Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (10) Citing Articles via Google Scholar Google Scholar Articles by NIETO, F. Articles by PEACOR, D. R. Search for Related Content GeoRef GeoRef Citation

Retrograde diagenesis, a widespread process on a regional scale

¹ Instituto Andaluz de Ciencias de la Tierra and Departamento de Mineralogía y Petrología, University of Granada-CSIC, 18002 Granada, Spain, ² Departamento de Geología, University of Cádiz, Campus Río San Pedro, 11510 Puerto Real, Cádiz, Spain, ³ Departamento de Ciencias de la Tierra, University of Zaragoza, 50009 Zaragoza, Spain, ⁴ Dipartimento di Science della Terra, University of Siena, Siena, Italy, ⁵ Laboratory for Geochemical Research, Hungarian Academy of Sciences, H-1112 Budapest, Budaörsi út 45, Hungary, and ⁶ Department of Geological Sciences, The University of Michigan. Ann Arbor, MI-48109, US

^* E-mail: nieto{at}goliat.ugr.es

(Received 18 March 2004; revised 19 July 2004)

Pelitic and basic rocks occurring within prograde sequences in Portugal, Spain and Hungary have been studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The minerals formed in typical prograde reactions define the general sequences, but smectite, chlorite-smectite (corrensite) and/or berthierine were found to have replaced chlorite, whereas kaolinite and mixed-layer illite-smectite replaced illite-muscovite. Alteration occurred under conditions normally associated with diagenesis, subsequent to regional metamorphism, and we therefore refer to such processes with the term "retrograde diagenesis". In the cases studied and in other cited examples, reactions occurred on a regional basis via pervasive fluids under open-system conditions inferred to be related to tectonic stress. The observed alterations could generally not be inferred from XRD data, although the presence of pure smectite in sediments other than bentonite is suggestive of retrograde relations, especially where other minerals are consistent with a higher grade of diagenesis. Retrograde diagenesis is readily observed through imaging of textures by TEM, however. Textural features show that retrograde reactions are more common than generally assumed, and that care should be used in interpreting geological events where appropriate textural relations are not seen.

KEYWORDS: retrograde, diagenesis, XRD, TEM, SEM, illite-smectite, chlorite-smectite, regional metamorphism

This article has been cited by other articles:

				G. G. VOLDMAN, G. L. ALBANESI, and M. DO CAMPO Conodont palaeothermometry of contact metamorphism in Middle Ordovician rocks from the Precordillera of western Argentina Geological Magazine, July 1, 2008; 145(4): 449 - 462. [Abstract] [Full Text] [PDF]

				V. SUCHY, I. SYKOROVA, K. MELKA, J. FILIP, and V. MACHOVIC Illite 'crystallinity', maturation of organic matter and microstructural development associated with lowest-grade metamorphism of Neoproterozoic sediments in the Tepla-Barrandian unit, Czech Republic Clay Minerals, December 1, 2007; 42(4): 503 - 526. [Abstract] [Full Text] [PDF]

				S. BATTAGLIA, F. GHERARDI, G. GIANELLI, L. LEONI, and F. ORIGLIA Clay mineral reactions in an active geothermal area (Mt. Amiata, southern Tuscany, Italy) Clay Minerals, September 1, 2007; 42(3): 353 - 372. [Abstract] [Full Text] [PDF]

				M. VAZQUEZ, I. ABAD, J. JIMENEZ-MILLAN, F. T. ROCHA, P. E. FONSECA, and H. I. CHAMINE Prograde epizonal clay mineral assemblages and retrograde alteration in tectonic basins controlled by major strike-slip zones (W Iberian Variscan chain) Clay Minerals, March 1, 2007; 42(1): 109 - 128. [Abstract] [Full Text] [PDF]

				H. J. KISCH, R. SASSI, and F. P. SASSI The b0 lattice parameter and chemistry of phengites from HP/LT metapelites European Journal of Mineralogy, April 1, 2006; 18(2): 207 - 222. [Abstract] [Full Text] [PDF]

				S. HILLIER, M. J. WILSON, and R. J. MERRIMAN Clay mineralogy of the Old Red Sandstone and Devonian sedimentary rocks of Wales, Scotland and England Clay Minerals, March 1, 2006; 41(1): 433 - 471. [Abstract] [Full Text] [PDF]

				M. DO CAMPO and F. NIETO Origin of mixed-layered (R1) muscovite-chlorite in an anchizonal slate from Puncoviscana Formation (Salta Province, Argentina) Clay Minerals, September 1, 2005; 40(3): 317 - 332. [Abstract] [Full Text] [PDF]