Chemical evolution of high-grade metamorphic rocks — Anatexis and remotion of material from granulite terrains

Sighinolfi, G. P.; Gorgoni, C.

doi:10.1016/0009-2541(78)90029-3

Cited by 67 publications

(13 citation statements)

References 32 publications

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“…Indeed, partial melting of deeper crustal rocks is the major process of crustal differentiation and, eventually through erosion, cratonisation (e.g. Lambert and Heier, 1968;Fyfe, 1973b;Sighinolfi and Gorgoni, 1978;Vielzeuf et al, 1990;Sandiford et al, 2001Solar and Brown, 2001;Brown and Rushmer, 2006;Brown, 2010a;Sandiford, 2010;Sawyer et al, 2011;Jamieson and Beaumont, 2013). The process of melt loss is critical to the preservation of granulite facies mineral assemblages (Brown and Fyfe, 1970;Fyfe, 1973b;McCarthy, 1976;O'Hara et al, 1978;Powell, 1983;Powell and Downes, 1990;Sawyer, 1994;Brown, 2002;Guernina and Sawyer, 2003) as melt loss dehydrates the rock mass and inhibits retrogression during cooling.…”

Section: Compositions For Pseudosection Calculationsmentioning

confidence: 97%

On ultrahigh temperature crustal metamorphism: Phase equilibria, trace element thermometry, bulk composition, heat sources, timescales and tectonic settings

Kelsey

Hand

2015

Geoscience Frontiers

349

285

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a b s t r a c tUltrahigh temperature (UHT) metamorphism is the most thermally extreme form of regional crustal metamorphism, with temperatures exceeding 900 C. UHT crustal metamorphism is recognised in more than 50 localities globally in the metamorphic rock record and is accepted as 'normal' in the spectrum of regional crustal processes. UHT metamorphism is typically identified on the basis of diagnostic mineral assemblages such as sapphirine þ quartz, orthopyroxene þ sillimanite AE quartz and osumilite in MgeAlrich rock compositions, now usually coupled with pseudosection-based thermobarometry using internally-consistent thermodynamic data sets and/or Al-in-Orthopyroxene and ternary feldspar thermobarometry. Significant progress in the understanding of regional UHT metamorphism in recent years includes: (1) development of a ferric iron activityecomposition thermodynamic model for sapphirine, allowing phase diagram calculations for oxidised rock compositions; (2) quantification of UHT conditions via trace element thermometry, with Zr-in-rutile more commonly recording higher temperatures than Ti-in-zircon. Rutile is likely to be stable at peak UHT conditions whereas zircon may only grow as UHT rocks are cooling. In addition, the extent to which Zr diffuses out of rutile is controlled by chemical communication with zircon; (3) more fully recognising and utilising temperature-dependent thermal properties of the crust, and the possible range of heat sources causing metamorphism in geodynamic modelling studies; (4) recognising that crust partially melted either in a previous event or earlier in a long-duration event has greater capacity than fertile, unmelted crust to achieve UHT conditions due to the heat energy consumed by partial melting reactions; (5) more strongly linking UePb geochronological data from zircon and monazite to PeT points or path segments through using Y þ REE partitioning between accessory and major phases, as well as phase diagrams incorporating Zr and REE; and (6) improved insight into the settings and factors responsible for UHT metamorphism via geodynamic forward models. These models suggest that regional UHT metamorphism is, principally, geodynamically related to subduction, coupled with elevated crustal radiogenic heat generation rates.Ó 2014, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

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Section: Compositions For Pseudosection Calculationsmentioning

confidence: 97%

On ultrahigh temperature crustal metamorphism: Phase equilibria, trace element thermometry, bulk composition, heat sources, timescales and tectonic settings

Kelsey

Hand

2015

Geoscience Frontiers

349

285

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“…The observations discussed above can be generally applied to other terrains, and therefore may, in principle, be used to distinguish between the presence and absence of metamorphic fluids. For example, pelitic rocks from the Ivrea zone (northern Italy) underwent fluid‐absent anatexis that broke down muscovite and formed sillimanite and K‐feldspar along with the melt ( Sighinolfi and Gorgoni, 1978). These rocks show no distinct variation in δ 18 O values with increasing metamorphic grade ( Baker, 1990).…”

Section: Other Terrainsmentioning

confidence: 99%

The link between oxygen isotope resetting, partial melting, and fluid flow in metamorphic terrains

