Precipitation of rutile and ilmenite needles in garnet: Implications for extreme metamorphic conditions in the Acadian Orogen, U.S.A.
-
Jay J. Ague
and
James O. Eckert
Abstract
We report the discovery of oriented needles of rutile and ilmenite in garnet crystals from granulite facies metapelitic rocks of the Merrimack synclinorium. Connecticut, and present a precipitation model for their origin. The rocks were strongly metamorphosed and deformed during the Devonian Acadian orogeny. The needles are primarily elongated parallel to <111> in garnet. Rutile has anomalous extinction angles as great as ~35° (cf. Griffin et al. 1971). Rutile and ilmenite needles are typically a few hundred nanometers to several micrometers in diameter and are several tens of micrometers to nearly a millimeter long. Other oxide inclusions that may be present include submicrometer- to micrometer-scale twinned rutile bicrystals, as well as srilankite and a crichtonite group mineral. Some garnet cores have unusual, box-shaped quartz inclusions, which coexist with Ti±Fe oxide needles and commonly contain micrometer-scale rods of F-OH-C1 apatite. Negative garnet ciystal "pores” are also widespread. Ti±Fe oxide needles are restricted to garnet core regions; rims have a distinctly different inclusion population dominated by granulite facies minerals including sillimanite, spinel, cordierite, and K-feldspar. Consequently, the garnet core regions represent an earlier, distinct period of growth relative to the rims. Garnet cores contain ~25-35% pyrope. and a host of minor and trace constituents including TiO2 (0.07-0.6 wt%). Cr203 (0.01-0.10 wt%). Na2O (0.01-0.03 wt%). P2O5 (0.01-0.09 wt%). and ZrO2 (up to -150 ppm). Na2O and ZrO2 correlate positively with TiO2.Titanium zoning is preserved in some garnets; zoning profiles and two-dimensional chemical mapping show' that Ti and. to a lesser degree. Cr are depleted around Ti±Fe oxide inclusions. Therefore, we conclude that the needles are precipitates that formed from Ti-bearing garnet during exhumation and cooling. Garnet contained sufficient Ti to form precipitates; no Ti source external to garnet was necessary. Titaniumbearing garnets that contain oriented Ti±Fe oxide needles are known primarily from ultrahigh-pressure metamorphic rocks, mantle peridotites and pyroxenites, and high-pressure granulites. Thus, the presence of needle-bearing garnets in Connecticut strongly suggests that a previously unrecognized domain of extreme pressure and/or temperature metamorphism exists in the Acadian orogen.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Dana medal lecture: Tilts and tetrahedra: The origin of the anisotropy of feldspars
- Amorphous Materials: Determination of water content in silicate glasses using Raman spectrometry: Implications for the study of explosive volcanism
- Density functional calculations of the enthalpies of formation of rare-earth orthophosphates
- U-Pb ID-TIMS dating applied to U-rich inclusions in garnet
- Wassonite: A new titanium monosulfide mineral in the Yamato 691 enstatite chondrite
- Determination of Mn valence states in mixed-valent manganates by XANES spectroscopy
- The morphology of the reaction front of the dissolutionprecipitation reaction rutile + wollastonite = titanite in time series experiments at 600 °C/400 MPa
- Precipitation of rutile and ilmenite needles in garnet: Implications for extreme metamorphic conditions in the Acadian Orogen, U.S.A.
