Iron-titanium oxides as an indicator of the role of the fluid phase during the cooling of granites metamorphosed to granulite grade

1980 ◽  
Vol 43 (329) ◽  
pp. 623-631 ◽  
Author(s):  
Hugh R. Rollinson
Keyword(s):  
Fluid Phase ◽  
Granulite Facies ◽  
Granitic Rocks ◽  
Titanium Oxides ◽  
Cooling History ◽  
Granulite Facies Metamorphism ◽  
North West ◽  
Facies Metamorphism ◽  
History Of

SummaryA detailed electron probe study of irontitanium oxide intergrowths from slowly cooled granitic rocks from the granulite grade, Archaean Scourian complex of north-west Scotland has yielded a wealth of information about magmatic and metamorphic temperatures, subsolidus cooling, and the behaviour of the fluid phase during cooling. Five stages are documented in the cooling history of granites and trondhjemites which include: (i) magmatic-subsolidus cooling (1035 °C–890 °C); (ii) granulite facies metamorphism and the accompanied expulsion of a hydrous fluid phase (890 °C–830 °C); (iii) subsolidus cooling following the peak of the granulite facies metamorphism (830 °C–660 °C); (iv) the localized reintroduction of water into the rocks during retrogression (660 °C–530 °C) and (v) subsolidus cooling and re-equilibration in the presence of a finite amount of H2O (530 °C–320 °C).

Silicate, Oxide and Sulphide Trends in Neo-Archean Rocks from the Nilgiri Block, Southern India: the Role of Fluids During High-grade Metamorphism

2019 ◽  
Vol 60 (5) ◽  
pp. 1027-1062 ◽  
Author(s):  
Vinod O Samuel ◽  
Daniel E Harlov ◽  
Sanghoon Kwon ◽  
K Sajeev
Keyword(s):  
Granulite Facies ◽  
Southern India ◽  
Sulphide Mineral ◽  
High Grade ◽  
Regional Trend ◽  
Granulite Facies Metamorphism ◽  
Facies Metamorphism ◽  
High Grade Metamorphism ◽  
Specific Oxidation

Abstract The Nilgiri Block, southern India represents an exhumed section of lower, late Archean (2500 Ma) crust. The northern highlands of the Nilgiri Block are characterized by metagabbros with pyroxenite inlayers. A two-pyroxene granulite zone acts as a transition between the metagabbros and charnockites, which are exposed in the central and southern part of the Nilgiri highlands. Thermobarometry results indicate a SW–NE regional trend both in temperature (∼650–800°C) and in pressure (700–1100 MPa) over the Nilgiri highlands. In the charnockites, composite rutile–ilmenite grains are the dominant oxide assemblage. In the two-pyroxene granulites, hemo-ilmenite–magnetite is dominant with coexisting rutile–ilmenite composite grains in a few samples in the vicinity of the boundary with the charnockites. In the metagabbros, hemo-ilmenite–magnetite is the dominant oxide assemblage. The principal sulphide mineral in the charnockite is pyrrhotite with minor pyrite–chalcopyrite exsolution lamellae or blebs. In the two-pyroxene granulites and the metagabbros, the principal sulphide assemblage consists of discrete pyrite grains with magnetite rims and pyrite–pyrrhotite–chalcocopyrite associations. From these observations, a specific oxidation trend is seen. The northern granulite-facies metagabbros and two-pyroxene granulites of the Nilgiri highlands are highly oxidized compared with the charnockites from the central and southern regions. This higher oxidation state is proposed to be the result of highly oxidizing agents (probably as SO3) in low H2O activity grain boundary NaCl saline fluids with a dissolved CaSO4 component present during granulite-facies metamorphism of the metagabbros and two-pyroxene granulites. Eventually these agents became more reducing, owing to the inherent buffering of the original tonalite–granodiorite granitoids at the graphite–CO2 buffer, such that S took the form of H2S during the granulite-facies metamorphism of the charnockites. At the same time, these saline fluids were also responsible the solid-state conversion of biotite and amphibole to orthopyroxene and clinopyroxene in the metagabbro, two-pyroxene granulite, and charnockite.