Cartwright

Buick

1998

Terra Nova

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A correlation between the style of partial melting and synmeta‐morphic fluid flow exists in metapelites from the Mount Lofty Ranges, Reynolds Range, and Omeo Zone (Australia). Mount Lofty Ranges migmatites comprise granitic leucosomes in rocks that are still biotite rich, with no indications of other mafic minerals being formed along with the melts. By contrast, in the Reynolds and Omeo migmatites, garnet, cordierite, and/or spinel formed along with the melts. Oxygen isotope data are most consistent with the Mount Lofty Ranges undergoing significant fluid–rock interaction during regional metamorphism, which may have fluxed fluid‐present partial melting. By contrast regional metamorphic fluid flow in the Reynolds Range and Omeo Zone was limited, leading to partial melting via fluid‐absent reactions. The style of melting reactions may help to constrain the timing of isotopic resetting and fluid flow in metamorphic terrains, which is currently a contentious issue.

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“…However, as in the case of the B/Be ratio, the low Li/Be values do not preclude the recycled oceanic crust or sediments in the OIB mantle source. Sighinolfi and Gorgoni (1978) found that most of Li in rocks is released during granulite facies metamorphism suggesting that Li is stripped from rocks during subduction. Furthermore, Ryan et al (1989) noted that the Li/Be ratio, like B/Be, decreases away from the arc front indicating that in the subduction zone, Li was released into a hydrous fluid phase that invaded the overlying mantle wedge.…”

Section: Significance Of B/be and Li/be Ratiosmentioning

confidence: 99%

Distribution of boron, lithium and beryllium in ocean island basalts from French Polynesia: implications for the B/Be and Li/Be ratios as tracers of subducted components

1996

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The study focuses on the distribution of B, Be, Li, rare earth elements (REE), high-field-strength elements (HFSE), Th, U and Pb in fresh and hydrothermally altered ocean island basalts (OIB) from French Polynesia, and evaluates B/Be and Li/Be ratios as potential tracers of subducted components in the mantle. Hydrothermal solutions affecting the rocks during cooling were derived from meteoric water, sea water and magmatic fluids. The concentrations of REE, HFSE, Th and Be in the OIB were not affected by secondary processes except during advanced stages of subaerial hydrothermal alteration where saponite was a dominant secondary phase. This alteration modified the contents of these elements, changed REE patterns and produced a positive Ce anomaly. The subaerial and submarine hydrothermal alteration (T ~ 70-100~ may change U concentrations in OIB, whereas Pb was only marginally redistributed during alteration.Boron was enriched during submarine and subaerial hydrothermal alteration but was not noticeably affected in basalts altered by magmatic fluids at T > 200~ Like B, the mobility of Li during the alteration varies with fluid temperature. Lithium became enriched in the basalts during advanced stages of lower T hydrothermal alteration (<100~ However, this element was partly removed from the rocks during higher T alteration (>200~ by magmatic fluids. Boron, Be and Li behave as incompatible trace elements in basaltic magmas. Beryllium content in primitive mantle is estimated to be 0.07 ppm. Fresh Polynesian OIB have low abundances of B and Li and low B/Be (2-5) and Li/Be (2.5-5) ratios compared with volcanic arc rocks, marine sediments and altered oceanic crust. Various OIB including even those which have HIMU-and EMaffinities have similar overlapping B/Be and Li/Be ratios. Both B and Li are probably stripped from a lithospheric slab during subduction-related metamorphism and are, thus, not involved in deep mantle recycling. The mantle-normalized trace element abundances of MORB and OIB usually display patterns characterized by negative B, Pb and Li anomalies. The patterns of continental crust and crustal rocks have distinct positive anomalies for these elements whereas continental basaltic rocks have variable relative abundances of B, Pb and Li. The anomalies of these elements in basalts can be useful in discriminating their tectonic setting and constraining the mantle source regions of basalts.

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Chemical evolution of high-grade metamorphic rocks — Anatexis and remotion of material from granulite terrains

Cited by 67 publications

References 32 publications

On ultrahigh temperature crustal metamorphism: Phase equilibria, trace element thermometry, bulk composition, heat sources, timescales and tectonic settings

On ultrahigh temperature crustal metamorphism: Phase equilibria, trace element thermometry, bulk composition, heat sources, timescales and tectonic settings

The link between oxygen isotope resetting, partial melting, and fluid flow in metamorphic terrains

Distribution of boron, lithium and beryllium in ocean island basalts from French Polynesia: implications for the B/Be and Li/Be ratios as tracers of subducted components

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