, Universidad de Granada, Spain, 327 pp.Google Scholar
Azan˜ón, J.M. & Crespo-Blanc, A. (2000) Exhumation during a continental collision inferred from the tectonometamorphic evolution of the Alpujarride Complex in the central Betics (Alboran Domain, SE Spain). Tectonics, 19, 549– 565.Google Scholar
Bailey, S.W. (1982) Nomenclature for regular interstratifications. American Mineralogist, 67, 394 –398.Google Scholar
Banfield, J.F. & Murakami, T. (1998) Atomic-resolution transmission electron microscope evidence for the mechanism by which chlorite weathers to 1:1 semiregular chlorite-vermiculite. American Mineralogist, 83, 348– 357.CrossRefGoogle Scholar
Bucher, K. & Frey, M. (1994) Petrogenesis of Metamorphic Rocks. Springer-Verlag, Berlin.Google Scholar
Cliff, G. & Lorimer, G.W. (1975) The quantitative analysis of thin specimens. Journal of Microscopy, 103, 203–207.Google Scholar
Champness, P.E., Cliff, G. & Lorimer, G.W. (1981) Quantitative analytical electron microscopy. Bulletin de Minéralogie, 104, 236 –240.Google Scholar
Dalla-Torre, M., Livi, K., Veblen, D.R. & Frey, M. (1996) White K-mica evolution from phengite to muscovite in shales and shale matrix melange, Diablo Range, Californ ia. Contributions to Mineralogy and Petrology, 123, 390–405.Google Scholar
Do Campo, M. (1999a) Metamorfismo del basamento en la Cordillera Oriental y borde oriental de la Puna. Pp. 41–51 in: Relatorio XIV Congreso Geológico Argentino Geología del Noroeste Argentino (González Bonorino, G., Omarini, R. & Viramonte, J., editors). Universidad de Salta, Argentina.Google Scholar
Do Campo, M. (1999b) Mineralogía, geoquímica y geocronolog ía de la Formación Puncoviscana (Neoproterozoico) entre los 23º30’ y 25º50’ de Latitud Sur, Noroeste de Argentina. PhD thesis (unpublished), Buenos Aires University, Argentina.Google Scholar
Do Campo, M. & Cagnoni, M. (2001) The Rb-Sr isochron method applied to low-grade metamorphic rocks, the case of the Puncoviscana Formation, NW Argentina. III South American Symposium on Isotope Geology, Pucón, Actas, 26 – 29.Google Scholar
Do Campo, M., Nieto, F. & Omarini, R. (1998) Mineralogía de arcillas y metamorfismo de la Formación Puncoviscana en localidades de la Cordillera Oriental y Puna, Argentina. X Congreso Latinoamericano de Geología, Buenos Aires, Actas, 2, 217–223.Google Scholar
Do Campo, M., Nieto, F., Omarini, R. & Ostera, H. (1999) Neoproterozoic K-Ar ages for the metamorphism of the Puncovi scan a Formation , Northwestern Argentina. II South American Symposium on Isotope Geology, Carlos Paz, Actas, 48–53.Google Scholar
Dong, H. & Peacor, D.R. (1996) TEM observations of coherent stacking relations in smectite, I/S and illite of shales: Evidence for MacEwan crystallites and dominance of 2M1 polytypism. Clays and Clay Minerals, 44, 257 –275.Google Scholar
Franceschelli, M., Leoni, L. & Sartori, F. (1991) Crystallinity distribution and crystallinity-b 0 relationships in white K-micas of Verrucano metasediments (Northern Apennines, Italy). Schweizerische Mineralogische und Petrographische Mitteilungen, 71, 161 –167.Google Scholar
Franceschelli, M., Pandeli, E., Puxeddu, M., Porcu, R. & Fadda, S. (1994) Illite crystallinity in pelitic and marly rocks from the Northern Apennines (southern Tuscany and Umbria, Italy). Neues Jahrbuch für Mineralogie Monatshefte, 8, 367– 384.Google Scholar
Frey, M. (1969) A mixed-layer paragonite/ phengite of low grade metamorphic origin. Contributions to Mineralogy and Petrology, 24, 63–65.Google Scholar
Frey, M. (1978) Progressive low-grade metamorphism of a black shale formation, Central Swiss Alps, with special reference to pyrophyllite and margarite bearing assemblages. Journal of Petrology, 19, 95–135.Google Scholar
