Clinopyroxenite from the Sulu ultrahigh-pressure terrane, eastern China: Origin and evolution of garnet exsolution in clinopyroxene
-
Ru Y. Zhang
und
Juhn G. Liou
Abstract
The Rizhao garnet clinopyroxenite occurs as small mantle slices faulted into subducted continental crust in the Sulu ultrahigh-pressure (UHP) terrane, China. Two representative garnet clinopyroxenites with exsolution microstructures were studied: (1) a massive ilmenite-rich specimen, composed of coarse-grained clinopyroxene containing abundant exsolution rods of grossularrich garnet (>20 vol%) + ilmenite (~3-4 vol%) in a fine-grained matrix of clinopyroxene + garnet + ilmenite; and (2) megacrystic garnet-bearing sample, characterized by garnet containing inclusions of clinopyroxene and ilmenite; the clinopyroxene inclusions show exsolution rods and blebs with variable amounts of garnet (1-15 vol%) and minor ilmenite. Both exsolved and matrix garnets have similar grossular-rich compositions. The aggregate composition of clinopyroxene + garnet + ilmenite intergrowth is similar to the whole-rock composition. We propose that the parental phase of exsolved garnet + ilmenite lamellae and clinopyroxene host was either a homogeneous clinopyroxene (hypothesis A) or a majoritic garnet (hypothesis B) that experienced three discrete evolution stages. If the parental phase was clinopyroxene (ABO3), with an Si deficiency in the B site, the Rizhao garnet clinopyroxenite could have an initial assemblage clinopyroxene ± Grt ± Ilm formed at nearsolidus conditions (≤ 1400 °C, at 5 GPa) in the upper mantle. The second stage is defined by garnet exsolution from the primary clinopyroxene involving decreasing temperature and/or increasing pressure, related to continental subduction. Coexisting clinopyroxene host and garnet exsolution (Grtexs) recrystallized at temperatures of ~900 °C at an assumed minimum P of 5 GPa. The third stage is represented by recrystallization of exsolution phases to form the fine-grained matrix of Cpx + Grt + Ilm at 700 °C and ≥ 3 GPa during the early exhumation of the UHP terrane. The speculative hypothesis B implies that the proposed majoritic garnet was from the mantle transition zone (<450 km depth); this suggestion remains to be tested.
© 2015 by Walter de Gruyter Berlin/Boston
Artikel in diesem Heft
- Structural systematics of hydrous ringwoodite and water in earth’s interior
- Compressibility of phase Egg AlSiO3OH: Equation of state and role of water at high pressure
- Synchrotron infrared spectroscopy of OH-chondrodite and OH-clinohumite at high pressure
- Structural deformation mechanisms of zeolites under pressure
- Variation of hydrogen bonded O···O distances in goethite at high pressure
- Pressure-controlled polytypism in hydrous layered materials
- OH– in synthetic and natural coesite
- Pressure-induced phase transformation of kalicinite (KHCO3) at 2.8 GPa and local structural changes around hydrogen atoms
- Potential docking sites and positions of hydrogen in high-pressure silicates
- Contrasting bonding behavior of two hydroxyl-bearing metamorphic minerals under pressure: Clinozoisite and topaz
- Experimental investigation of crystallization kinetics in a haplogranite system
- Assessment of cation substitutions along the gallium and fluorine analogue of the tremolite-glaucophane join
- Experimental hydrothermal alteration of partially metamict zircon
- On the origin of size-dependent and size-independent crystal growth: Influence of advection and diffusion
- Ordering in spinels—A Monte Carlo study
- Single-crystal in situ high-temperature structural investigation of the I1̅ –I2/c phase transition in Ca0.2Sr0.8Al2Si2O8 feldspar
- New clinopyroxene-liquid thermobarometers for mafic, evolved, and volatile-bearing lava compositions, with applications to lavas from Tibet and the Snake River Plain, Idaho
- Fe and Ni impurities in synthetic diamond
- Phase transformations and reaction kinetics during the temperature-induced oxidation of natural olivine
- Thermal infrared spectroscopy and modeling of experimentally shocked plagioclase feldspars
- Oxygen isotopic composition of nano-scale uraninite at the Oklo-Okélobondo natural fission reactors, Gabon
- Clinopyroxenite from the Sulu ultrahigh-pressure terrane, eastern China: Origin and evolution of garnet exsolution in clinopyroxene
- Letters. An assessment of nuclear microprobe analyses of B in silicate minerals
- Incommensurate phase in the kosmochlor-diopside join: A new polymorph of clinopyroxene
- Elastic properties of hydrous ringwoodite
- Thermochemistry of guest-free melanophlogite
- A simple model for the pressure preservation index of inclusions in diamond
Artikel in diesem Heft
- Structural systematics of hydrous ringwoodite and water in earth’s interior
- Compressibility of phase Egg AlSiO3OH: Equation of state and role of water at high pressure
- Synchrotron infrared spectroscopy of OH-chondrodite and OH-clinohumite at high pressure
- Structural deformation mechanisms of zeolites under pressure
- Variation of hydrogen bonded O···O distances in goethite at high pressure
- Pressure-controlled polytypism in hydrous layered materials
- OH– in synthetic and natural coesite
- Pressure-induced phase transformation of kalicinite (KHCO3) at 2.8 GPa and local structural changes around hydrogen atoms
- Potential docking sites and positions of hydrogen in high-pressure silicates
- Contrasting bonding behavior of two hydroxyl-bearing metamorphic minerals under pressure: Clinozoisite and topaz
- Experimental investigation of crystallization kinetics in a haplogranite system
- Assessment of cation substitutions along the gallium and fluorine analogue of the tremolite-glaucophane join
- Experimental hydrothermal alteration of partially metamict zircon
- On the origin of size-dependent and size-independent crystal growth: Influence of advection and diffusion
- Ordering in spinels—A Monte Carlo study
- Single-crystal in situ high-temperature structural investigation of the I1̅ –I2/c phase transition in Ca0.2Sr0.8Al2Si2O8 feldspar
- New clinopyroxene-liquid thermobarometers for mafic, evolved, and volatile-bearing lava compositions, with applications to lavas from Tibet and the Snake River Plain, Idaho
- Fe and Ni impurities in synthetic diamond
- Phase transformations and reaction kinetics during the temperature-induced oxidation of natural olivine
- Thermal infrared spectroscopy and modeling of experimentally shocked plagioclase feldspars
- Oxygen isotopic composition of nano-scale uraninite at the Oklo-Okélobondo natural fission reactors, Gabon
- Clinopyroxenite from the Sulu ultrahigh-pressure terrane, eastern China: Origin and evolution of garnet exsolution in clinopyroxene
- Letters. An assessment of nuclear microprobe analyses of B in silicate minerals
- Incommensurate phase in the kosmochlor-diopside join: A new polymorph of clinopyroxene
- Elastic properties of hydrous ringwoodite
- Thermochemistry of guest-free melanophlogite
- A simple model for the pressure preservation index of inclusions in diamond
