Authors
J Gregory Shellnutt, Kuo-Lung Wang, Georg F Zellmer, Yoshiyuki Iizuka, Bor-Ming Jahn, Kwan-Nang Pang, Liang Qi, Mei-Fu Zhou
Publication date
2011/11/1
Journal
American Journal of Science
Volume
311
Issue
9
Pages
773-812
Publisher
American Journal of Science
Description
The Permian (∼260 Ma) Emeishan large igneous province of SW China contains three nearly identical gabbro-granitoid complexes that host giant Fe-Ti oxide deposits. The Fe-Ti oxide deposits are within the lower portions of evolved layered gabbroic intrusions and are spatially and temporally associated with A-type granitic plutons. The 264 ± 3 Ma Taihe layered gabbroic intrusion hosts a large magmatic Fe-Ti oxide deposit and is coeval with the Taihe peralkaline, A-type granitic pluton, which is dated at 261 ± 2 Ma. Within the A-type granitic pluton are microgranular enclaves, which have compositions intermediate between the gabbro and host granite. Primitive mantle-normalized incompatible element plots show corresponding reciprocal patterns between the mafic and felsic rocks. The chondrite-normalized REE patterns show Eu-anomalies changing from positive (Eu/Eu\* = 1.5 to 5.9) in the gabbroic intrusion to negative in the enclaves (Eu/Eu\* = 0.4 to 0.6) and granites (Eu/Eu\* = 0.2 to 0.5). Whole rock εNd~(T)~ values of the gabbroic intrusion (εNd~(T)~ = +2.5 to +3.3) are similar to those of the enclaves (εNd~(T)~ = +1.0 to 2.0) and granite (εNd~(T)~ = +1.5 to +1.9) whereas the zircon εHf~(T)~ values of the gabbro (εHf~(T)~ = +8.1 ± 0.8) are indistinguishable from those of the granites (εHf~(T)~ = +9.2 ± 1.0), suggesting that the parent magmas for all rock types originated from the same mantle source. Geochemical modeling indicates that the gabbros and granites can be generated by fractional crystallization of a common parental magma similar to high-Ti Emeishan flood basalt. The compositional jump from the gabbro to the enclaves is …
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