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Compositional Variation and Mineral Chemistry of the Jinshajiang and Lancangjiang Serpentinites, Yunnan Province, SW China
Author(s) -
MASOUD Ahmed E.I.,
YANG Jingsui,
LIU Fei
Publication year - 2014
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.12339
Subject(s) - peridotite , ophiolite , partial melting , geochemistry , pyroxene , geology , olivine , ultramafic rock , spinel , mantle (geology) , mineralogy , paleontology , tectonics
We present the whole rock and the mineral chemical data for upper mantle peridotites from the San‐Jiang region in Yunnan, SW China. These peridotites are a part of a Paleo‐Tethyan ophiolite belt occurring along the Jinshajiang and Lancangjiang suture zones. All samples of the Jinshajiang and Lancangjiang ultramafic rocks are completely serpentinized. The Jinshajiang serpentinites are characterized by no relict of olivine and pyroxene, and the Cr # content of spinels is 0.32–0.49. The Lancangjiang serpentinites were collected from two different locations; the northern location which has some relict of Opx (Al 2 O 3 is 0.13–2.2 wt%, TiO 2 is 0.004–0.057 wt% and Mg # content is 0.895–0.933) and the Cr # content of spinel is 0.26–0.55; the southern location, which has some relict of Olivine (Fo = 90–92.5 and NiO = 0.12–0.26 wt%), and spinel Cr # ranging from 0.41 to 0.57. The whole rock geochemical and the mineral chemistry data imply that the Jinshajiang and Lancangjiang serpentinites represent abyssal peridotites residues after ∼15–20% partial melting for the Jinshajiang and Lancangjiang serpentinites (south location), and ∼11–19% partial melting for the Lancangjiang serpentinites (north location). In addition, the compositional trends of the spinel analyses of the Lancangjiang serpentinites imply that the MORB melt‐peridotite interaction process played a significant role during their evolution. These processes are evidenced by an increase in Cr # with an increase in TiO 2 , whereas the spinel analyses of the Jinshajiang serpentinites display an increase in Cr # with a decrease in TiO 2 , indicating that the Jinshajiang serpentinites were subjected to a simple partial melting process.