scholarly journals Constraints from Geochemistry and Field Relationships for the Origin of Kornerupine-Bearing Gneiss from the Grenvillian New Jersey Highlands and Implications for the Source of Boron

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 431 ◽  
Author(s):  
Richard A. Volkert
Keyword(s):  
New Jersey ◽  
Granulite Facies ◽  
Sediment Source ◽  
Prograde Metamorphism ◽  
Ti Oxides ◽  
Dehydration Reactions ◽  
Grenvillian Orogeny

Kornerupine ± prismatine is present in granulite-facies paragneiss at two locations in the Grenvillian New Jersey Highlands, occurring in an assemblage composed of quartz + biotite + K-feldspar + plagioclase + garnet + Fe-Ti oxides ± sillimanite ± rutile ± graphite. Estimates of the metamorphic conditions of the host gneiss are ≥600 MPa and ~740 °C during the Ottawan phase of the Grenvillian Orogeny. Geochemical compositions of kornerupine-bearing gneiss are consistent with protoliths that were graywacke sandstone and pelite. Metagraywacke is characterized by (in wt. %) 62–76% SiO2, 0.3–0.8% TiO2, 13–16% Al2O3, 0.6–4.3% CaO, 2.2–6.4% Na2O, 1.7–7.4% K2O, and 90–260 ppm Zr; metapelite has lower SiO2 (53–66%) and CaO (0.5–2.0%), higher TiO2 (0.9–1.8%), Al2O3, (15–26%), and Zr (210–490 ppm), and comparable Na2O (2.5–4.9%) and K2O (2.5–7.4%). Indices of weathering and alteration yield low to intermediate values implying a relatively unweathered sediment source. Provenance discriminants suggest the protoliths formed from immature, first-cycle sediments derived mainly from a felsic arc-related source. The geological relationships of kornerupine-bearing gneiss are most compatible with boron sourced from B-rich sediments deposited in the protoliths between ca. 1299 and 1238 Ma. The breakdown of these sediments due to dehydration reactions during Ottawan prograde metamorphism led to mobilization of a B-rich fluid that migrated short distances to favorable structural sites in the host gneiss, resulting in precipitation of the borosilicates.

A Discussion on global tectonics in Proterozoic times - The Grenville Province in Helikian times: a possible model of evolution

1976 ◽  
Vol 280 (1298) ◽  
pp. 499-515 ◽  
Keyword(s):  
Continental Crust ◽  
Granulite Facies ◽  
Continental Collision ◽  
Canadian Shield ◽  
Grenville Province ◽  
East Central ◽  
Metasedimentary Rocks ◽  
Grenvillian Orogeny ◽  
Triangular Area ◽  
Global Tectonics

It is suggested that the Helikian (1650-1000 million years (Ma) ago) evolution of the Grenville Province in the Canadian Shield was marked by three events: emplacement of anorthosites around 1450-1500 Ma ago, rifting associated with opening of a proto-Atlantic ocean between 1200 and 1300 Ma ago, and continental collision responsible for the Grenvillian ‘orogeny’ about 1100-1000 Ma ago. Emplacement of rocks of the anorthosite suite (anorthosites and adamellites or mangerites) into continental crust was accompanied by formation of aureoles in the granulite facies. The Grenville Group was deposited in the southern part of the Province between 1300 and 1200 Ma ago and comprises marbles, clastic metasedimentary rocks and volcanics. It occupies a roughly triangular area limited on the northwest by the Bancroft—Renfrew lineament and on the southeast by the Chibougamau—Gatineau lineament. It is thought to have been accumulated in an aulacogen that would have developed along a fracture zone separating two basement blocks. The Grenvillian thermotectonic event may represent a Tibetan continental collision in the sense of Burke & Dewey. The suture zone would now be hidden under the Appalachians. Collision would cause reactivation of continental crust and renewed movement on pre-existing lineaments. The east—central part of the Grenville Province appears to have been more intensively reactivated than the western part.

