Geochemical Behavior of Rare Earth Elements in Garnets of Khut Skarn Using Laser Ablation ICP-MS Data, W Yazd, Iran

Zahedi1, A; Boomeri, M; Mackizadeh, M.A

doi:10.22071/gsj.2015.42942

Geochemical Behavior of Rare Earth Elements in Garnets of Khut Skarn Using Laser Ablation ICP-MS Data, W Yazd, Iran

Document Type : Original Research Paper

Authors

A Zahedi1 ¹

M Boomeri ²

M.A Mackizadeh ³

¹ Ph.D., Department of Geology,Faculty of Sciences, Sistan & Baluchestan University, Zahedan, Iran

² Associate Professor, Department of Geology, Faculty of Sciences, Sistan & Baluchestan University, Zahedan, Iran

³ Assistant Professor, Department of Geology, Faculty of Sciences, Isfahan University, Isfahan, Iran

10.22071/gsj.2015.42942

Abstract

The garnets from the KhutSkarn in the west of Yazd have been formed as a result of hydrothermal activity ofOligo-Miocene calc-alkaline plutons. The chemical composition of garnets in the Khutskarn are divided into two solid solution of grossularitic-andraditic and almost pure andradite different types. The Fe-rich garnets are isotropic (Adr>96), whereasgrossularitic-andraditic garnets are anisotropic and show compositional zoning and sectorial twinning(Ad_74.3Gr_24.8-Ad_32.1Gr_66.6). The compositional zoning of anisotropic garnets may result from hydrothermal overgrowths on contact metamorphic minerals, variations in P, T, XCO₂, concentrations of Fe³⁺ and Al, or kinetic factors. The Laser Ablation ICP-MS results show isotropic garnets exhibit LREE-enriched and HREE-depleted patterns, with a positive Eu anomaly. These garnets grow rapidly under relatively high W/R ratios from the magmatic-derived fluids during infiltration metasomatism process, whereas anisotropic garnets have much lower enrichment in LREE and show a weak negative Eu anomaly. These garnets formed by prolonged interaction of pore fluids with the host rocks during the diffusive metasomatism process.

Keywords

Garnet

REE Geochemistry

Metasomatism

Skarn

Khut