A garnet–hornblende geothermometer: calibration, testing, and application to the Pelona Schist, Southern California

Graham, Colin M.; Powell, Roger

doi:10.1111/j.1525-1314.1984.tb00282.x

Cited by 693 publications

(401 citation statements)

References 57 publications

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“…P-T conditions have been calculated using grt + amp thermometry (Graham and Powell, 1984;Ravna, 2000) and geobarometers for the amphibole-bearing assemblage (Kohn and Spear, 1990), utilizing symplectic amphibole, plagioclase, and the resetting of garnet-rim (grt R2 ) compositions. Four grt + amp + pl + qtz determinations from the two samples (P552b5, L1201b1) yielded a P-T range of 0.62-0.82 GPa and 590-650 • C (Table S6), representing the P-T conditions during the late amphibolite facies retrograde stage (M 3 ) in the Xiangtaohu HP basic granulites.…”

Section: Late Amphibolite-facies Retrograde Stage (M 3 )mentioning

confidence: 99%

Silurian high-pressure granulites from Central Qiangtang, Tibet: Constraints on early Paleozoic collision along the northeastern margin of Gondwana

Zhang

Dong

Cai

et al. 2014

Earth and Planetary Science Letters

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Section: Late Amphibolite-facies Retrograde Stage (M 3 )mentioning

confidence: 99%

Silurian high-pressure granulites from Central Qiangtang, Tibet: Constraints on early Paleozoic collision along the northeastern margin of Gondwana

Zhang

Dong

Cai

et al. 2014

Earth and Planetary Science Letters

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“…On the ACF-deluxe chemography in Figure 6 (Thompson 1982), where the composition of calculated pre-Alpine amphibolite-facies minerals is reported, bulk Mineral abbreviations are as proposed by Kretz (1983). O = Ti content in amphibole according to Otten (1984); P = garnet/amphibole Fe-Mg exchange according to Perchuk (1991); GP = garnet/amphibole Fe-Mg exchange according to Graham and Powell (1984); EGP = garnet/clinopyroxene Fe-Mg exchange according to Ellis and Green (1979) after (Powell 1985); K = garnet/clinopyroxene Fe-Mg exchange according to Krogh Ravna (2000); K&R = garnet/white mica Fe-Mg exchange according to Krogh and Råheim (1978); PS = amphibole compositions experimentally determined during amphibolites-to-eclogite transition according to Poli (1993) and Schmidt (1993); S = white mica compositions experimentally determined during amphibolites-to-eclogite transition according to Schmidt (1993); HZ, H, JR = Al tot content in amphibole according to Hammarstrom and Zen (1986), Hollister et al (1987), and Johnson and Rutherford (1989), respectively. compositions are aligned along the join between plagioclase and hornblende, as expected for amphibolite-facies metabasites. This suggests that different modal amounts of hornblende and plagioclase, and the accompanying minerals diopside, orthopyroxene, biotite, and quartz, characterized the pre-eclogitic assemblage.…”

Section: Bulk Chemistry Versus Modal Compositionmentioning

confidence: 99%

Interplay between deformation and metamorphism during eclogitization of amphibolites in the Sesia–Lanzo Zone of the Western Alps

Gosso

Messiga

Rebay

et al. 2010

International Geology Review

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Interactions of fabric evolution and chemical parameters driving reaction progress during the amphibolite-to-eclogite transition were investigated in eclogitized amphibolites of the Western Alps. In the Sesia-Lanzo Zone (SLZ), mafic rocks ranging from eclogitized hornblendites to true eclogites occur as layers and boudins within micaschists and are characterized by different modal amounts of amphibole, omphacite, zoisite, garnet, and phengite, constituting the Alpine HP assemblage. Across narrow zones, this array of lithologies displays gradients in planar fabrics characterized by coronitic, S-tectonitic, and mylonitic textures with different extents of eclogitization. Eclogitic parageneses are controlled not only by the bulk rock composition of the protoliths but also by the degree of fabric evolution. This is the case for omphacite occurrence, which is constrained by plagioclase composition and modal amount (NK parameter) in the protoliths, whereas the increase in modal omphacite and the concomitant decrease in modal amphibole in rocks with high NK are controlled by the strain rate. Protoliths with a low NK content develop the amphibole + garnet + epidote assemblage in eclogitized hornblendites. In protoliths with higher NK values, the co-existence of amphibole with garnet, omphacite, and epidote occurs only for low-to-medium strain textures (e.g. coronites and S-tectonites), whereas an amphibole-free assemblage defines a mylonitic foliation; in this case, amphibole relics are present exclusively as armoured inclusions in garnets and omphacite porphyroclasts. Thus, amphibole persists in the eclogitic assemblage at pressures exceeding the experimentally determined amphibole stability field. Values of confining pressure under which Sesia-Lanzo mafic rocks re-equilibrated during Alpine subduction were estimated, through equilibrium assemblage modelling, at 2.2-2.7 GPa. The amphibole-bearing eclogites of the SLZ show that large volumes of amphibole-bearing rocks can be exhumed from a depth exceeding 75 km without dehydration reactions running to completion. Petrological estimates in orogenic zones may help constrain geological and tectonic conclusions when selection of laboratory samples is assisted even by simple microstructural evaluation of planar fabric development.

