Retrograde contact meta-morphism in the granulite facies terrain of Mont Tremblant Park, Quebec, Canada

1968 ◽  
Vol 105 (5) ◽  
pp. 487-492 ◽  
Author(s):  
Michael B. Katz
Keyword(s):  
Late Stage ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Grenville Province ◽  
South West ◽  
Mineral Assemblages ◽  
Park Area

SUMMARYThe Pre-Cambrian rocks of the Grenville province of south-west Quebec in the Mont Tremblant Park area consists of granulites and associated gneisses formed under granulite facies conditions which are intruded by members of an anorthosite suite. At the contacts of these intrusives especially the late-stage members, the granulites and gneisses were found to be retrograded into rocks with mineral assemblages typical of the amphibolite facies. The transformation of the granulite facies rocks into rocks of lower amphibolite grade can be attributed to local introduction of water which was supplied during the emplacement and crystallization of this late-stage, volatile-enriched magma of the anorthosite suite.

Multi-stage metamorphism of the South Altyn ultrahigh-pressure metamorphic belt, West China: insights into tectonic evolution from continental subduction to arc–backarc extension

2021 ◽  
Author(s):  
Jie Dong ◽  
Chunjing Wei
Keyword(s):  
Late Stage ◽  
Tectonic Evolution ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Ultrahigh Pressure ◽  
Garnet Amphibolite ◽  
The South ◽  
Metamorphic Belt ◽  
Mineral Assemblages ◽  
Eclogite Facies

Abstract The South Altyn ultrahigh-pressure (UHP) metamorphic belt is claimed to host the deepest subducted continental crust based on the discovery of former stishovite, and thus can provide unique insights into the tectonic evolution from deep continental subduction and exhumation to arc–backarc extension. In this paper, we present detailed studies of petrography, mineral chemistry, phase equilibria modelling and zircon U-Pb dating for three representative samples involving garnet amphibolite (A1531 & A1533) and associated garnet-biotite gneiss (A1534) from the UHP belt. Three phases of metamorphism are inferred for the rocks. The first phase high pressure (HP)–UHP-type eclogite facies is represented by the mineral assemblages of garnet and phengite inclusions in zircon and garnet cores with the high grossular (XGrs = 0.33–0.34). The Si contents of 3.40–3.53 and 3.24–3.25 p.f.u. in phengite inclusions yield pressure conditions of >1.7–2.3 GPa for A1533 and 2.5–2.55 GPa for A1534 at a fixed temperature of 770 °C. The second phase medium-pressure (MP)-type overprinting of garnet amphibolite facies shows P–T conditions of 0.8–1.2 GPa/750–785 °C based on the stability fields of corresponding mineral assemblages, the measured isopleths of Ti contents in biotite and amphibole cores, and XGrs in garnet. The third phase low-pressure (LP) type overprinting includes early-stage heating to peak granulite facies followed by cooling towards a late-stage amphibolite facies. The peak granulite facies is represented by the high Ti amphibole mantle, high Zr titanite and the intergrowths of clinopyroxene + ilmenite in A1533 & A1531, with P–T conditions of 800–875 °C/0.80–0.95 GPa. The late-stage is defined by the solidus assemblages, giving P–T conditions of 0.5–0.7 GPa/720–805 °C. U-Pb geochronology on metamorphic zircons from A1533 and A1534 gives three ages of c. 500 Ma, c. 482 Ma and c. 460 Ma. They are interpreted to represent the HP–UHP, MP and LP types of metamorphism respectively, based on cathodoluminescence images, mineral inclusions and trace element patterns. Combining the regional geology and metamorphic evolution from the Altyn Orogen, a tectonic model is inferred, including the following tectonic scenarios. The small Altyn Microcontinent was subducted to great mantle depths with dragging of the surrounding vast oceanic lithosphere to undergo the HP–UHP eclogite facies metamorphism during the early subduction stage (c. 500 Ma) of the Proto-Tethys Ocean. Then, the subducted slabs were exhumed to a thickened crust region to be overprinted by the MP-type assemblages at c. 482 Ma. Finally, an arc–backarc extension was operated within the thickened crust region due to the retreat of subduction zones. It caused evident heating and the LP-type metamorphic overprinting at c. 460 Ma, with a fairly long interval of 30–40 Myr after the HP–UHP metamorphism, distinct from the short interval of <5–10 Myr in the Bohemian Massif.

