Application of Oxygen and Carbon Isotopes in Separation ofLow and High Temperature Dolomites in Northeast of Iran

this study is focused on do lomi te s of the Chehel-Kaman Formation (Upper Paleocene) that is located in NE Iran. Field and petrographic studies lead to distinguish dl and d2 dolomites. dL is fine crystals (Ie.<;ser than 10 micron) and is associated with t:vaporatic sed ime nts. and d2 in addition to fint: crystals. contains coarser crystals (50-RO micron) without evaporatic sediments. Also. oxygen isotope of ell is hCltvicr than -2.5 %" PDB and oxygen isotope of d2 is lighter than - 6.5 %0 PDB. Cchr('39')lrbon isotope in these dolomites ranges between + 1.8 %0 to +3.5 %0 PDB. These data along with CL o bse rvation show that d l dolomites are formed in lower temperature (calculated temperature is 26°C) within supratidal environment, while d2 dolomites are formed in higher temperature (calculated temperature is more than n °C) during burial stage.