Mafic and ultrapotassic rocks from the Canyon domain (central Grenville Province): geochemistry and tectonic implications

2012 ◽  
Vol 49 (2) ◽  
pp. 412-433 ◽  
Author(s):  
Carolina Valverde Cardenas ◽  
Aphrodite Indares ◽  
George Jenner
Keyword(s):  
Tectonic Setting ◽  
Source Region ◽  
Crustal Contamination ◽  
Granulite Facies ◽  
Grenville Province ◽  
Mafic Rocks ◽  
Isotopic Signatures ◽  
Late Evolution ◽  
Grenvillian Orogeny ◽  
Laurentian Margin

The Canyon domain and the Banded complex in the Manicouagan area of the Grenville Province preserve a record of magmatic activity from ∼1.4 to 1 Ga. This study focuses on 1.4–1.2 Ga mafic rocks and 1 Ga ultrapotassic dykes. Geochemistry and Sm–Nd isotopic signatures were used to constrain the origin of these rocks and evaluate the changing role of the mantle with time and tectonic setting from the late evolution of the Laurentian margin to the Grenvillian orogeny, in the Manicouagan area. The mafic rocks include layers inferred to represent flows, homogeneous bodies in mafic migmatite, and deformed dykes, all of which were recrystallized under granulite-facies conditions during the Grenvillian orogeny. In spite of the complexities inherent in these deformed and metamorphosed mafic rocks, we were able to recognize suites with distinctive geochemical and isotopic signatures. Integration of this data along with available ages is consistent with a 1.4 Ga continental arc cut by 1.2 Ga non-arc basalts derived from depleted asthenospheric mantle, with varied degrees of crustal contamination and inferred to represent magmatism in an extensional environment. The 1 Ga ultrapotassic dykes postdate the Grenvillian metamorphism. They are extremely enriched in incompatible elements, have negative Nb anomalies, relatively unradiogenic Sr-isotopic compositions (initial 87Sr/86Sr ~ 0.7040) and εNd –3 to –15. Some dykes have compositional characteristics consistent with derivation from the mantle, ruling out crustal contamination as a major process in their petrogenesis. The most likely source region for the ultrapotassic dykes is a metasomatized subcontinental lithospheric mantle, with thermal input from the asthenosphere in association with post-orogenic delamination.

scholarly journals Interpretation of zircon coronae textures from metapelitic granulites of the Ivrea–Verbano Zone, northern Italy: two-stage decomposition of Fe–Ti oxides

Solid Earth ◽  
2017 ◽  
Vol 8 (4) ◽  
pp. 789-804 ◽  
Author(s):  
Elizaveta Kovaleva ◽  
Håkon O. Austrheim ◽  
Urs S. Klötzli
Keyword(s):  
Host Rock ◽  
Granulite Facies ◽  
Northern Italy ◽  
Retrograde Metamorphism ◽  
Brittle Deformation ◽  
Granulite Facies Metamorphism ◽  
Fine Grained ◽  
Ti Oxides ◽  
Facies Metamorphism ◽  
Metapelitic Granulites

Abstract. In this study, we report the occurrence of zircon coronae textures in metapelitic granulites of the Ivrea–Verbano Zone. Unusual zircon textures are spatially associated with Fe–Ti oxides and occur as (1) vermicular-shaped aggregates 50–200 µm long and 5–20 µm thick and as (2) zircon coronae and fine-grained chains, hundreds of micrometers long and ≤ 1 µm thick, spatially associated with the larger zircon grains. Formation of such textures is a result of zircon precipitation during cooling after peak metamorphic conditions, which involved: (1) decomposition of Zr-rich ilmenite to Zr-bearing rutile, and formation of the vermicular-shaped zircon during retrograde metamorphism and hydration; and (2) recrystallization of Zr-bearing rutile to Zr-depleted rutile intergrown with quartz, and precipitation of the submicron-thick zircon coronae during further exhumation and cooling. We also observed hat-shaped grains that are composed of preexisting zircon overgrown by zircon coronae during stage (2). Formation of vermicular zircon (1) preceded ductile and brittle deformation of the host rock, as vermicular zircon is found both plastically and cataclastically deformed. Formation of thin zircon coronae (2) was coeval with, or immediately after, brittle deformation as coronae are found to fill fractures in the host rock. The latter is evidence of local, fluid-aided mobility of Zr. This study demonstrates that metamorphic zircon can nucleate and grow as a result of hydration reactions and mineral breakdown during cooling after granulite-facies metamorphism. Zircon coronae textures indicate metamorphic reactions in the host rock and establish the direction of the reaction front.