- The genesis of mantle-derived sapphirine
- Experimental investigation of smectite interaction with metal iron at 80 °C: Structural characterization of newly formed Fe-rich phyllosilicates
- High-pressure study of a natural cancrinite
- Investigation of cation ordering in triclinic sodium birnessite via 23Na MAS NMR spectroscopy
- The dual behavior of the β-As4S4 altered by light
- Pressure-induced changes in local electronic structures of SiO2 and MgSiO3 polymorphs: Insights from ab initio calculations of O K-edge energy-loss near-edge structure spectroscopy
- Structural stability, cation ordering, and local relaxation along the AlNbO4-Al0.5Cr0.5NbO4 join
- Europium oxidation state and local structure in silicate glasses
- Kinetics of partial dehydroxylation in dioctahedral 2:1 layer clay minerals
- Determination of Fe3+/Fe using the electron microprobe: A calibration for amphiboles
- Characterization of smectite to NH4-illite conversion series in the fossil hydrothermal system of Harghita Bãi, East Carpathians, Romania
- Allanite-(Nd), CaNdAl2Fe2+(SiO4)(Si2O7)O(OH), a new mineral from Åskagen, Sweden
- Tsilaisite, NaMn3Al6(Si6O18)(BO3)3(OH)3OH, a new mineral species of the tourmaline supergroup from Grotta d’Oggi, San Pietro in Campo, island of Elba, Italy
- Letter. A nanoscopic approach to the kinetics of anhydrite (100) surface growth in the range of temperatures between 60 and 120 °C
- Letter. High-pressure phase transitions in Ca-Mn carbonates (Ca,Mn)CO3 studied by Raman spectroscopy
- Letter. Actinides in Geology, Energy, and the Environment: Thermally induced transformation of vorlanite to “protovorlanite”: Restoration of cation ordering in self-irradiated CaUO4
Articles in the same Issue
- Dana medal lecture: Tilts and tetrahedra: The origin of the anisotropy of feldspars
- Amorphous Materials: Determination of water content in silicate glasses using Raman spectrometry: Implications for the study of explosive volcanism
- Density functional calculations of the enthalpies of formation of rare-earth orthophosphates
- U-Pb ID-TIMS dating applied to U-rich inclusions in garnet
- Wassonite: A new titanium monosulfide mineral in the Yamato 691 enstatite chondrite
- Determination of Mn valence states in mixed-valent manganates by XANES spectroscopy
- The morphology of the reaction front of the dissolutionprecipitation reaction rutile + wollastonite = titanite in time series experiments at 600 °C/400 MPa
- Precipitation of rutile and ilmenite needles in garnet: Implications for extreme metamorphic conditions in the Acadian Orogen, U.S.A.
- The genesis of mantle-derived sapphirine
- Experimental investigation of smectite interaction with metal iron at 80 °C: Structural characterization of newly formed Fe-rich phyllosilicates
- High-pressure study of a natural cancrinite
- Investigation of cation ordering in triclinic sodium birnessite via 23Na MAS NMR spectroscopy
- The dual behavior of the β-As4S4 altered by light
- Pressure-induced changes in local electronic structures of SiO2 and MgSiO3 polymorphs: Insights from ab initio calculations of O K-edge energy-loss near-edge structure spectroscopy
- Structural stability, cation ordering, and local relaxation along the AlNbO4-Al0.5Cr0.5NbO4 join
- Europium oxidation state and local structure in silicate glasses
- Kinetics of partial dehydroxylation in dioctahedral 2:1 layer clay minerals
- Determination of Fe3+/Fe using the electron microprobe: A calibration for amphiboles
- Characterization of smectite to NH4-illite conversion series in the fossil hydrothermal system of Harghita Bãi, East Carpathians, Romania
- Allanite-(Nd), CaNdAl2Fe2+(SiO4)(Si2O7)O(OH), a new mineral from Åskagen, Sweden
- Tsilaisite, NaMn3Al6(Si6O18)(BO3)3(OH)3OH, a new mineral species of the tourmaline supergroup from Grotta d’Oggi, San Pietro in Campo, island of Elba, Italy
- Letter. A nanoscopic approach to the kinetics of anhydrite (100) surface growth in the range of temperatures between 60 and 120 °C
- Letter. High-pressure phase transitions in Ca-Mn carbonates (Ca,Mn)CO3 studied by Raman spectroscopy
- Letter. Actinides in Geology, Energy, and the Environment: Thermally induced transformation of vorlanite to “protovorlanite”: Restoration of cation ordering in self-irradiated CaUO4