Progressive metamorphism of pelitic and quartzofeldspathic rocks in the Grenville Province of western Labrador — tectonic implications of bathozone 6 assemblages

1983 ◽  
Vol 20 (12) ◽  
pp. 1791-1804 ◽  
Author(s):  
T. Rivers
Keyword(s):  
Experimental Data ◽  
Pressure Gradient ◽  
Granulite Facies ◽  
Lithostatic Pressure ◽  
Lower Grade ◽  
High Grade ◽  
Tectonic Zone ◽  
Grenville Province ◽  
Mineral Assemblages ◽  
Grenvillian Orogeny

Aphebian metapelites and quartzofeldspathic rocks from the Grenville Province south of the Labrador Trough display progressive changes in mineral assemblages as a result of Grenvillian metamorphism, consistent with variation in grade from greenschist to upper amphibolite facies. The following metamorphic zones have been delineated: (i) chlorite–muscovite; (ii) chlorite–muscovite–biotite; (iii) chlorite–muscovite–biotite–garnet; (iv) muscovite–staurolite–kyanite; (v) muscovite–garnet–biotite–kyanite; (vi) muscovite–garnet–biotite–kyanite–granitic veins; (vii) K–feldspar–kyanite – granitic veins; (viii) K-feldspar–sillimanite–granitic veins. Reactions linking the lower grade metamorphic zones are interpreted to be dehydration phenomena, whilst anatectic reactions occur at higher grades. At lower metamorphic grades aH2O was high [Formula: see text] but it declined progressively as water entered the melt phase during higher grade anatectic reactions. With the onset of vapour-absent anatexis, the restite assemblage became essentially "dry" [Formula: see text], and biotite breakdown occurred in granulite-facies rocks east of the study area. Consideration of available experimental data suggests that metamorphic temperatures ranged from approximately 450 to 750 °C across the study area. Lithostatic pressure during metamorphism reached about 8 kbar (800 MPa) in the high-grade zones, with estimates at lower grades being poorly constrained; however, a steep pressure gradient across the map area is postulated.This is the first reported occurrence of bathozone 6 assemblages from a progressive metamorphic sequence, and it indicates the presence of an unusually great thickness of supracrustal rocks during the Grenvillian Orogeny. This was achieved by imbricate stacking of thrust slices, perhaps doubling the thickness of the crust in the Grenville Front Tectonic Zone, creating a huge gravity anomaly of which a remnant still persists today.

Coeval migmatites and granulites, Muskoka domain, southwestern Grenville Province, Ontario

2002 ◽  
Vol 39 (2) ◽  
pp. 239-258 ◽  
Author(s):  
Hilke Timmermann ◽  
Rebecca A Jamieson ◽  
Randall R Parrish ◽  
Nicholas G Culshaw
Keyword(s):  
Granulite Facies ◽  
Amphibolite Facies ◽  
Geochronological Data ◽  
Grenville Province ◽  
Mafic Enclaves ◽  
High Grade Metamorphism ◽  
Granitoid Gneisses ◽  
Central Gneiss Belt ◽  
The Relationship ◽  
Extensional Structures

We present new field observations and petrologic and geochronological data from the Muskoka domain in the southwestern Grenville Province of Ontario in an attempt to constrain the relationship between amphibolite-facies and granulite-facies gneisses in areas of transitional metamorphic grade, and to examine their implication for tectonometamorphic models for the Grenville Province of Ontario. The predominant medium-grained amphibolite-facies migmatitic orthogneisses of the Muskoka domain contain several generations of leucosome, some of which are related to southeast-directed extensional structures. The amphibolite-facies granitoid gneisses contain numerous mafic enclaves with granulite-facies assemblages recrystallized from anhydrous precursors during Grenvillian metamorphism. Other associated granulites are characterized by their patchy occurrence and gradational contacts, similar to the charnockites in southern India. Patchy granulites, leucocratic vein networks in mafic enclaves, and crosscutting leucocratic granulite veins are interpreted to have formed as a result of local differences in reaction sequences and (or) fluid compositions. The U–Pb zircon lower intercept age of the patchy granulites overlaps with the previously determined range of 1080–1060 Ma for high-grade metamorphism in the Muskoka domain, while zircon and titanite from a crosscutting granulite vein crystallized at about 1065–1045 Ma, supporting a Grenvillian age for granulite formation. Peak metamorphic conditions of 750–850°C and 10–11.5 kbar (1 kbar = 100 MPa) were determined from the mafic enclaves, whereas the more felsic migmatites reequilibrated at somewhat lower temperatures. The high temperatures caused extensive migmatization and facilitated rheological weakening of the Muskoka domain 10–25 million years after the start of the Ottawan orogeny in the Central Gneiss Belt.

