Nomenclature of amphiboles: additions and revisions to the International Mineralogical Association's amphibole nomenclature

Leake, Bernard Elgey; Woolley, A. R.; Birch, William D.; Burke, E. A. J.; Ferraris, Giovanni; Grice, Joel D.; Hawthorne, Frank C.; Kisch, Hanan J.; Кривовичев, В. Г.; Schumacher, John C.; Stephenson, N. C. N.; Whittaker, E. J. W.

doi:10.1127/0935-1221/2004/0016-0191

Cited by 103 publications

(64 citation statements)

References 11 publications

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“…Following the classification scheme of Leake et al (1997Leake et al ( , 2003 for calcic amphiboles (Ca B 1.50; (Na 1 K) A 0.50, where A and B are cation sites), amphibole compositions in our experiments are pargasitic (Table 3), i. e., Si 6.0 to 6.5 and [Mg/(Mg 1 Fe)] 0.89-0.92 (where Si, Mg, and Fe are expressed in terms of atoms per formula unit based on 23 oxygens). Mg# of amphibole varies from 91.3 to 92.1 in Bulk 1 and 91.5 to 92.5 in Bulk 2 (Table 3) and do not show much compositional variability.…”

Section: Amphibolementioning

confidence: 99%

High Pressure Phase Relations of a Depleted Peridotite Fluxed by CO₂‐H₂O‐Bearing Siliceous Melts and the Origin of Mid‐Lithospheric Discontinuity

Saha

Dasgupta

Tsuno

2018

Geochem Geophys Geosyst

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We present phase equilibria experiments on a depleted peridotite (Mg# 92) fluxed with variable proportions of a slab‐derived rhyolitic melt (with 9.4 wt.% H2O, 5 wt.% CO2), envisaging an interaction that could occur during formation of continents by imbrication of slabs/accretion of subarc mantles. Experiments were performed with 5 wt.% (Bulk 2) and 10 wt.% (Bulk 1) melt at 950–1175°C and 2–4 GPa using a piston‐cylinder and a multi‐anvil apparatus, to test the hypothesis that volatile‐bearing mineral‐phases produced during craton formation can cause reduction in aggregate shear‐wave velocities (VS) at mid‐lithospheric depths beneath continents. In addition to the presence of olivine, orthopyroxene, clinopyroxene, and garnet/spinel, phlogopite (Bulk 1: 3–7.6 wt.%; Bulk 2: 2.6–5 wt.%) at 2–4 GPa, and amphibole (Bulk 1: 3–9 wt.%; Bulk 2: 2–6 wt.%) at 2–3 GPa (≤1050°C) are also present. Magnesite (Bulk 1: ∼1 wt.% and Bulk 2: ∼0.6 wt.%) is present at 2–4 GPa (<1000°C at 3 and < 1050°C at 4 GPa) and its thermal breakdown coincides with the visual appearance of trace‐melt. However, an extremely small fraction of melt is inferred at all experiments based on the knowledge of fluid‐saturated peridotite solidus and the difference between bulk H2O and total H2O stored in the hydrous phases. Calculated mineral end‐member volume‐proportions were used to calculate VS of the resulting assemblage at experimental conditions and along representative continental geotherms (surface heat flow of 40–50 mWm−2). We note that reactive crystallization of phlogopite ± amphibole by infiltration of 3–10% slab‐derived hydrous‐silicic melt can cause up to 6% reduction in VS and that the estimated reduction in VS increases with increasing melt:rock ratio. The presence of phlogopite limits amphibole‐stability, making phlogopite a more likely candidate for MLDs at >100 km depth.

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Section: Amphibolementioning

confidence: 99%

High Pressure Phase Relations of a Depleted Peridotite Fluxed by CO₂‐H₂O‐Bearing Siliceous Melts and the Origin of Mid‐Lithospheric Discontinuity

Saha

Dasgupta

Tsuno

2018

Geochem Geophys Geosyst

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“…Amphibole in the host WFO is pargasite using the classification of Leake et al (1997Leake et al ( , 2004 with X Fe = 0.39-0.44. It is uniform in composition except where it is partially pseudomorphing pyroxene; here the amphibole is still pargasite, but with 2 wt% oxide increases in SiO 2 and CaO, and decreases in Al 2 O 3 (2 wt% oxide), FeO (1 wt% oxide; X Fe = 0.41) and K 2 O (0.8 wt% oxide), relative to the separate large grains.…”

Section: Whole-rock Geochemistry and Mineral Chemistrymentioning

confidence: 99%

Evidence for melt migration enhancing recrystallization of metastable assemblages in mafic lower crust, Fiordland, New Zealand

Daczko¹,

Halpin

2009

Journal Metamorphic Geology

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A major arc batholith, the Western Fiordland Orthogneiss (WFO) in Fiordland, New Zealand, exhibits irregular, spatially restricted centimetre-scale recrystallization from two-pyroxene hornblende granulite to garnet granulite flanking felsic dykes. At Lake Grave, northern Fiordland, the composition and texture of narrow (<10-20 mm across) felsic dykes that cut the orthogneiss are consistent with an igneous origin and injection of melt to form orthogneiss migmatite. New U-Pb geochronology suggests that the injection of dykes and migmatization occurred at c. 115 Ma, during the later stages of arc magmatism. Recrystallization to garnet granulite is promoted by volatile extraction from the host twopyroxene hornblende granulite via adjacent dykes and the patchy development of garnet granulite is left as a marker adjacent to the melt migration path. New mineral equilibria modelling suggests that a twopyroxene hornblende assemblage is stable at <11 kbar, whereas a garnet granulite assemblage is stable at >12 kbar, suggesting that garnet granulite may have formed with <5 km crustal loading of the batholith. Although the garnet granulite assemblages signify that the WFO experienced high-P conditions, the very local nature of these textures indicates widespread metastability (>90%) of the twopyroxene hornblende granulite assemblages. These results indicate the strongly metastable nature of assemblages in mafic lower arc crust during deep burial and demonstrate that the degree of reaction in the case of Fiordland is related to interaction with migrating melts.