Granulite Facies Metamorphism in the Coast Range Crystalline Belt

1975 ◽  
Vol 12 (11) ◽  
pp. 1953-1955 ◽  
Author(s):  
Lincoln S. Hollister
Keyword(s):  
British Columbia ◽  
Granulite Facies ◽  
Coast Range ◽  
Geologic History ◽  
Granulite Facies Metamorphism ◽  
Mineral Assemblages ◽  
Facies Metamorphism ◽  
History Of

Mineral assemblages diagnostic of the granulite facies of metamorphism occur between Terrace and Prince Rupert, British Columbia. The estimated pressure (5–8 kb) and temperature (750–850 °C) of metamorphism are important constraints in unravelling the geologic history of the Coast Range batholithic complex.

Tectonic history of the Grenville-age Trenton Prong inlier, Central Appalachians, USA: Evidence from SHRIMP U–Pb geochronology

2021 ◽  
Author(s):  
Richard Volkert ◽  
John N. Aleinikoff
Keyword(s):  
Granulite Facies ◽  
Small Population ◽  
Local Source ◽  
Thermal Activity ◽  
Granulite Facies Metamorphism ◽  
Magmatic Arc ◽  
Tectonic History ◽  
Facies Metamorphism ◽  
Minimum Age ◽  
History Of

New zircon U–Pb geochronologic data from the Grenville-age Trenton Prong provide information on the age of magmatism, timing of metamorphism, and post-metamorphic history of the inlier. Diorite gneiss (1318 ± 13 Ma) of the Colonial Lake Suite temporally correlates to magmatic arc sequences that formed along the eastern margin of Laurentia at <1.4 Ga. Metasedimentary gneisses yielded detrital zircon ages of ca. 1319-1133 Ma and ca. 1370-1207, consistent with sediment derived from a similar local source of Laurentian affinity. A small population of zircon (either detrital or igneous in origin) in one sample yielded ages of ca. 1074-1037 Ma. Possible interpretations for their formation are explored. Ca. 1060 Ma overgrowths on zircon in the northern part of the inlier constrain the timing of granulite-facies metamorphism to the Ottawan phase of the Grenvillian Orogeny. The undeformed Assunpink Creek Granite (1041 ± 6 Ma) intruded country rocks as small bodies of late-orogenic syenogranite. It provides a minimum age for amphibolite-facies metamorphism and Ottawan orogenesis elsewhere in the inlier. Regionally, zircon rim ages of ca. 1010–960 Ma record continued thermal activity during the Rigolet phase of the orogen that resulted in migmatization of paragneiss at ca. 1004 Ma and juxtaposition of upper- and mid-crustal rocks during orogenic collapse. The lithologic ages and tectonic history of the Trenton Prong correlate to those in other Appalachian Mesoproterozoic inliers, and parts of the Canadian Grenville Province, confirming it is not an exotic terrane that was accreted to eastern Laurentia during Grenvillian orogenesis.

scholarly journals Metasomatic Reactions between Archean Dunite and Trondhjemite at the Seqi Olivine Mine in Greenland

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 85 ◽  
Author(s):  
Laura Whyatt ◽  
Stefan Peters ◽  
Andreas Pack ◽  
Christopher L. Kirkland ◽  
Tonci Balic-Zunic ◽  
...  
Keyword(s):  
Isotope Analysis ◽  
Fluid Phase ◽  
Granulite Facies ◽  
Zircon Crystal ◽  
Compositional Gradient ◽  
Granulite Facies Metamorphism ◽  
Icp Ms ◽  
Ultramafic Complex ◽  
Facies Metamorphism