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“…This effect is probably mainly due to inheritance from igneous conditions, with growth of adjacent garnet affecting only the rims of relict igneous grains. [Graham and Powell, 1984] were applied to five metagabbros and two garnet-bearing tonalites (Table 5). The three samples from the Tunis Creek metagabbro gave very similar temperatures of 580ø-590øC, while the other two metagabbros, GC-46 from Liveoak Canyon (760 ø) and GVl a from Grapevine Canyon (700ø), record significantly higher temperatures.…”

Section: Plagioclasementioning

confidence: 99%

Thermobarometric constraints on the depth of exposure and conditions of plutonism and metamorphism at deep levels of the Sierra Nevada Batholith, Tehachapi Mountains, California

Pickett¹,

Saleeby²

1993

J. Geophys. Res.

100

109

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We present thermodynamic estimates of pressures, temperatures, and volatile activities in vailably deformed, gabbroic to granitic, Cretaceous (115-100 Ma) batholithic and framework rocks of the Tehachapi Mountains, southernmost Sierra Nevada, California. A1 contents of hornblende in granitoids imply igneous emplacement at --8 kbar in the southernmost Tehachapi Mountains, with lower pressures (3-7 kbar) to the north. Metamorphic pressures and temperatures for garnet-bearing paragneisses and metaigneous rocks were estimated on the basis of garnet-homblende-plagioclase-quartz and garnet-biotiteplagioclase-quartz thermobarometers. Disparate results for the metaigneous rocks from the latter system point to the difficulty of applying pelite-based thermobarometers to rocks of contrasting composition and mineralogy. Preferred pressures cluster at 7.1-9.4 and 3.6-4.3 kbar. Incomplete knowledge of reaction histories, however, limits our interpretation of the lower pressures because they are minimum estimates. The --4-kbar samples are all from a small area and, if our interpretation is correct, they imply a local, more shallow event superimposed on crust once residing at deeper structural levels. Garnet-hornblende and garnet-biotite temperatures are less coherent, likely owing to retrograde Fe-Mg exchange, and range from 570 ø to 790øC. The majority of the rocks are igneous and affected by recrystallization and metamorphism during subsolidus cooling; they are not granulites. Country rock paragneisses are typically migmatized at "peak" metamorphic conditions near that of the wet granite solidus (>690øC). Veinlike paragenesis of garnet in the metaigneous rocks suggests formation related to the presence of a fluid phase. Thermodynamic estimates of volatile activities in these garnet-bearing assemblages suggest variable, mostly CO 2-rich fluid compositions, in the absence of any pervasive fluid flux. The igneous rocks of the Tehachapi Mountains were thus intruded at depths of --30 km, making them the deepest known exposed components of the Cretaceous Sierra Nevada batholith. Metamorphism occurred at these great depths and, perhaps, locally after --15 km of uplift before --87 Ma, implying an uplift rate of 1.2 mm/yr. (A minimum uplift rate is 0.6 mm/yr.) This original uplift and possible subsequent uplift events may have been related to underthrusting of a block of Rand Schist from what is now the southeast, with concomitant widespread ductile deformation. The deduced pressure-temperature and uplift history is similar to those of highpressure/high-temperature Cretaceous batholithic rocks in Salinia and the San Gabriel Mountains, but direct correlation is not wan-anted. When compared with higher-level intrusive rocks from analogous portions of the Sierra Nevada batholith to the north, the Tehachapi rocks reveal a deep batholith that is more heterogeneous and somewhat more mafic on average, but displaying a similar level of isotopic hybridization involving mantle and crustal sources. The batholith is quartz-rich at these levels, ...

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A garnet–hornblende geothermometer: calibration, testing, and application to the Pelona Schist, Southern California

Cited by 693 publications

References 57 publications

Silurian high-pressure granulites from Central Qiangtang, Tibet: Constraints on early Paleozoic collision along the northeastern margin of Gondwana

Silurian high-pressure granulites from Central Qiangtang, Tibet: Constraints on early Paleozoic collision along the northeastern margin of Gondwana

Interplay between deformation and metamorphism during eclogitization of amphibolites in the Sesia–Lanzo Zone of the Western Alps

Thermobarometric constraints on the depth of exposure and conditions of plutonism and metamorphism at deep levels of the Sierra Nevada Batholith, Tehachapi Mountains, California

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