Resetting of Nd and Sr whole-rock isochrons from polymetamorphic granulites, northeastern Alberta

1985 ◽  
Vol 22 (7) ◽  
pp. 992-1000 ◽  
Author(s):  
R. A. Burwash ◽  
J. Krupicka ◽  
A. R. Basu ◽  
P. A. Wagner
Keyword(s):  
Regional Scale ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Lower Pressure ◽  
Mafic Rocks ◽  
Isotopic System ◽  
Mineral Assemblages ◽  
The Times ◽  
Northeastern Alberta

At Mountain Rapids on the Slave River, mafic xenoliths are enclosed by a granodiorite host, which is, in turn, surrounded by a granitic migmatite complex. The mafic and granodioritic rocks are both metamorphosed to the hornblende granulite facies, and the migmatite has been metamorphosed to the upper amphibolite facies. The banding of the mafic granulites is truncated by sharply defined boundaries with the felsic granulites. The felsic granulites contain K-feldspar, the mafic rocks almost none. The mineral assemblages are otherwise identical: plagioclase–hypersthene–quartz–biotite–magnetite.A whole-rock Sm–Nd isochron of one felsic and six mafic granulites gives 2436 ± 44 Ma [Formula: see text]. This time is significantly younger than the Sm–Nd model ages. The same mafic samples give a Rb–Sr age of 1898 ± 5 Ma. These are interpreted as the times of reequilibration and closure of the Rb–Sr isotopic systems within the Mountain Rapids Granulite enclave. From cordierite–garnet barometry the indicated pressure of the younger event is 5.5 ± 0.7 kbar (550 ± 70 MPa). By analogy with hornblende granulite assemblages elsewhere, the older event probably occurred in the intermediate crust (~25–30 km depth). This event apparently effectively reset the Sm–Nd isotopic system; subsequent cooling closed it. Once established this system withstood the later, lower pressure event that reset the Rb–Sr geochronometer on a regional scale.

The Tremolite Isograd near Marble Lake, Ontario

1973 ◽  
Vol 10 (6) ◽  
pp. 936-947 ◽  
Author(s):  
Ian Hutcheon ◽  
J. M. Moore
Keyword(s):  
Vapor Phase ◽  
Experimental Work ◽  
Lake Ontario ◽  
Amphibolite Facies ◽  
High Angle ◽  
Grenville Province ◽  
Metavolcanic Rocks ◽  
Mineral Assemblages ◽  
Total P

Marble, metavolcanic rocks, and pelite are found in a northeasterly trending belt near Marble Lake, in the Grenville Province, Ontario. The rocks have been metamorphosed to the lower amphibolite facies in the southwest, the grade increasing to the mid-amphibolite facies towards the northeast. Northwest-trending isograds in the metavolcanic rocks are at a high angle to the northeast-trending tremolite isograd in the marbles. Mineral assemblages indicate total pressures between 4 and 5 kbar and temperatures ranging from approximately 350 °C to over 600 °C. Temperatures estimated by calcite–dolomite solvus geothermometry and applied to experimental work in the system CaO–MgO–SiO2–CO2–H2O indicate: (i) P(total) = P(CO2) + P(H2O) was greater than 3 kbars; (ii) temperatures on the tremolite isograd were from approximately 450 to 550 °C and indicate that the tremolite isograd is not isothermal; (iii) the composition of the vapor phase present during metamorphism was approximately X(CO2) = 0.7 – 0.8; (iv) temperatures in the belt were from less than 400 °C in the southwest to more than 600 °C in the northeast.