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“…Sample 2049B is a Hbl, Pl, Qz, Cpx, Grt, Ilm amphibolite (Figures 3 and 4f). Amphibole (Mg# = 0.53-0.57, (Na+K) A = 0.47-0.52, Si a.p.f.u = 6.5; Table 1) accounts for 50 mode% of the rock and varies in composition from tschermakite to edenite (classification after Leake et al, 2004). Cahornblende is observed in matrix and Fe-hornblende occurs around clinopyroxene (Fe# = 0.34-0.37, Na = 0.02 a.p.f.u., Ca = 0.9 a.p.f.u).…”

Section: Sample 2049bmentioning

confidence: 99%

Complete metamorphic cycle and long‐lived anatexis in the c. 2.1 Ga Mistinibi Complex, Canada

Godet

Guilmette

Labrousse

et al. 2020

Journal Metamorphic Geology

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Secular changes in the architecture, thermal state, and metamorphic style of global orogens are thought to have occurred since the Archean; however, despite widespread research, the driving mechanisms for such changes remain unclear. The Paleoproterozoic may prove to be a key era for investigating secular changes in global orogens, as it marks the earliest stage of an eon that saw the onset of modern‐style global tectonics. The 2.1 Ga granulite‐facies Mistinibi‐Raude Domain (MRD), located in the Southeastern Churchill Province, Canada, offers a rare exposure of Paleoproterozoic high metamorphic grade supracrustal sequences (Mistinibi Complex, MC). Rocks from this domain were subjected to petrochronological investigations to establish P–T–t–X evolutions and to provide first order thermal state, burial and exhumation rates, and metamorphic gradients for the transient Paleoproterozoic times. To obtain comprehensive insight into the P–T–t–X evolution of the MRD, we used multi‐method geochronology—Lu–Hf on garnet and U–Pb on zircon and monazite—integrated with detailed petrography, trace element chemistry, and phase equilibria modelling. Despite the extensive use of zircon and monazite as geochronometers, their behaviour in anatectic conditions is complex, leading to substantial ambiguity in interpreting the timing of prograde metamorphism. Our results indicate a clockwise metamorphic path involving significant melt extraction from the metasedimentary rocks, followed by cooling from >815°C to ~770°C at ~0.8 GPa. The timing of prograde burial and cooling from supra‐ to subsolidus conditions is constrained through garnet, monazite, and zircon petrochronology at 2,150–2,120 Ma and at 2,070–2,080 Ma, respectively. These results highlight long‐lived residence of the rocks at mid‐crustal supra‐solidus conditions (55–70 Ma), with preserved prograde and retrograde supra‐solidus monazite and zircon. The rocks record extremely slow burial rates (0.25–0.30 km/Ma) along a high metamorphic gradient (900–1,000°C/GPa), which appears symptomatic of Paleoproterozoic orogens. The MC did not record any significant metamorphism after 2,067 Ma, despite having collided with terranes that record high‐grade metamorphism during the major 1.9–1.8 Ga Trans‐Hudson orogeny. The MC would therefore represent a remnant of a local early Paleoproterozoic metamorphic infrastructure, later preserved as superstructure in the large hot Trans‐Hudson orogen.

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Nomenclature of amphiboles: additions and revisions to the International Mineralogical Association's amphibole nomenclature

Cited by 103 publications

References 11 publications

High Pressure Phase Relations of a Depleted Peridotite Fluxed by CO₂‐H₂O‐Bearing Siliceous Melts and the Origin of Mid‐Lithospheric Discontinuity

High Pressure Phase Relations of a Depleted Peridotite Fluxed by CO₂‐H₂O‐Bearing Siliceous Melts and the Origin of Mid‐Lithospheric Discontinuity

Evidence for melt migration enhancing recrystallization of metastable assemblages in mafic lower crust, Fiordland, New Zealand

Complete metamorphic cycle and long‐lived anatexis in the c. 2.1 Ga Mistinibi Complex, Canada

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Nomenclature of amphiboles: additions and revisions to the International Mineralogical Association's amphibole nomenclature

Cited by 103 publications

References 11 publications

High Pressure Phase Relations of a Depleted Peridotite Fluxed by CO2‐H2O‐Bearing Siliceous Melts and the Origin of Mid‐Lithospheric Discontinuity

High Pressure Phase Relations of a Depleted Peridotite Fluxed by CO2‐H2O‐Bearing Siliceous Melts and the Origin of Mid‐Lithospheric Discontinuity

Evidence for melt migration enhancing recrystallization of metastable assemblages in mafic lower crust, Fiordland, New Zealand

Complete metamorphic cycle and long‐lived anatexis in the c. 2.1 Ga Mistinibi Complex, Canada

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Product

Resources

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High Pressure Phase Relations of a Depleted Peridotite Fluxed by CO₂‐H₂O‐Bearing Siliceous Melts and the Origin of Mid‐Lithospheric Discontinuity

High Pressure Phase Relations of a Depleted Peridotite Fluxed by CO₂‐H₂O‐Bearing Siliceous Melts and the Origin of Mid‐Lithospheric Discontinuity