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Diagenesis of Miocene pelitic sedimentary rocks in the Sava Depression (Croatia)

Anita Grizelj, D. Tibljas, M. Kovacic and D. Spanic
Diagenesis of Miocene pelitic sedimentary rocks in the Sava Depression (Croatia)
Clay Minerals (March 2011) 46 (1): 59-72


Miocene pelitic sedimentary rocks from six wells in the Sava Depression (sub-basin in the south-western part of the Pannonian Basin System) were investigated in order to determine the degrees of diagenetic alteration. Qualitative and semiquantitative mineral compositions of samples and the content of smectite in illite-smectite (I-S) were determined by X-ray powder diffraction (XRD). Vitrinite reflectance and thermal alteration index (TAI) were measured in order to estimate the palaeotemperatures. Carbonate minerals, clay minerals and quartz are the main constituents of the pelitic sediments. Feldspars (albite), pyrite, opal-CT and hematite are present as minor constituents in some rocks. The mineral composition of the rocks, apart from previously known differences caused by various depositional environments and clastic material provenance, is dependent on the degree of diagenetic processes. At elevated temperatures and large burial depths the minerals formed by alteration processes or precipitated at the surface; smectite, kaolinite and calcite were gradually replaced by minerals formed by diagenetic processes, i.e. by illite-smectite, illite, chlorite, Ca-excess dolomite/ankerite and albite. Based on XRD data for smectite, I-S and illite, three stages of diagenetic development have been established. The early stage was characteristic of samples at depths <1.8 km containing smectite, I-S of the random R0 type and detrital illite. The middle stage begins with the appearance of the ordered R1 type of I-S at the depths >1.8 km and temperature above 80 degrees C. At depths >4.6 km with corresponding temperatures >190 degrees C, the late stage began, characterized by the presence of R>1 I-S with <10% smectite.

ISSN: 0009-8558
EISSN: 1471-8030
Serial Title: Clay Minerals
Serial Volume: 46
Serial Issue: 1
Title: Diagenesis of Miocene pelitic sedimentary rocks in the Sava Depression (Croatia)
Affiliation: Croatian Geological Survey, Zagreb, Croatia
Pages: 59-72
Published: 201103
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 51
Accession Number: 2011-036763
Categories: Sedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
N44°30'00" - N44°30'00", E16°00'00" - E16°00'00"
Secondary Affiliation: University of Zagreb, HRV, CroatiaINA, HRV, Croatia
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201121
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