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.

Mesoproterozoic graphite deposits, New Jersey Highlands: geologic and stable isotopic evidence for possible algal origins

2000 ◽  
Vol 37 (12) ◽  
pp. 1665-1675 ◽  
Author(s):  
Richard A Volkert ◽  
Craig A Johnson ◽  
Albert V Tamashausky
Keyword(s):  
New Jersey ◽  
Country Rock ◽  
Sedimentary Environment ◽  
Granulite Facies ◽  
Granulite Facies Metamorphism ◽  
Stable Isotopic ◽  
Facies Metamorphism ◽  
Anoxic Basin ◽  
C Value ◽  
Host Rocks

Graphite deposits of Mesoproterozoic age are locally abundant in the eastern New Jersey Highlands, where they are hosted by sulphidic biotite–quartz–feldspar gneiss, metaquartzite, and anatectic pegmatite. Gneiss and metaquartzite represent a shallow marine shelf sequence of locally organic-rich sand and mud. Graphite from massive deposits within metaquartzite yielded δ13C values of –26 ± 2‰ (1σ), and graphite from massive deposits within biotite-quartz-feldspar gneiss yielded δ13C values of –23 ± 4‰. Disseminated graphite from biotite–quartz–feldspar gneiss country rock was –22 ± 3‰, indistinguishable from the massive deposits hosted by the same lithology. Anatectic pegmatite is graphitic only where generated from graphite-bearing host rocks; one sample gave a δ13C value of –15‰. The δ34S values of trace pyrrhotite are uniform within individual deposits, but vary from 0 to 9‰ from one deposit to another. Apart from pegmatitic occurrences, evidence is lacking for long-range mobilization of carbon during Grenvillian orogenesis or post-Grenvillian tectonism. The field, petrographic, and isotope data suggest that massive graphite was formed by granulite-facies metamorphism of Proterozoic accumulations of sedimentary organic matter, possibly algal mats. Preservation of these accumulations in the sedimentary environment requires anoxic basin waters or rapid burial. Anoxia would also favour the accumulation of dissolved ferrous iron in basin waters, which may explain some of the metasediment-hosted massive magnetite deposits in the New Jersey Highlands.

Metamorphism of the pelitic rocks of the Snyder Group in the contact aureole of the Kiglapait layered intrusion, Labrador: effects of buffering partial pressures of water

1982 ◽  
Vol 19 (10) ◽  
pp. 1888-1909 ◽  
Author(s):  
J. Alexander Speer
Keyword(s):  
Layered Intrusion ◽  
Granulite Facies ◽  
Metamorphic Grade ◽  
Contact Metamorphism ◽  
Contact Aureole ◽  
Partial Pressures ◽  
Dehydration Reactions ◽  
Mineral Assemblages ◽  
Temperature Ranges ◽  
Pelitic Rocks

