International Geologiical Congress - Oslo 2008

Home

Search Abstracts

Author Index

Symposia Programmes

Sponsors

Help

 

 

MRD-13 Ore deposits associated with black shales: from their origin to their environmental impacts

 

Markasheh sediment-hosted stratiform Cu mineralization in the Ravar region, Central Iran

 

Amir Mahdavi, Tarbiat Modares University (Islamic Republic of Iran)
Ebrahim Rastad, Tarbiat Modares University (Islamic Republic of Iran)
Mahbubeh Hosseini Barzi, Beheshti University (Islamic Republic of Iran)
 

 

In Central Iran, continental red bed sediments of Jurassic-Cretaceous age (Garadu red beds) extend over a very large area from Ravar to Tabas (more than 180 km). The greatest number of mineral occurrences in this area is Cu red bed-type mineralization, such as the Chahkuro and Geloshur occurrences in the north, the Markasheh deposit in northwestern Ravar, and the Garadu deposit in the Tabas area. Stratigraphically, the Ravar region from bottom to top includes: red sandstone and shale with micro-conglomerate to conglomerate (Garadu red beds; 300-500 m in thickness) that are overlain by upper Jurassic evaporate units, calcareous shale, gypsiferous marl and gypsum (25-30 m) and well to thick-bedded grey limestone (60-70 m). The Garadu red beds consist of alternating layers of oxidized red and reduced light grey sandstone. Copper mineralization in the Markasheh deposit occurs as four different reduced ore horizons in which cupriferous sulphides, occurring in several stratiform lens- like bodies (with 300-400 m in length and 0.2-6 m in thickness). Reducing environment resulted from presence of high amounts of plant fossil clasts and disseminated pyrite. Sulphids (principally chalcocite, bornite, covellite as well as minor amounts of chalcopyrite and pyrite) are hosted by coarse-grained sandstone micro-conglomerate and plant fossil bearing sandstones. The Cu mineralization occurs as chalcocite together with pyrite and covellite near red to grey boundaries within the strata. Copper, primarily as chalcocite replaced woody organic debris and disseminated pyrite in sandstone rocks. The location of mineralization is controlled by sedimentary facies and concentration of organic matter. Based on stratigraphic, petrographic, and mineralogical studies, it appears that Cu mineralization in the Ravar region is the first recognition of red bed-type sediment-hosted copper deposit in Jurassic-Cretaceous sequences in Iran. Keywords: Markasheh, Ravar, Redbed type, Cu deposit

 

CD-ROM Produced by X-CD Technologies