TITLE:
Dolomitization Mechanism Based on Petrography and Geochemistry in the Shotori Formation (Middle Triassic), Central Iran
AUTHORS:
A. Rahimi, M. H. Adabi, A. Aghanabati, M. R. Majidifard, A. M. Jamali
KEYWORDS:
Dolomitization, Petrography, Geochemistry, Shotori Formation, Central Iran
JOURNAL NAME:
Open Journal of Geology,
Vol.6 No.9,
September
26,
2016
ABSTRACT: Middle
Triassic carbonate sequences of Shotori Formation have a thickness of 70 m and
are deposited Robat-e-Kalmard region of Tabas city in Central Iran basin. Gradationally
and conformably overlying Sorkh shale Formation, Shotori Formation, mostly
composed of medium to thick dolomites (50 m), interbeded with thin lime and sandstones,
is disconformable by a laterite horizon at its upper boundary. This Formation mainly consists of fine-to-coarsely
crystalline dolomites. According to petrographic (fabric and grain size) and
geochemical (elemental analysis of Ca, Mg, Na, Sr, Fe, Mn) evidence, five
various types of dolomites were recognized in Shotori Formation. This variety
results from early and late diagenetic processes, triggering a change in dolomitizing
fluids and thereby forming various dolomites. Geochemical studies have revealed
that the dolomites of Shotori Formation have formed under meteoric diagenesis
and reducing conditions. Various dolomitization mechanisms are proposed for
various types of dolomites; that is
to say, Sabkha
model is considered for type 1 dolomite, mixing zone model for type 2 and 3 dolomites and burial model for type 4 and 5 dolomites.