Precipitation of rutile and ilmenite needles in garnet: Implications for extreme metamorphic conditions in the Acadian Orogen, U.S.A.

Ti–in–garnet thermometer for ultrahigh–temperature granulites

“…The number of Si atoms monotonically decreases by the relation N Si = 3 − N Ti with increasing number of Ti atoms. Although the present experiments show Si decreases but Al keeps constant, Ague and Eckert (2012) reported amounts of Si and Al in garnet decrease with increasing Ti content from granulite facies metapelitic rocks of the Merrimack synclinorium, Connecticut. The discrepancy in the trend of Al may be due to the (Na z M 3−z )[Ti z Al 2−z ]{Si 1−y Ti y }O 12 component in Connecticut garnet with suggestive evidences for ultrahigh-pressure metamorphism at pressures above the quartz-coesite transition predated the granulite facies metamorphism (Ague and Eckert, 2012 Here, it is worth to recall our model that the Ti occupation is restricted only to octahedral site in garnet.…”

“…Rutile needles have been reported in pyroxenes and garnet in rocks formed at a wide range of extreme pressuretemperature conditions, for example, high-pressure layered intrusions (Moore, 1968), ultrahigh-pressure eclogites (Mposkos and Kostopoulos, 2001;Hwang et al, 2007;Griffin, 2008) and peridotites as well as ilmenite rods in olivine (Green et al, 1997;Dobrzhinetskaya et al, 2000;Song et al, 2004), high-pressure granulite (Ague and Eckert, 2012), ultrahigh-pressure granulite (Larsen et al, 1998) and ultrahigh-temperature granulites (Moraes et al, 2002). We often find the exsolution lamellae of rutile in the porphyroblastic garnet, orthopyroxene, sapphirine, osumilite, K-feldspar (mesoperthite) and quartz of the ultrahigh-temperature granulites from Napier complex, East Antarctica (Kawasaki and Motoyoshi, 2000;Osanai et al, 2001).…”

Cathodoluminescence guided zircon Hf isotope depth profiling: Mobilization of the Lu–Hf system during (U)HP rock exhumation in the Woodlark Rift, Papua New Guinea

“…For example, Spacek et al (2013) documented the breakdown of mantle garnet during rapid exhumation in the Bohemian Massif, and there is evidence that the release of Ti (Ague and Eckert, 2012;Zhang et al, 2003) and Zr (Degeling et al, 2001), both of which are geochemically similar to Hf, from garnet can occur during decompression of the mantle. Therefore, it is possible that the Hf isotopic signature of the zircon overgrowths in sample 03-118m originated from liberation of radiogenic Hf by breakdown of garnet during rifting related rapid decompression (Fig.…”

“…Instead, a medium derived from the wholesale breakdown of mantle garnet (e.g. Ague and Eckert, 2012;Degeling et al, 2001;Spacek et al, 2013;Zhang et al, 2003) due to aesthenospheric upwelling (Abers et al, 2002) in the Woodlark Rift, or eclogite garnet during rapid exhumation, better explains the Lu-Hf isotope systematics of the some of the zircon domains within sample 08-010g.…”

External and internal features of garnet revealed by the multifocus imaging technique

“…Andò et al, 2012). Studies of fluid inclusions (Ague and Eckert, 2012;Van den Kerkhof and Hein, 2001;Vry and Brown, 1991) and melt and glassy inclusions (e.g. Acosta-Vigil et al, 2007;Cesare, 2008) are important in the reconstruction of a rock geologic evolution.…”