TY - JOUR
T1 - The Oligocene Avaj volcanic – plutonic complex of Central Iran
T2 - A record of magma evolution and mineral equilibria
AU - Babazadeh, Shahrouz
AU - Ghalamghash, Jalil
AU - Furman, Tanya
AU - D'Antonio, Massimo
AU - Raeisi, Davood
N1 - Funding Information:
This work has been partly financially supported by ?Iran National Science Foundation? (INSF; No. 97007604) grant to SB, and under the joint research program of Pennsylvania State University and Dipartimento di Scienze della Terra, dell'Ambiente e delle Risorse, University Federico II of Naples. SB is grateful to the Geological Survey of Iran for their assistance in obtaining EMP analyses and mosaic images for CSD. We collectively express our gratitude to two anonymous reviewers whose comments have greatly strengthened the paper, and to Ibrahim Uysal for his patient assistance throughout the editorial process.
Funding Information:
This work has been partly financially supported by “Iran National Science Foundation” (INSF; No. 97007604) grant to SB, and under the joint research program of Pennsylvania State University and Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, University Federico II of Naples. SB is grateful to the Geological Survey of Iran for their assistance in obtaining EMP analyses and mosaic images for CSD. We collectively express our gratitude to two anonymous reviewers whose comments have greatly strengthened the paper, and to Ibrahim Uysal for his patient assistance throughout the editorial process.
Publisher Copyright:
© 2021
PY - 2021/12
Y1 - 2021/12
N2 - The Avaj Oligocene volcanic – plutonic complex is part of extensive Cenozoic magmatic activity within the Urumieh-Dokhtar magmatic arc of Iran. We use whole rock geochemistry, mineral compositions and crystal size distributions (CSD) in a suite of co-genetic basalt, basaltic andesite and gabbro to determine their petrogenesis. Ca-rich cores in plagioclase (An79-86) overlap empirically modelled compositions, indicating equilibrium crystallization from melts represented by the whole-rock compositions. Clinopyroxene compositions (Mg# 74–80) are compatible with mildly fractionated mantle-derived magmas in an arc setting. Mineral-melt equilibrium is inferred from high Al contents and close correspondence between the measured DiHd and predicted KdFe–Mg (0.23–0.32) in clinopyroxenes, and Kd(Plg/melt)(An–Ab) values of plagioclase cores (0.11–0.15). Clinopyroxene-melt thermometers indicate crystallization at 1119–1173 °C for volcanic and 1099–1134 °C for plutonic rocks. Plagioclase crystal core saturation temperatures range from 1088–1162 °C (volcanic) and 1121–1163 °C (plutonic); these values overlap calculated mineral-melt equilibrium temperatures. Plagioclase CSDs are nearly straight for both volcanic and plutonic samples, with higher nucleation density and steeper slopes for the plutonic samples. Major element variations suggest the Avaj rocks represent co-genetic magmas related by fractional crystallization of the observed mineral phases. We suggest minor crustal assimilation occurred during ascent from a deeper reservoir to a shallower one; CSD data indicate longer magma residence time for plagioclase in the plutonic samples (∼117 years) compared to the residence time of basaltic samples (∼13 years).
AB - The Avaj Oligocene volcanic – plutonic complex is part of extensive Cenozoic magmatic activity within the Urumieh-Dokhtar magmatic arc of Iran. We use whole rock geochemistry, mineral compositions and crystal size distributions (CSD) in a suite of co-genetic basalt, basaltic andesite and gabbro to determine their petrogenesis. Ca-rich cores in plagioclase (An79-86) overlap empirically modelled compositions, indicating equilibrium crystallization from melts represented by the whole-rock compositions. Clinopyroxene compositions (Mg# 74–80) are compatible with mildly fractionated mantle-derived magmas in an arc setting. Mineral-melt equilibrium is inferred from high Al contents and close correspondence between the measured DiHd and predicted KdFe–Mg (0.23–0.32) in clinopyroxenes, and Kd(Plg/melt)(An–Ab) values of plagioclase cores (0.11–0.15). Clinopyroxene-melt thermometers indicate crystallization at 1119–1173 °C for volcanic and 1099–1134 °C for plutonic rocks. Plagioclase crystal core saturation temperatures range from 1088–1162 °C (volcanic) and 1121–1163 °C (plutonic); these values overlap calculated mineral-melt equilibrium temperatures. Plagioclase CSDs are nearly straight for both volcanic and plutonic samples, with higher nucleation density and steeper slopes for the plutonic samples. Major element variations suggest the Avaj rocks represent co-genetic magmas related by fractional crystallization of the observed mineral phases. We suggest minor crustal assimilation occurred during ascent from a deeper reservoir to a shallower one; CSD data indicate longer magma residence time for plagioclase in the plutonic samples (∼117 years) compared to the residence time of basaltic samples (∼13 years).
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U2 - 10.1016/j.jseaes.2021.104962
DO - 10.1016/j.jseaes.2021.104962
M3 - Article
AN - SCOPUS:85117388384
VL - 222
JO - Journal of Asian Earth Sciences
JF - Journal of Asian Earth Sciences
SN - 1367-9120
M1 - 104962
ER -