Proterozoic metamorphism in the Grenville Province: a study in the Double Mer – Lake Melville area, eastern Labrador

1988 ◽  
Vol 25 (11) ◽  
pp. 1895-1905 ◽  
Author(s):  
C. F. Gower ◽  
P. Erdmer
Keyword(s):  
Granulite Facies ◽  
High Grade ◽  
Structural Configuration ◽  
Geochronological Data ◽  
Granitic Gneiss ◽  
Grenville Province ◽  
Accessory Minerals ◽  
Mineral Assemblages ◽  
Host Rocks ◽  
Metamorphic Gradient

A regional metamorphic gradient from upper greenschist to granulite facies is identified south of the Grenville front in the Double Mer – Lake Melville area of eastern Labrador. Mineral assemblages in politic–granitic gneiss, amphibole-bearing quartzo-feldspathic gneiss, and coronitic metagabbro allow three major metamorphic domains to be established. These are collectively divisible into 11 subdomains. Geothermobarometry applied to the higher grade domains suggests that each is characterized by specific P–T conditions, which achieved 1000–1100 MPa and 700–800 °C in the deepest level rocks.The problem of reconciling geochronological data (which record a major orogenic event at 1650 Ma) with the occurrence of high-grade mineral assemblages in 1426 Ma metagabbro (which suggests a pervasive Grenvillian event) is discussed in terms of three models. The preferred model envisages crustal stabilization at 1650–1600 Ma to give high-grade mineral assemblages seen in the host rocks and with which mineral assemblages in coronitic metagabbro equilibrated after their emplacement at 1426 Ma. During Grenvillian orogenesis (1080–920 Ma) the present structural configuration was achieved by thrust stacking. This imparted a sporadic metamorphic and structural overprint and Grenvillian ages in selected accessory minerals.

Hydrothermally altered volcanic rocks metamorphosed at granulite-facies conditions: an example from the Grenville Province

2017 ◽  
Vol 54 (6) ◽  
pp. 622-638 ◽  
Author(s):  
Marisa Hindemith ◽  
Aphrodite Indares ◽  
Stephen Piercey
Keyword(s):  
Hydrothermal Alteration ◽  
Volcanic Rocks ◽  
Granulite Facies ◽  
Metamorphic Overprint ◽  
Grenville Province ◽  
Rock Types ◽  
Argillic Alteration ◽  
New Findings ◽  
Mineral Assemblages ◽  
Liberation Analysis

A 1.2 Ga association of aluminous gneisses, garnetites, and white felsic gneisses of andesitic composition in the southern Manicouagan area (central Grenville Province) provides evidence consistent with protolith formation and hydrothermal alteration in a submarine volcanic environment. In addition to field relations, potential relics of quartz phenocrysts in the aluminous gneisses, revealed by SEM–MLA (scanning electron microscope with a mineral liberation analysis software) imaging, are consistent with a volcanic precursor. Moreover, in these rocks, aluminous nodules and seams of sillimanite are considered to represent metamorphosed hydrothermal mineral assemblages and to reflect former pathways of hydrothermal fluid. These features are preserved despite the Grenvillian granulite-facies metamorphic overprint and evidence of partial melting. In addition, the garnetites are inferred to represent hydrothermally altered products of the white gneisses, based on the gradational contacts between the two rock types. The compositional ranges of minerals are generally similar to those of granulite-facies metapelites, but moderately elevated contents of Mn in garnet from the garnetites, and Zn in spinel from the aluminous gneisses, are consistent with hydrothermal addition of these elements to the protolith. The most prominent alteration trends are an increase in Fe–Mg–Mn from the white gneisses to the aluminous gneisses and the garnetites, and a trend of increasing alumina index in some white gneisses, suggesting mild argillic alteration. The new findings highlight the preservation of early hydrothermal alteration in high-grade metamorphic belts in the Grenville Province, and these altered rocks are potential targets for exploration.

Delineation of isograds in siliceous dolomitic marbles along the Sharbot Lake – Frontenac terrane boundary of the Grenville Province, southeastern Ontario

2008 ◽  
Vol 45 (6) ◽  
pp. 669-691
Author(s):  
Jo-Anne S. Goodwin-Bell
Keyword(s):  
Field Gradient ◽  
Amphibolite Facies ◽  
Petrographic Analysis ◽  
Fluid Composition ◽  
Grenville Province ◽  
Mineral Assemblages ◽  
Facies Metamorphism ◽  
Uniform Composition

