TY - JOUR
T1 - Petrogenetic implications of mineral chemical data for the Permian Baima igneous complex, SW China
AU - Shellnutt, J. Gregory
AU - Pang, Kwan Nang
N1 - Funding Information:
The manuscript benefitted from constructive reviews by Marco Fiorentini and Marek Locmelis. We would like to thank Mei-Fu Zhou (HKU), Paul Robinson (Dalhousie University), Ma Yuxiao (CUST), Bor-Ming Jahn (NTU), Der-Chuen Lee (AS), Yoshi Iizuka (AS) and Zhao Hao (CUST) for their support. JSG would like to acknowledge the support of the National Science Council through grant 100-2116-M-003-006-MY2.
PY - 2012/9
Y1 - 2012/9
N2 - The Late Permian Fe-Ti oxide ore-bearing Baima igneous complex (BIC) is one of three gabbro-granitoid complexes with the Emeishan large igneous province. Mineral compositions are determined for the BIC layered gabbro in order to constrain subsolidus and magma chamber processes. The averaged compositions of cumulus olivine, clinopyroxene and plagioclase within individual samples range from Fo65-76, Mg# = 75 to 82 and An49-64 but they are not correlative. The observed mineral compositions are consistent with those modeled using the pHMELTS program. Highly variable magnetite compositions are consistent with extensive subsolidus re-equilibration and exsolution. The occurrence of reversely-zoned granular olivine in Fe-Ti oxide ores is a manifestation of Mg transfer between Fe-Ti oxides and olivine at relatively high (< 1150 °C) subsolidus temperatures. The primary oxide is inferred to be an aluminous titanomagnetite. Similar to other layered intrusions in the region, the gabbroic unit of the BIC displays Zr depletion which is consistent with loss of a residual liquid during magma differentiation. If the most Zr-rich syenites of the complex are taken into account, the Zr budgets between the combined gabbro-syenite and the basalts are similar. This indicates that the BIC most likely represents a closed system in terms of magma extraction.
AB - The Late Permian Fe-Ti oxide ore-bearing Baima igneous complex (BIC) is one of three gabbro-granitoid complexes with the Emeishan large igneous province. Mineral compositions are determined for the BIC layered gabbro in order to constrain subsolidus and magma chamber processes. The averaged compositions of cumulus olivine, clinopyroxene and plagioclase within individual samples range from Fo65-76, Mg# = 75 to 82 and An49-64 but they are not correlative. The observed mineral compositions are consistent with those modeled using the pHMELTS program. Highly variable magnetite compositions are consistent with extensive subsolidus re-equilibration and exsolution. The occurrence of reversely-zoned granular olivine in Fe-Ti oxide ores is a manifestation of Mg transfer between Fe-Ti oxides and olivine at relatively high (< 1150 °C) subsolidus temperatures. The primary oxide is inferred to be an aluminous titanomagnetite. Similar to other layered intrusions in the region, the gabbroic unit of the BIC displays Zr depletion which is consistent with loss of a residual liquid during magma differentiation. If the most Zr-rich syenites of the complex are taken into account, the Zr budgets between the combined gabbro-syenite and the basalts are similar. This indicates that the BIC most likely represents a closed system in terms of magma extraction.
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U2 - 10.1007/s00710-012-0217-7
DO - 10.1007/s00710-012-0217-7
M3 - Article
AN - SCOPUS:84865783209
SN - 0930-0708
VL - 106
SP - 75
EP - 88
JO - Mineralogy and Petrology
JF - Mineralogy and Petrology
IS - 1-2
ER -