Anion Composition of Apatite in the Au-Cu Epithermal Deposit of Palai-Islica (Almería, SE Spain) as an Indicator of Hydrothermal Alteration

Abstract

The Palai-Islica deposit (Almería, SE Spain) is an Au-Cu epithermal deposit hosted in Neogene calc-alkaline andesites and dacites from the Cabo de Gata-Cartagena volcanic belt in the Betic Cordillera. Major element compositions of apatite from Palai-Islica orebody and related hydrothermally altered and unaltered volcanic rock from the region hosting the deposit were obtained to clarify the processes involved in their formation. Apatite in the host volcanic rocks is rich in chlorapatite and hydroxylapatite components (50–57% and 24–36%) and poor in fluorapatite components (12–21%), indicating assimilation processes of cortical Cl-rich material in the magmatic evolution. Apatite in the orebody sometimes has corrosion textures and is mostly fluorapatite (94–100%). Apatite from the hydrothermally altered host rock of the orebody systematically bears signs of corrosion and has variable and intermediate fluorapatite (19–100%), chlorapatite (1–50%), and hydroxylapatite (0–47%) components. The style of zonation and the composition are related to the proximity to the orebody. These features can be interpreted as the result of hydrothermal modification of high Cl, OH-rich volcanic apatites into F-rich apatites. The enrichment of F is related to the intensity of hydrothermal alteration and could therefore constitute a geochemical index of alteration and of mineralization processes.

Volatile (F, Cl, OH) concentrations in lunar apatites and britholites as a measure of lunar magmatic volatile abundances

“…This paper used them to determine magma ascension rates in this volcano. Carrillo-Rosúa et al, (2021) show how metasomatism has affected the anion composition of apatite grains in a gold-and silver-bearing ore body. Li et al (2020Li et al ( , 2021 have used volatile partitioning and diffusion to track magma ascension rates and the effusivity of eruptions in Merapi Volcano in Indonesia.…”