Giorgetti, G., Goffé, B., Memmi, I. & Nieto, F. (1998) Metamorphic evolution of Verrucano metasediments in northern Apennines: new petrological constraints. European Journal of Mineralogy, 10, 1295–1308.Google Scholar
Giorgetti, G., Memmi, I. & Peacor, D.R. (2000) Retarded illite crystallinity caused by stress-induced sub-grain boundaries in illite. Clay Minerals, 35, 693–708.Google Scholar
Guidotti, C.V. (1984) Micas in metamorphic rocks. Pp. 357–467 in. Micas (Bailey., S.W. editor). Reviews in Mineralogy, 13. Mineralogical Society of America, Washington, D.C.CrossRefGoogle Scholar
Guidotti, C.V., Mazzoli, C., Sassi, F.P. & Blencoe, J.G. (1992) Compositional controls on the cell dimensions of 2M1 muscovite and paragonite. European Journal of Mineralogy, 4, 283–297.Google Scholar
Guidotti, C.V., Sassi, F.P. & Blencoe, J.G. (1989) Compositional controls on the a and b cell dimensions of 2M1 muscovite. European Journal of Mineralogy, 1, 71–84.Google Scholar
Guidotti, C.V., Sassi, F.P., Blencoe, J.G. & Selverstone, J. (1994a) The paragonite –muscovite solvus: I. P-T-X limits derived from the Na –K compositions of natural, quasibinary paragonite – muscovite pairs. Geochimica et Cosmochimica Acta, 58, 2269–2275.Google Scholar
Guidotti, C.V., Yates, M.G., Dyar, M.D. & Taylor, M.E. (1994b) Petrogenetic implications of the Fe+3 content of muscovite in pelitic schists. American Mineralogist, 79, 793– 795.Google Scholar
Hongn, F.D., Acuña, P.A., Mon, R. & Kirschbaum, A.M. (2001a) Deformación paleozoica en el área de La Colorada. Sierra de Cobres (NO de la Argentina). X Congreso Argentino de Geología Económica, Salta, Actas, 1, 57–63.Google Scholar
Hongn, F.D., Tubía, J.M., Aranguren, A., Mon, R. & Battaglia, R. (2001b) Intrusión del granito rojo del batolito de Tastil en areniscas eopaleozoicas en el angosto de la Quesera, Cordillera Oriental, Salta. Revista de la Asociación Geológica Argentina, 56, 249–252.Google Scholar
Jezek, P. (1990) Análisis sedimentológico de la Formación Puncoviscana entre Tucumán y Salta. Pp. 9 –36 in. El Ciclo Pampeano en el Noroeste Argentino (F.G., Aceñolaza, H. Miller & A.J., Toselli. editors). Universidad Nacional de Tucumán, Tucumán, Argentina.Google Scholar
Jiang, W.T. & Peacor, D.R. (1993) Fomation and modification of metaestable intermediate sodium potassium mica, paragonite and muscovite in hydrothermally altered metabasites from North Wales. American Mineralogist, 78, 782–793.Google Scholar
Jullien, M., Baronnet, A. & Goffé B. (1996) Ordering of the stacking sequence in cookeite with increasing pressure. An HRTEM study. American Mineralogist, 81, 67–78.Google Scholar
Kilmurray, J.O., Merodio, J.C. & Rapela, C.W. (1974) Las metamorfitas cordier íticas del á rea Estación Incahuasi-Santa Rosa de Tastil, Provincia de Salta: Rasgos petrológicos y geoquímicos. Revista de la Asociación Geológica Argentina, 29, 425– 442.Google Scholar
Kisch, H.J. (1987) Correlation between indicators of very low-grade metamorphism. Pp. 227 –300 in. Lowtemperature Metamorphism (M. Frey, editor). Blackie, London.Google Scholar
Kretz, R. (1983) Symbols for rock-forming minerals. American Mineralogist, 68, 277–279.Google Scholar
Laird, J. (1988) Chlorites: metamorphic petrology. Pp. 405 –496 in. Hydrous Phyllosilicates (Bailey., S.W. editor). Reviews in Mineralogy, 19. Mineralogical Society of America, Washington, D.C.Google Scholar
Lee, J.H. & Peacor, D.R. (1985) Ordered 1:1 interestratification of illite and chlorite: a transmission and analytical electron microscopy study. Clays and Clay Minerals, 33, 463–467.Google Scholar