The petrography and mineral chemistries of the Aphebian Snyder Group pelitic rocks in the contact aureole of the Kiglapait layered intrusion, Labrador reveal a rapid increase in metamorphic grade over 1.7 km from the greenschist facies to the granulite facies. Three zones of metamorphic grade are defined by the aluminum silicates: I, andalusite; II, andalusite + sillimanite; and III, sillimanite. In addition to the succession in the aluminum silicates, progressive metamorphic mineral assemblages, with quartz, K-feldspar, and plagioclase, evolve from chlorite + biotite + muscovite through cordierite + biotite ± muscovite and garnet + cordierite + biotite to orthopyroxene + garnet + cordierite + biotite and eventually either orthopyroxene + cordierite ± biotite or orthopyroxene + garnet + cordierite. Anatectites, believed to be derived from pelitic rocks, intrude as small stocks in zone III. They comprise biotite + cordierite ± garnet ± orthopyroxene monzogranites or granodiorites with accessory ilmenite, rutile, monazite, and dumortierite.The contact metamorphism is isobaric with pressure just above the intersection of the muscovite + quartz decomposition with the andalusite–sillimanite transition. Most published geobarometers place the estimated pressure of metamorphism at 4 ± 1 kbar (400 ± 100 MPa), but use of the lower Holdaway triple point would put it at 2.25 kbar (225 MPa). The temperature ranges from 450 °C in zone I to 900 °C or more adjacent to the Kiglapait intrusion. The range of values of [Formula: see text] is estimated to be 0.1–0.9Ptotal. Because most reactions are dehydration reactions, conditions of [Formula: see text] less than Ptotal allow the metamorphic reactions to buffer the partial pressure of water. This results in the common occurrence of low-variance assemblages and leads to an apparent overlapping of mineral assemblages and mineral chemistries with increasing metamorphic grade.

Geon 12 crustal extension in the central Grenville Province, implications for the orogenic architecture, and potential influence on the emplacement of anorthosites

2013 ◽  
Vol 50 (9) ◽  
pp. 955-966 ◽  
Author(s):  
Aphrodite Indares ◽  
Abdelali Moukhsil
Keyword(s):  
Close Association ◽  
Volcanic Belt ◽  
Granulite Facies ◽  
Mafic Rock ◽  
Crustal Extension ◽  
Potential Influence ◽  
Grenville Province ◽  
Show Evidence ◽  
Grenvillian Orogeny ◽  
First Time

Remnants of a ca. 1.24 Ga old volcanic belt formed in a within-plate setting (Manicouagan Crustal Extension Belt) are exposed over several tens of kilometres in the hinterland of the central Grenville Province, and can be recognized despite granulite-facies Grenvillian metamorphism and deformation. This belt mainly consists of layered felsic–mafic rock units, some of which are documented here for the first time. In the vicinity of the 1.24 Ga belt, a Geon 14 arc-related mafic suite and a Geon 15 metasedimentary package were pervasively injected by felsic (and mafic) material, show evidence of a Geon 12 thermal event, and therefore may represent remnants of rifted crust. Following Geon 12 crustal extension, lithospheric-scale magmatic activity in the immediate region continued intermittently, producing mafic dykes at 1.17 Ga and anorthosite at 1.16 and 1.05 Ga. A close association to 1.16 Ga or younger anorthosite is conspicuous to several Geon 12 rock units known in the central and eastern Grenville Province. We therefore suggest that subsequent anorthositic magmatism was focused on zones of lithospheric weakness inherited from Geon 12 crustal extension and remained active intermittently until the end of the Grenvillian orogeny.

Metamorphic constraints on the evolution of the gneisses from the parautochthonous and allochthonous polycyclic belts, Grenville Province, western Quebec

1990 ◽  
Vol 27 (3) ◽  
pp. 357-370 ◽  
Author(s):  
A. Indares ◽  
J. Martignole
Keyword(s):  
Granulite Facies ◽  
Ultramafic Rocks ◽  
Significant Discrepancy ◽  
Grenville Province ◽  
Narrow Strip ◽  
Metasedimentary Rocks ◽  
Metamorphic History ◽  
Tectonic Transport ◽  
History Of ◽  
Grenvillian Orogeny

