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- Title
Petrogenesis and Metallogenesis of the Mazaertag Layered Intrusion in the Tarim Large Igneous Province, NW China.
- Authors
CAO, Jun; WANG, Qimeng
- Abstract
The Mazaertag layered intrusion is located in the northwestern part of the Tarim large igneous province where several early Permian layered mafic-ultramafic intrusions host important Fe-Ti oxide deposits. The intrusion covers an area of ∼0.13 km2 and has a vertical stratigraphic thickness of at least 300 m. It consists chiefly of olivine clinopyroxenite, and is cut through by the nearby mafic-ultramafic dykes. In this paper, we report new mineral chemistry data and whole-rock chemical and isotopic compositions for the Mazaertag intrusion along with whole-rock isotopic compositions for the nearby mafic dykes. The averaged compositions of cumulus olivine, clinopyroxene and intercumulus plagioclase within individual samples range from Fo71-73, Mg# = 76 to 79 and An65-75 but they do not define sustained reversals. The observed mineral compositions are consistent with the differentiation of a single batch of magma in a closed system. Rocks of the Mazaertag intrusion are characterized by enrichment in light REE relative to heavy REE, positive Nb and Ta anomalies and a small range of age-corrected ∊Nd( t) (−0.1 to +0.9) and initial 87Sr/86Sr values (0.7044 to 0.7068). The slightly lower ∊Nd( t), initial 206Pb/204Pb and higher initial 87Sr/86Sr values of the intrusion compared to those of the least contaminated dykes [ ∊Nd( t) = +2.8 to +3.4; (206Pb/204Pb), = 18.516-18.521; (87Sr/86Sr)1 = 0.7038-0.7041] imply that the Mazaertag magma was subjected to small to modest degrees of contamination by the upper crust. The Sr-Nd isotopic compositions of the least contaminated dykes are consistent with derivation from a FOZO-like mantle source. The parental magma of the Mazaertag intrusion, estimated from clinopyroxene compositions using mineral-melt partition coefficients, has trace element compositions similar to some of the most primitive mafic dykes in the same area. This suggests that the Mazaertag intrusion and mafic dykes shared a similar mantle source. Therefore, the parental magma of the Mazaertag intrusion was interpreted to have originated from a mantle plume. Based on the Cr2O3 contents in titanomagnetite and less-evolved characteristics of the Mazaertag intrusion compared to the Wajilitag Fe-Ti oxide deposit in Bachu, it is speculated that there might not be a potential to find economic Fe-Ti oxide mineralization in the intrusion.
- Subjects
PYROXENE; FERRIC oxide; MAGMAS; EARTH'S mantle; MINERALIZATION
- Publication
Acta Geologica Sinica (English Edition), 2017, Vol 91, Issue 5, p1653
- ISSN
1000-9515
- Publication type
Article
- DOI
10.1111/1755-6724.13404