Abstract
The Middle Paleozoic Maksyutov Complex is an important component of the Eurasian collisional orogeny. It consists of dominant mica-rich garnet schist and mica-poor quartzofeldspathic gneiss enclosing minor mafic eclogite boudins (unit no. 1). Employing Raman spectroscopy, we identified three cuboidal microdiamond inclusions (~2-3 micrometers in diameter) in garnet hosts from two different mica-poor gneissic samples. Broad spectral bands and high magnification SEM images suggest that the cuboids are fine-grained nanocrystalline diamond aggregates characterized by limited long-range ordering. Their poor crystallinity is compatible with relatively low-temperature, solid-state growth in the absence of both melt and a C-O-H-N fluid. Poor crystallinity, and small grain size suggest that such aggregates may represent the lowest temperature microdiamonds yet identified in nature. Their formation required ultrahigh-pressures (UHP) at a minimum of 3.2 GPa, and a metamorphic temperature of ~650 °C. Blocky graphite up to 10+ mm across in the matrix of mica-rich carbonaceous garnet schist may represent pseudomorphs after much larger neoblastic diamonds. Thermobarometric calculations for analyzed coexisting garnet + omphacite + phengite from six Maksyutov unit no. 1 mafic eclogites indicate retrograde physical conditions of 610-680 °C, 1.7-2.6 GPa, slightly lower-pressure conditions than the coesite stability field. Complete conversion of diamond to blocky graphite in the mica-rich schists, and recrystallization of coesite to quartz in the schists, quartzofeldspathic gneisses, and eclogite pods reflect relatively slow exhumation from ~110 km depth to upper crustal levels over 60-90 m.y. Phengite inclusions in zircon and garnet hint at modest activity of H2O during prograde UHP metamorphism of the eclogites and mica-poor gneisses. The latter have retained rare, tiny microdiamond inclusions in garnet on decompression. Abundant white mica in the carbonaceous garnet schists probably reflects a C-O-H-N fluid-mediated, kinetically enhanced prograde production of diamond, and efficient obliteration of this phase accompanying leisurely ascent of the subduction complex. In contrast, associated micapoor gneisses and eclogites were relatively dry during exhumation, so retained rare nanocrystalline microdiamond inclusions in garnet.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Partial equilibrium of radiogenic and stable isotope systems in garnet peridotite during ultrahigh-pressure metamorphism
- Experimental determination of Au solubility in rhyolite melt and magnetite: Constraints on magmatic Au budgets
- Surface oxidation of chalcocite (Cu2S) under aqueous (pH = 2–11) and ambient atmospheric conditions: Mineralogy from Cu L- and O K-edge X-ray absorption spectroscopy
- Determination of molar absorptivity of IR fundamental OH-stretching vibration in rhyolitic glasses
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- The structural behavior of Al3+ in peralkaline melts and glasses in the system Na2O-Al2O3-SiO2
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- Carbon isotope “stratigraphy” in a single graphite crystal: Implications for the crystal growth mechanism of fluid-deposited graphite
- Woodruffite: A new Mn oxide structure with 3 × 4 tunnels
- Calderonite, a new lead-iron-vanadate of the brackebuschite group
- Low-temperature microdiamond aggregates in the Maksyutov Metamorphic Complex, South Ural Mountains, Russia
- Crystal structure of protoanthophyllite: A new mineral from the Takase ultramafic complex, Japan
- Crystallization of AlPO4-SiO2 solid solutions from granitic melt and implications for P-rich melt inclusions in pegmatitic quartz
- On the formation of peridotite-derived Os-rich PGE alloys
- Viscosity of hydrous rhyolitic melts inferred from kinetic experiments, and a new viscosity model
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- Cathodoluminescence investigations on the Popigai, Ries, and Lappajärvi impact diamonds
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- Water solubility in carbonatite melts
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- The distribution of zeolites and their effects on the performance of a nuclear waste repository at Yucca Mountain, Nevada, U.S.A.
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- On the thermochemistry of the solid solution between jarosite and its chromate analog
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- Composition, Fe3+/ΣFe, and crystal structure of non-asbestiform and asbestiform amphiboles from Libby, Montana, U.S.A.