The tectono-metamorphic history of polycyclic "grey gneisses" located in the central Grenville Province of western Quebec has been constrained along a transect perpendicular to the length of the Grenville Orogen. Two terranes, the Réservoir Dozois terrane (RDT) and the Réservoir Baskatong terrane (RBT), were recognized from their structural, lithological, and geochronological characteristics. This subdivision has been confirmed by application of geothermobarometric techniques to appropriate mineral assemblages.The RDT is the southern extension of the parautochthonous belt of the Grenville Province, which in this area is composed of Archean rocks of upper-amphibolite grade. During the Grenvillian Orogeny, northwest-directed thrusting resulted in the tectonic burial of this terrane as a single tectonic unit, in contrast with the northern part of the parautochthonous belt, where several slices were imbricated against the Grenville Front. Maximum P–T conditions in the RDT (850 MPa, 720 °C) were likely Grenvillian and were followed by pervasive retrogression down to the hornblende–epidote subfacies. Locally, the RDT is overlain by remnants of thrust slices composed of monocyclic metasedimentary rocks that were deformed and metamorphosed in the granulite facies during the Grenvillian Orogeny.To the southeast, the RBT is an allochthonous or exotic terrane probably of Proterozoic age. It also experienced tectonic burial by thrusting (1030 MPa, 710 °C) during the Grenvillian Orogeny, whose thermal climax (790 °C) coincided with charnockite emplacement during decompression to 850 MPa.These two terranes are separated by a narrow strip of sheared rocks, the Renzy shear belt (RSB), which comprises mafic and ultramafic rocks subjected to high P and T (975 MPa, 745 °C). In view of the significant discrepancy between the metamorphic histories of the two terranes separated by the RSB, major tectonic transport has to be envisaged along this zone.

Pre-Kenoran Tonalitic Gneisses in the Grenville Province

1975 ◽  
Vol 12 (5) ◽  
pp. 844-849 ◽  
Author(s):  
R. A. Frith ◽  
R. Doig
Keyword(s):  
Granulite Facies ◽  
Retrograde Metamorphism ◽  
Initial Ratio ◽  
Fold Belt ◽  
Grenville Province ◽  
Tonalitic Gneiss ◽  
Grenvillian Orogeny

Rb–Sr whole-rock studies of tonalitic gneiss within the Grenville Province on the eastern extension of the Abitibi fold belt may indicate an age greater than 3000 m.y. The gneiss samples were collected up to 32 miles (52 km) from the Grenville Front. Rocks beyond this generally show the effects of the Grenvillian orogeny about 1100 m.y. ago which raised the 87Rb/86Sr initial ratio from about 0.7025 to 0.7148. Rocks more than 40 miles (64 km) from the Grenville Front show retrograde metamorphism from the granulite facies that is considered to be related to the metamorphism associated with the intrusion of anorthosite still farther to the southeast (ca. 1500 m.y.). The Archean tonalitic gneisses exhibit E–W and NE–SW aeromagnetic trends but similar rocks to the southeast exhibit aeromagnetic patterns that are chiefly N–S and may be a result of Hudsonian deformation. A small granitic body in this zone of N–S aeromagnetic pattern was intruded 1745 ± 23 m.y. ago(87Rb λ = 1.39 × 10−11y−1).

scholarly journals The geology and structural setting of the Proterozoic Ammassalik Intrusive Complex, East Greenland

1989 ◽  
Vol 146 ◽  
pp. 41-45
Author(s):  
C.R.L Friend ◽  
A.P Nutman
Keyword(s):  
Contact Zone ◽  
Magma Mixing ◽  
Granulite Facies ◽  
Intrusive Complex ◽  
East Greenland ◽  
Structural Setting ◽  
Dehydration Reactions

The rocks of the Ammassalik area comprise reworked Archaean gneisses and a variety of mainly pelitic to psammitic Proterozoic metasediments. Proterozoic deformation caused thrust intercalation of the rocks and folded them into overturned, southerly directed nappes. Three dioritic centres, collectively named the 'Ammassalik Intrusive Complex' in this paper, were emplaced into a tract occupied by metasediments, causing extensive anatexis. The granitic liquids produced from this resulted in magma mixing with the still liquid diorite; they also formed discrete sheets of augen granite intruding the country rocks. The diorite centres were emplaced as relatively dry bodies, and together with anatexis, they caused the formation of granulite facies assemblages by dehydration reactions in the country rocks. Further away from the contact zone garnet appeared in the surrounding grey gneisses.

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