A metasomatic zone formed between the contact of a 2940 ± 5 Ma intrusive trondhjemite sheet in the Archean dunite of the Seqi Ultramafic Complex, SW Greenland, consists of three distinct mineral zones dominated by (1) talc, (2) anthophyllite, and (3) phlogopite. These zones supposedly resulted from a process of dissolution of olivine by silica rich fluid residual from the trondhjemite magma, with crystallization of secondary minerals along a compositional gradient in the fluid phase. A zircon crystal inclusion in a large (4 cm) olivine porphyroblast was dated in situ via LA-ICP-MS U–Pb isotope analysis, yielding a weighted mean 207Pb/206Pb age of 2963 ± 1 Ma, which coincides with granulite facies metamorphism and potential dehydration. Considering phase relations appropriate for the dunite composition, we deduced the talc forming conditions to be at temperatures of 600–650 °C and at a pressure below 1 GPa. This is supported by oxygen isotope data for talc, anthophyllite and phlogopite in the metasomatic zone, which suggests formation in the temperature range of 600–700 °C from fluids that had a δ18O of ~8‰ and a Δ’17O0.528 of about −40 ppm, i.e., from fluids that could have been derived from the late stage trondhjemite sheet.

Regional geothermobarometry in the granulite facies terrane of South India

1983 ◽  
Vol 73 (4) ◽  
pp. 221-244 ◽  
Author(s):  
M. Raith ◽  
P. Raase ◽  
D. Ackermand ◽  
R. K. Lal
Keyword(s):  
South India ◽  
Analytical Data ◽  
Granulite Facies ◽  
Critical Discussion ◽  
Granulite Facies Metamorphism ◽  
Northern Margin ◽  
Mineral Equilibria ◽  
Metamorphic History ◽  
Facies Metamorphism ◽  
History Of

ABSTRACTIn the southern part of the Archaean craton of South India, an approximately 3.4–2.9 b.y. old migmatite–gneiss terrane (Peninsular gneiss complex) has been subjected to granulite facies metamorphism about 2.6 b.y. ago. During this event, the extensive charnockite-khondalite zone of southern India developed. A younger metamorphism (Proterozoic?) led to retrogression of the charnockites and khondalites, mainly under the conditions of the amphibolite facies.The physical conditions of metamorphism have been evaluated by applying methods of geothermobarometry to the widespread charnockitic assemblages with garnet, orthopyroxene, clinopyroxene, plagioclase, and quartz. The interpretation of the P–T estimates includes a critical discussion of potential error sources, e.g. errors of the analytical data and the calibrations of the models, and takes into account the complex metamorphic history of the rocks and the kinetics of the mineral equilibria.P-T estimates were obtained for seven subareas from the rim compositions of the coexisting minerals: Shevaroy Hills 680±55°C—7·4±1 kb; Kollaimalai area 680±40°C—8·6± 1 kb; Nilgiri Hills 680±90°C—6·6±0.8kb (upland massif) and 705±60°C—9·3±0.8 kb (northern margin); Bhavani Sagar area 650±50°C—7·2± 1 kb; Sargur-Mysore area 690±60°C—7·6 kb; Bangalore-Kunigal-Satnur area 760±50°C—6 kb. Except for the last subarea, the P-T model data reflect the conditions of a late annealing stage probably related to the retrogressive metamorphism. Conditions near the peak of granulite facies metamorphism (730–800°C—6·5–9·5 kb) are recorded by the core compositions of the minerals. Although a rather uniform cooling history of the main part of the charnockite-khondalite terrane is suggested from the temperature data, differential uplift of smaller blocks is indicated by the regional variation of the pressure data.

scholarly journals Fluid-induced metamorphism and anatexis of refractory Ni-Co-Cu sulphides in subduction-related rocks

2019 ◽  
Vol 98 ◽  
pp. 08008
Author(s):  
Nikita Kepezhinskas
Keyword(s):  
Granulite Facies ◽  
High Grade ◽  
Accretionary Complex ◽  
Sulfide Mineralization ◽  
Granulite Facies Metamorphism ◽  
Grade Metamorphism ◽  
Facies Metamorphism ◽  
High Grade Metamorphism ◽  
Bay Islands

The role of metamorphism on refractory sulfides is not well constrained. Although experiments have displayed the effectiveness of high grade metamorphism, namely granulite facies metamorphism, on sulfide anatexis, its role in the presence of other variables is still poorly understood. Rocks from the Bay Islands Accretionary Complex in Honduras and the Ildeus-Lucha Complex in Russia exhibit extensive metamorphism. Sulfide mineralization is prolific in these rocks suggesting that metamorphism has played an important role in re-concentrating these sulfides during amphibolite and granulite facies metamorphism.

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