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Role of sandstone provenance in the diagenetic albitization of feldspars A case study of the Jurassic Tera Group sandstones (Cameros Basin, NE Spain)

González Acebrón, Laura and Arribas Mocoroa, José and Mas, J.R. (2011) Role of sandstone provenance in the diagenetic albitization of feldspars A case study of the Jurassic Tera Group sandstones (Cameros Basin, NE Spain). Sedimentary Geology, 229 . pp. 53-63. ISSN 0037-0738

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Abstract

The Cameros Basin (Iberian Chain, NE Spain) formed during the latest Jurassic–Early Cretaceous rifting stage in an
extensional regime characterized by high subsidence rates. Its sedimentary infill (thicker than 6000 m) has been
subdivided into eight depositional sequences (DS) mainly composed of continental sediments. DS 1 and DS 2
represent the first rifting stage (Tera Group, Tithonian), mainly formed by fluvial and lacustrine sediments.
Sandstone petrofacies evolved from quartz-sedimentolithic in DS 1 to quartz-feldspathic in DS 2 due to the rifting
process. In DS 2, three different types of detrital feldspars (K-feldspars, albites and polysynthetic plagioclases) with
similar sodium-rich compositions (mean: Ab94.0 An4.5 Or1.5) can be recognized. Chemically pure nonluminescent
albites (AbN99%) are common. In DS 2, diagenetic albitization of both plagioclases and K-feldspars is inferred from
conventional microscopy observations, cathodoluminescence and electron microprobe analyses. DS 1 contains few
plagioclase grains, which showno evidence of transformation into albite.Although the albitization is characterized as
diagenetic it seems to be provenance-controlled since it affects the units showing higher original plagioclase/Kfeldspar
ratio (DS 2), due to the greater influence of plutonic and metamorphic source areas in DS 2. Possible Na
sources are: (1) the percolation ofmoderate to high salinity residual brines fromrelated alkaline lakes developed at
top of DS 2 in the eastern sector of the basin, (2) clay mineral reactions (sodium smectite to illite and chlorite)
indicated by mudstone composition in the interlayered mudstones, and (3) the replacement of detrital sodium
plagioclases by carbonate. These three sources can be complementary.


Item Type:Article
Uncontrolled Keywords:Albitization, K-feldspar, Plagioclase, Cathodoluminescence, Sandstone provenance
Subjects:Sciences > Geology > Petrology
ID Code:12758
Deposited On:20 May 2011 11:41
Last Modified:31 May 2011 08:20

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