This study presents details of the mineralogy and petrology of siliceous, dolomitic marbles of the Sharbot Lake domain along the Frontenac terrane boundary in the Grenville Province of southeastern Ontario. The location of four mineral isograds in the marble and the related univariant reactions were identified in the Almonte – Carleton Place area. Delineation of the isograds is based on detailed mapping, petrographic analysis of coexisting mineral assemblages, and a polybaric T–XCO2 diagram calculated using thermobarometric data from associated gneissic rocks, where T is temperature and X is fluid composition. The T–X section is based on a field gradient of 32 °C/km. The isograds correspond to the first appearance of tremolite (5 dolomite + 8 quartz + H2O = tremolite + 3 calcite + 7 CO2), diopside (tremolite + 3 calcite + 2 quartz = 5 diopside + 3 CO2 + H2O), diopside + dolomite (tremolite + 3 calcite = dolomite + 4 diopside + H2O + CO2), and forsterite (diopside + 3 dolomite = 2 forsterite + 4 calcite + 5 CO2). Mineral assemblages above and below each isograd are described and relevant examples are shown. Results of this study are consistent with a mixed volatile fluid of a uniform composition during mid- to upper amphibolite-facies metamorphism.

Polymetamorphism of marbles in the Morin terrane, Grenville Province, Quebec

2005 ◽  
Vol 42 (10) ◽  
pp. 1949-1965 ◽  
Author(s):  
William H Peck ◽  
Michael T DeAngelis ◽  
Michael T Meredith ◽  
Etienne Morin
Keyword(s):  
Shear Zones ◽  
Granulite Facies ◽  
Grenville Province ◽  
Anorthosite Massif ◽  
Mineral Assemblages ◽  
Intrusive Rocks ◽  
Granitic Intrusions ◽  
T Path ◽  
The Village

The Morin terrane (Grenville Province, Quebec) is dominated by the 1.15 Ga Morin Anorthosite Massif and related granitic intrusions, all of which exhibit granulite-facies mineral assemblages. Anorthosite-suite rocks are deformed both in shear zones and in the interior of the terrane and show intrusive contact relations with marble along road cuts near the village of St. Jovite. Intrusive rocks exposed in these road cuts have well-developed skarns, which were deformed with the intrusions after emplacement. Skarn minerals are consumed by garnet-forming reactions (e.g., An + Wo = Gr + Qtz) that preserve granulite-facies temperatures and pressures. Calcite–graphite thermometry of Morin terrane marbles records temperatures of 755 ± 38 °C (n = 21), independent of proximity to anorthosite-suite plutons. Preserved metamorphic conditions and the retrograde pressure–temperature (P–T) path in the Morin terrane are very similar to conditions during the 1.07 Ga Ottawan orogeny in the Adirondack Highlands. Metamorphism and deformation of anorthosite-suite rocks and marbles of the Morin terrane are consistent with anorthosite intrusion followed by a distinct granulite-facies overprint.

scholarly journals The geology and petrology of the Precambrian rocks to the north-east of the fjord Qagssit, Frederikshåb district, South-West Greenland

1972 ◽  
Vol 103 ◽  
pp. 1-98
Author(s):  
G Rivalenti ◽  
A Rossi
Keyword(s):  
Granulite Facies ◽  
Amphibolite Facies ◽  
Ductile Deformation ◽  
Brittle Deformation ◽  
Metamorphic History ◽  
North East ◽  
The North ◽  
South West ◽  
Five Phases ◽  
The Relationship

The area consists of migmatitic gneisses (with related pegmatites) containing small inclusions and larger concordant layers of unmigmatised rocks (mainly represented by amphibolites, metasediments and ultramafics), and a few discordant amphibolite dykes. The petrography of the various lithotypes is described and their petrogenesis discussed. The following metamorphic history is proposed: 1) an increase in metamorphic grade to the biotite-almandine-cordierite subfacies of the low hornblende-granuIite facies, shown only by a few relic assemblages, followed by 2) retrogression to within the almandine-amphibolite facies. Migmatisation (quartz dioritisation or granodioritisation) started in the low hornblende-granulite facies and reached its maximum in the upper almandine-amphiboIite facies. A general microcline blastesis and formation of microcline-rich mobilisates is ascribed to the medium to low almandine-amphibolite facies. Further retrogression to epidoteamphiboIite or greenschist facies is only local and weak. Several generations of post-orogenic basic dykes intersect the gneisses. Structurally, five phases of ductile deformation and three phases of brittle deformation are distinguished, and the relationship between deformation and metamorphism tentatively established. The metamorphic and structural events are mostly pre-Ketilidian.

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