Izvorni znanstveni članak

https://doi.org/10.4154/gc.2017.03

Alkali Metasomatism and Th-REE Mineralization in the Choghart deposit, Bafq district, Central Iran

Khalegh Khoshnoodi ; Department of Geology, Faculty of Earth Science, University of Shahid Beheshti, Tehran, Islamic Republic of Iran
Mehrdad Behzadi ; Department of Geology, Faculty of Earth Science, University of Shahid Beheshti, Tehran, Islamic Republic of Iran
Mohammad Gannadi-Maragheh ; Atomic Energy Organization of Iran, Nuclear Science and Technology Research Institute, Tehran, Islamic Republic of Iran
Mohammad Yazdi ; University of Shahid Beheshti, Faculty of Earth Science, Department of Geology, Tehran, Islamic Republic of Iran

Sažetak

The Choghart iron oxide-apatite (IOA) deposit is located 124 km southeast of Yazd, in the Bafq district within the Central Iranian microcontinent. The Choghart deposit is hosted by the rhyolitic rocks of the Early Cambrian volcano-sedimentary sequence (the Esfordi formation). Both host rocks and the orebodies are crosscut by diabase dykes. Tectonically, the Choghart rhyolites represent the continental margin setting and the Choghart diabase dykes formed in the back-arcbasin environment, respectively, indicating that the evolution of the Bafq district is associated with subduction of Palaeotethys oceanic crust beneath the Central Iranian microcontinent followed by formation of continental arc related granitoids and rhyolites and then formation of back-arc basin diabase dykes. Similar to the other subduction-related rhyolites, the Choghart rhyolite is enriched in Th and LREE compared to Ia, Nb, and HREE.

The main host minerals of Th and REE in the Th-REE mineralization zone are thorite and sphene. Albitization is the most important alteration aspect related to Th-REE mineralization (mainly Th, La, Ce, Nd, and Y). In addition to albite, Th-REE mineralization is associated with actinolite, augite, diopside, minor microcline and orthoclase, plus magnetite, calcite, pyrite, rutile, and minor amounts of chalcopyrite. The negative Eu anomaly in Th mineralization zone, as well as the paragenetic occurrence of magnetite, pyrite and chalcopyrite with thorite suggest that Th-REE mineralization formed in relatively reduced condition. The presence of paragenetic calcite accompanied by thorite and sphene in the Th-REE mineralization zone indicates that Th and REE were likely transported by the carbonate complexes in the mineralizing fluids. The similarity betweenthe chondrite-normalized REE patterns of the host rhyolite and the Th-REE mineralization zone suggests that post-magmatic driven fluids of continental margin rhyolitic magma played an important role in Th-REE mineralization.

Ključne riječi

Alkali Metasomatism; Th-REE Mineralization; breccia zone; Choghart deposit

Hrčak ID:

177954

URI

https://hrcak.srce.hr/177954

Datum izdavanja:

21.2.2017.

Posjeta: 1.850 *