,
Volume 18, Issue 3 (10-2010)
Abstract
The iron-apatite deposits of the Bafq mining district contain elevated REE content and occur together with vast alterations in country-rock which were formed due to widespread hydrothermal processes in Early Cambrian. Apatite and rare earth element geochemistry as well as radioactive isotope studies of Sm-Nd show that apatite formation might be due to hydrothermal activities and remobilization of coeval or older sedimentary phosphorites which are consequently deposited as apatite veins or veinlets associated with iron-oxide mineralization. This huge hydrothermal circulation was induced by intrusion of Early Cambrian igneous rocks such as granites and locally diorites, and is responsible to iron-apatite mineralization, locally associated with REE minerals, and extensive host rock alterations (sodic-potassic) due to vast fluid-rock interaction.
Somayeh Teimouri, Mansour Ghorbani, Soroush Modabberi,
Volume 30, Issue 4 (12-2022)
Abstract
The Iron-apatite deposits of Choghart and Chadormalu mining district are located in the western margin of the Bafq block and are hosted by Precambrian metamorphic basement complex, Late Precambrian sedimentary-volcanic units, and Late Precambrian-Early Cambrian plutonic rocks. The origin and relation of the rocks for a long time, which are known as metasomatites, have always been questioned. Based on petrography and mineral chemistry studies, five types of hydrothermal alterations have identified in these rocks. The oldest one is Na-alteration, which occurs at farther distances of iron deposits and is characterized by the presence of chessboard albite. The youngerst one is sodic-calcic alteration which is widespread and two-stages of the metasomatism model are characterized by the presence of tremolite-actinolite and is synchronous with the Fe-oxides. Potassic alteration occurs after two previous alteration phases, because of the influence of K-rich fluids and the formation of K-feldspar and secondary biotite. Silicate and sericite alteration has occurred as a late phase in the region.