Writers : Mahboubi, A.; Moussavi Harami, R.; Nadjafi, M.; Yahya Sheibani, V.
Refference : The 21st Symposium on Geoscience;Tehran
Publishing Year : 1381

Abstract :
There are some scattered outcropes of limestones south of Mashhad along the Binalood Mountains and most of them are observable north of Aman_Abad village.
These deposites are mainly composed of limestones with a few horizons of siliciclastic, including sandstones and conglomerates.
The studies showed that the carbonate rocks where deposited in a shallow carbonate platform of ramp type, including open marine, shoal, lagoon and beach/tidal flat subenvironments. Petrographic studies also showed that diagenetic processes, which are acted up, on the Cretaceous carbonates, consist of compaction, cementation, micritization, replacement (silicification), and neomorphism. These processes are operated in diagenetic environments such as marine phreatic, meteoric phreatic, burial and uplift.
Geochemical data showed that the amount of oxygen isotopes in the limestone range between _11.191 to _2.145 PDB and the amount of carbon isotopes between 0.218 to 4.328 PDB.
This variation reveals a meteoric diagenetic environment. Decreasing trend in the value of oxygen isotopes with increasing the amount of Fe and Mn as well as decreasing Na, Sr also indicated that these rocks may have been exposed to the meteoric diagenetic environment too.
The calculated temperature for the ambient water, that calcite was deposited, is about 26ْC.
Subject List : Carbonatite Rocks, depositional history , diagenetic