Volume 22, Issue No. 2, 1997

GENESIS AND ERUPTIVE ENVIRONMENT OF BASALTS _FROM THE GOGHER OPHIOLITIC MELANGE, _SOUTHWEST OF KERMAN, IRAN

M. Arvin* and E. Shokri*

*Department of Geology, College of Sciences, Kerman University, P.O. Box 133, 76135 Kerman, Iran.

Keywords: ophiolitic melange, petrology, tholeiite, transitional tholeiite. Central Iran.

ABSTRACT

The Late Cretaceous Gogher ophiolitic melange complex southwest of Kerman is part of the Mesozoic ophiolitic belt that surrounds the Central Iranian microcontinent. The melange consists of various blocks of ophiolite, lithology in a matrix composed chiefly of serpentinized and tectonized harzburgite. Despite the severe deformation many internal contacts are undisturbed and the original igneous contacts are preserved. Geochemical studies, particularly of the immobile elements, confirmed the presence of two distinct compositional groups in the mafic lavas: (a) transitional tholeiite basalts and (b) tholeiitic basalts. The overall trace and REE patterns are believed to reflect a relatively similar mantle source for the two lava groups. The Zr/Nb ratio together with trace element discrimination diagrams and MORB-normalized trace patterns show that the Gogher basalts are similar to those of island arc and transitional type MORB. The presence of serpentinite melange similar to those of many modern fracture zones, together with mafic dykes cutting the serpentinized peridotite in the Gogher ophiolitic melange, favour a ridge-transform setting for its origin. The ridge transform model suggests formation of the ophiolite in a narrow ocean basin separating the Sanandaj-Sirjan microcontinent from the Central Iran block in Late Cretaceous.