Applied Mineral Exploration
Discussion and research relevant to mineral
exploration. Mineral geochemistry of the Sangan skarn deposit, NE Iran: Implication for the evolution of hydrothermal fluid.
Fatemeh Sepidbar, Hassan Mirnejad, Jian-Wei Li,
Chunjing Wei, Luke L. George, Kingsley Burlinson.
Abstract
The Sangan iron skarn deposit is located in the
Sabzevar-Dorouneh Magmatic Belt of northeastern Iran. The skarn
contains zoned garnet, clinopyroxene and magnetite. Cores and rims
of zoned garnets are generally homogeneous, having a relatively
high REE, low LREE/ HREE ratios, and positive Eu anoma-lies. The
cores of the zoned clinopyroxenes are exceptionally HREE-rich,
with relatively high REE and HREE/LREE ratios, as well as positive
Eu anomalies. Clinopyroxene rims are LREE-rich, with rela-tively
low REE contents and HREE/LREE ratios, and do not have Eu
anomalies. Magnetite grains are enriched in LREEs in comparison
with the HREEs and lack Eu anomalies. Variations of fluid
composi-tion and physicochemical conditions rather than YAG-type
substitution mechanism are considered to have major control on
incorporating trace elements, including REE, into the skarn
mineral assemblage. Based on baro-acoustic decrepitation analysis,
the calc-silicate and magnetite dominant stages were formed at
similar temperatures, around 350–400 ◦ C. In the Sangan skarns,
hydrothermal fluids shifted from near-neutral pH, reduced
conditions with relatively high REE, low LREE/HREE ratios, and
U-rich characteristics towards acidic, oxidized conditions with
relatively low REE, high LREE/HREE ratios, and U-poor
characteristics.