Lee, J.H., Peacor, D.R., Lewis, D.D. & Wintsch, R.P. (1984) Chlorite-illite/muscovite interlayered and interstra tified crystals: A TEM STEM study. Contributions to Mineralogy and Petrology, 88, 372–385.Google Scholar
Lee, J.H., Peacor, D.R., Lewis, D.D. & Wintsch, R.P. (1986) Evidence for syntectonic crystallization for the mudstone to slate transition at Lehigh Gap, Pennsylvania, U.S.A. Journal of Structural Geology, 8, 767–780.Google Scholar
Livi, K.J.T., Veblen, D.R., Ferry, J.M. & Frey, M. (1997) Evolution of 2:1 layered silicates in low-grade metamorphosed Liass ic shales of Central Switzerland. Journal of Metamorphic Geology, 15, 323–344.Google Scholar
López Munguira, A. & Nieto, F. (2000) Transmission electron microscopy study of very low-grade metamorphic rocks in Cambrian sandstones and shales, Ossa-Morena Zone, southwest Spain. Clays and Clay Minerals, 48, 213–223.Google Scholar
Massone, H.J. & Schreyer, W. (1987) Phengite geobarometry based on the limiting assemblage with K-feldspar, phlogopite and quartz. Contributions to Mineralogy and Petrology, 96, 212–224.Google Scholar
Merriman, R.J. & Peacor, D.R. (1999) Very low-grade metapelites: mineralogy microfabrics and measuring reaction progress. Pp. 10 –60 in. Low-grade Metamorphism (M., Frey & D., Robinson, editors). Blackwell Science, Oxford, UK.Google Scholar
Merriman, R.J. Roberts, B. & Peacor, D.R. (1990) A transmission electron microscope study of white mica crystallite size distribution in a mudstone to slate transitional sequence, North Wales, UK.Google Scholar
Contributions to Mineralogy and Petrology, 106, 27–40.Google Scholar
Mon, R. & Hongn, F.D. (1991) The structure of the Precambrian and Lower Paleozoic basement of the Central Andes between 22º and 32ºS Lat. Geologische Rundschau, 80, 745–758.Google Scholar
Mon, R. & Hongn, F.D. (1996) Estructura del basamento proterozoico y paleozoico inferior del norte argentino. Revista de la Asociación Geológica Argentina, 51, 3–14.Google Scholar
Nieto, F. & Sánchez-Navas, A. (1994) A comparative X.D. and T.M. study of the physical meaning of the white mica ‘crystallinity’ index. European Journal Google Scholar
of Mineralogy, 6, 611–621.Google Scholar
Nieto, F., Velilla, N., Peacor, D.R. & Ortega Huertas, M. (1994) Regional retrograde alteration of sub-greenschist facies chlorite to smectite. Contributions to Mineralogy and Petrology, 115, 243–252.Google Scholar
Nieto, F., Ortega-Huertas, M., Peacor, D.R. & Arostegui, J. (1996) Evolution of illite/smectite from early diagenesis through incipient metamorphism in sediments of the Basque-Cantabrian Basin. Clays and Clay Minerals, 44, 304–323.Google Scholar
Omarini, R.H. (1983) Caracterización litológica, diferenciaciónygénesis de la Formación Puncoviscana entre el Valle de Lerma y la Faja Eruptiva de la Puna. PhD thesis (unpublished). Salta University, Argentina, 202 pp.Google Scholar
Omarini, R. & Baldis, B.A.J. (1984) Sedimentología y mecanismos deposici onales de la Formación Puncovi scana (Grupo Lerma, Precámbric o- Cámbrico) del noroeste argentino. IX Congreso Geológico Argentino, Actas I: 384 – 398.Google Scholar
Omarini, R., Sureda, R.J., Götze, H.J., Seilacher, A. & Pflüger, F.P. (1999) Puncoviscana folded belt in the Northwestern Argenti na: testimony of Late Proterozoic Rodinia fragmentation and pre- Gondwana collisional episodes. Internati onal Journal of Earth Sciences, 88, 76–97.Google Scholar
Orozco, M., Alonso-Chaves, F.M. & Nieto, F. (1998) Development of large north-facing folds and their relation to crustal extension in the Alborán domain (Alpujarra s region, Betic Cordillera s, Spain). Tectonophysics, 298, 271– 295.Google Scholar