- A rapid and accurate procedure for the determination of refractive indices of regulated asbestos minerals
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Articles in the same Issue
- Partial equilibrium of radiogenic and stable isotope systems in garnet peridotite during ultrahigh-pressure metamorphism
- Experimental determination of Au solubility in rhyolite melt and magnetite: Constraints on magmatic Au budgets
- Surface oxidation of chalcocite (Cu2S) under aqueous (pH = 2–11) and ambient atmospheric conditions: Mineralogy from Cu L- and O K-edge X-ray absorption spectroscopy
- Determination of molar absorptivity of IR fundamental OH-stretching vibration in rhyolitic glasses
- The effect of radiation damage on local structure in the crystalline fraction of ZrSiO4: Investigating the 29Si NMR response to pressure in zircon and reidite
- The structural behavior of Al3+ in peralkaline melts and glasses in the system Na2O-Al2O3-SiO2
- Hydromaghemite, an intermediate in the hydrothermal transformation of 2-line ferrihydrite into hematite
- Carbon isotope “stratigraphy” in a single graphite crystal: Implications for the crystal growth mechanism of fluid-deposited graphite
- Woodruffite: A new Mn oxide structure with 3 × 4 tunnels
- Calderonite, a new lead-iron-vanadate of the brackebuschite group
- Low-temperature microdiamond aggregates in the Maksyutov Metamorphic Complex, South Ural Mountains, Russia
- Crystal structure of protoanthophyllite: A new mineral from the Takase ultramafic complex, Japan
- Crystallization of AlPO4-SiO2 solid solutions from granitic melt and implications for P-rich melt inclusions in pegmatitic quartz
- On the formation of peridotite-derived Os-rich PGE alloys
- Viscosity of hydrous rhyolitic melts inferred from kinetic experiments, and a new viscosity model
- Geothermobarometry and U-Pb Geochronology of metapelitic granulites and pelitic migmatites from the Lokoho region, Northern Madagascar
- The aperiodic states of zircon: an ab initio molecular dynamics study
- Cathodoluminescence investigations on the Popigai, Ries, and Lappajärvi impact diamonds
- Isomorphous cation substitution in dioctahedral phyllosilicates by means of ab initio quantum mechanical calculations on clusters
- Alacranite, As8S9: structural study of the holotype and re-assignment of the original chemical formula
- Influence of layer charge on the hydroxyl stretching of trioctahedral clay minerals: A vibrational study of synthetic Na- and K-saponites
- Stacking faults and twin boundaries in sphalerite crystals from the Trepcˇa mines in Kosovo
- Letters. Rock-forming moissanite (natural α-silicon carbide)
- Water solubility in carbonatite melts
- Trace element partitioning between mantle wedge peridotite and hydrous MgO-rich melt
- Rubidium- and cesium-dominant micas in granitic pegmatites
- Nanoscale mineralogy of arsenic in a region of New Hampshire with elevated As-concentrations in the groundwater
- Micro- and nanochemistry of fly ash from a coal-fired power plant
- Thermal behavior of dental enamel and geologic apatite: An infrared spectroscopic study
- Black carbon pollution of speleothems by fine urban aerosols in tourist caves
- Decay-induced biomineralization of the saguaro cactus (Carnegiea gigantea)
- The distribution of zeolites and their effects on the performance of a nuclear waste repository at Yucca Mountain, Nevada, U.S.A.
- Transformation of 2-line ferrihydrite to 6-line ferrihydrite under oxic and anoxic conditions
- Iron-rich precipitates in a mine drainage environment: Influence of pH on mineralogy
- Efflorescent iron sulfate minerals: Paragenesis, relative stability, and environmental impact
- Secondary mineralogy and microtextures of weathered sulfides and manganoan carbonates in mine waste-rock dumps, with implications for heavy-metal fixation
- Acquisition and evaluation of thermodynamic data for morenosite-retgersite equilibria at 0.1 MPa
- On the thermochemistry of the solid solution between jarosite and its chromate analog
- The Composition and Morphology of Amphiboles from the Rainy Creek Complex, Near Libby, Montana
- Composition, Fe3+/ΣFe, and crystal structure of non-asbestiform and asbestiform amphiboles from Libby, Montana, U.S.A.
- A rapid and accurate procedure for the determination of refractive indices of regulated asbestos minerals
- Ferrous saponite from the Deccan Trap, India, and its application in adsorption and reduction of hexavalent chromium
- Nanomorphology of montmorillonite particles: Estimation of the clay edge sorption site density by low-pressure gas adsorption and AFM observations
- Medieval stained glass in a Mediterranean climate: Typology, weathering and glass decay, and associated biomineralization processes and products
- The structure of disordered mackinawite
- The reactivity of seven Mn-oxides with Cr3+aq: A comparative analysis of a complex, environmentally important redox reaction
- Sorption mechanisms of Sr and Pb on zeolitized tuffs from the Nevada test site as a function of pH and ionic strength
- Letters. Tailoring calcite: Nanoscale AFM of coccolith biocrystals