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Petrogenesis of Maobei rutile eclogites from the southern Sulu ultrahigh‐pressure metamorphic belt, eastern China
Author(s) -
ZHANG Z. M.,
LIOU J. G.,
ZHAO X. D.,
SHI C.
Publication year - 2006
Publication title -
journal of metamorphic geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.639
H-Index - 114
eISSN - 1525-1314
pISSN - 0263-4929
DOI - 10.1111/j.1525-1314.2006.00665.x
Subject(s) - eclogite , geology , geochemistry , metamorphic rock , plagioclase , rutile , basalt , omphacite , fractional crystallization (geology) , quartz , petrology , subduction , seismology , tectonics , paleontology
The Maobei complex in the southern Sulu ultrahigh‐pressure (UHP) metamorphic belt, eastern China, mainly consists of layered eclogites, garnet peridotites and orthogneisses. Based on the modal mineral and whole‐rock compositions, eclogites from the Maobei complex are divided into quartz eclogite, quartz‐rich eclogite, rutile eclogite, rutile‐rich eclogite and eclogite. The distinct spatial changes in the lithology and related chemical compositions indicate that this complex includes 10 rhythmic layers. The rutile eclogites have high TiO 2 (2.4–5.9 wt%), commonly coupled with high P 2 O 5 (up to 4.1 wt%) contents; most show fractionated REE patterns with slight positive Eu anomalies. The rutile‐rich eclogites have very high TiO 2 (3.3–5.7 wt%), FeO T (17.5–25.3 wt%), V (126–1163 ppm) and Co (14–132 ppm), and very low SiO 2 (38.0–42.3 wt%), Zr (24–85 ppm), Nb (0.3–6.9 ppm), Ta (<0.1–0.6 ppm) and total REE (10.7–334.0 ppm) contents, variable degree of LREE depletion, and positive Eu anomalies (Eu/Eu* = 1.1–2.9), and the Ti is decoupled from other high‐field‐strength elements. These characteristics are consistent with Fe‐Ti gabbros of typical layered intrusions, implying a cumulate of plagioclase, clinopyroxene and abundant accessory magnetite in an evolved basaltic magmatic chamber. Based on a normal stratigraphic sequence, the Maobei complex shows an iron‐enrichment trend, followed by alkaline enrichment with increasing fractionated crystallization and stratigraphic height. These facts, together with SHRIMP U‐Pb zircon ages of 773.7 ± 8.0 Ma, indicate that the protolith of the Maobei complex is a Neoproterozoic layered intrusion consisting of a base of peridogabbro, a main body of gabbro and minor granodiorite. Unusually high Ti, V and P contents in three rutile eclogite layers suggest that they are potential economic ore deposits.