Peacor, D.R. (1992) Diagenesis and low-grade metamorphism of shales and slates. Pp. 335 –380 in. Minerals and Reactions at the Atomic Scale: Transmission Electron Microscopy (Buseck., P.R. editor). Reviews in Mineralogy, 27. Mineralogical Society of America, Washington, D.C.Google Scholar
Ramos, V.A. & Basei, M. (1997) Gondwanan, perigondwanan, and exotic terranes of southern South America. South-American Symposium on Isotope Geology, Actas, 250 –252.Google Scholar
Rieder, M., Cavazzini, G., D’yakonov, Y.S., Frank-Kamenetskii, V.A., Gottardi, G., Guggenheim, S., Komal, P.V., Müller, G., Neiva, A.M.R., Radoslovich, E.W., Robert, J.L., Sassi, F.P., Takeda, H., Weiss, Z. & Wones, D.R. (1998) Nomenclature of the micas. Clays and Clay Minerals, 46, 586–595.Google Scholar
Sassi, F.P., Guidotti, C.V., Rieder, M. & De Pieri, R. (1994) On the occurrence of metamorphic 2M1 phengites: some thoughts on polytypism and crystallization conditions of 3T phengites. European Journal of Mineralogy, 6, 151–160.Google Scholar
Schmidt, D. & Livi, K.J.T. (1999) HRTEM and SAED investigations of polytypism, stacking disorder, crystal growth, and vacancies in chlorites from subgreenschist facies outcrops. American Mineralogist, 84, 160–170.Google Scholar
Schmidt, D., Schmidt, S.T.., Mullis, J., Mahlmann, R.F. & Frey, M. (1997) Very low grade metamorphism of the Taveyanne formation of western Switzerland. Contributions to Mineralogy and Petrology, 129, 385– 403.Google Scholar
Shau, Y.H., Feather, M.E., Essene, E.J. & Peacor, D.R. (1991) Genesis and solvus relations of submicrosco-pically intergrown paragonite and phengite in a blueschist from northern California. Contributions to Mineralogy and Petrology, 106, 367–378.Google Scholar
Spear, F.S., Hazan, R.M. & Rumble, I.I.D. (1981) Wonesite: a new rock-forming silicate from the Post Pond Volcanics, Vermont. American Mineralogist, 66, 100–105.Google Scholar
Toselli, A.J. (1990) Metamorfismo del Ciclo Pampeano. Pp. 181–197 in. El Ciclo Pampeano en el Noroeste Argentino (Aceñolaza, F.G., Miller, H. & Toselli., A.J. editors). Universi dad Nacional de Tucumán, Tucumán, Argentina.Google Scholar
Toselli, A.J. & Rossi de Toselli, J.N. (1982) Metamorfismo de la Formación Puncoviscana en las provincias de Salta y Tucumán, Argentina. V Congreso Latinoamericano de Geología, Buenos Aires, Actas, 2, 37–52.Google Scholar
Turner, J.C.M. (1960) Estratigrafía de la Sierra de Santa Victoria y adyacencias. Boletín Academia Nacional de Ciencias de Cordoba, 41, 163–196.Google Scholar
Van der Pluijim, B.A., Lee, J.H. & Peacor, D.R. (1988) Analytical electron microscopy and the problem of potassium diffusion. Clays and Clay Minerals, 36, 498–504.Google Scholar
Veblen, D.R. (1983a) Exsolution and crystal chemistry of the sodium mic a wonesite. American Mineralogist, 68, 554– 565.Google Scholar
Veblen, D.R. (1983b) Microstructures and mixed layering in intergrown wonesite, chlorite, talc, biotite, and kaolinite. American Mineralogist, 68, 566–580.Google Scholar
Velde, B. (1965) Experimental determination of muscovite polymorph stabilities. American Mineralogist, 50, 436–449.Google Scholar
Warr, L.L. & Nieto, F. (1998) Crystalline size distributions in very low grade metamorphic pelites: a HRTEM and XRD study of clay mineral crystallinity index standards. Canadian Mineralogist, 36, 1453–1474.Google Scholar
Zhao, G., Peacor, D.R. and McDowell, D.S. (1999) Retrograde diagenesis of clay minerals in the Precambrian Freda sandstone, Wisconsin. Clays and Clay Minerals, 47, 119–130.Google Scholar