Fisiografía y Geología
Facultad de Ciencias Exactas, Ingeniería y Agrimensura
Universidad Nacional de Rosario
Pellegrini 250, 2000 Rosario, Argentina
Boletín del Instituto de Fisiografía y Geología
Boletín del Instituto de Fisiografía y Geología, Volumen 83, 2003: 1-14.
Petrography and Geochemistry of the Early-Middle Devonian sandstones of the Padeha Formation in the North of Kerman, SE Iran. Implications for provenance
Hamed Zand-Moghadam, Reza Moussavi-Harami, Asadollah Mahboubi & Behnam Rahimi
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Hamed Zand-Moghadam [Zand1883@yahoo.com]
This study presents a petrological and geochemical characterization of the Early-Middle Devonian sandstones of the Padeha Formation in SE Central Iran, north of Kerman in order to determine the provenance on the basis of two measured stratigraphic sections. The sandstones are classified as quartzarenite and sublitharenite, and subordinately as litharenite based on framework composition. Modal analysis data from 55 samples of the Sarashk and Gazuieh sections revealed that the sandstones contain quartz, a few percent feldspars and lithic fragments (sedimentary and volcanic rocks). Most of the quartz grains are monocrystalline with straight to undulate extinction with a few polycrystalline grains. Petrographic studies indicate that the Padeha Formation sandstones may have been derived from plutonic and other recycled orogen rocks. Chemically, the major oxides of the sandstones from the Sarashk section are depleted with respect to the upper continental crust, except SiO2, which is related to the high maturity (presence of quartz) and the absence of Al-bearing minerals (phyllosilicates). The trace element concentrations (La, Th, Sc and Zr) and La/Sc (5.50-16.57), Th/Sc (1.12-4.14), La/Co (1.97-20.66), and Th/Co (0.72-4.75) of the Sarashk section indicate felsic source rocks for the sandstones. Furthermore, high Zr/Sc (48-368) and Th/U (0.5-6.8) values are typical for recycling. The chondrite-normalized rare earth element (REE) patterns support this interpretation. Light REE enrichment, negative Eu anomaly and flat heavy REE pattern are very similar to the old upper continental crust. Combined petrological-geochemical data and local Devonian palaeogeographical models show that the Padeha Formation sandstones mostly derived from felsic source rocks and mature recycled continental sedimentary rocks in the craton interior of Central Iran and adjacent areas and were deposited on the passive margin along the coastal setting of the Paleo-Tethys Ocean.
Key Words: Petrography, Geochemistry, Provenance, Sandstone, Padeha Formation, Kerman.