A gravity profile across southern Saganash Lake fault: implications for the origin of the Kapuskasing Structural Zone

Nitescu, Bogdan; Halls, H. C.

doi:10.1139/e01-100

Cited by 9 publications

(3 citation statements)

References 22 publications

(28 reference statements)

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“…The Wawa Gneiss Domain is separated from the granulite facies (deep crust) Kapuskasing Structural Zone to the east by a gradational metamorphic contact (Percival, 1983). Shear zones define the most pervasive fabric in the Wawa Gneiss Domain, becoming ubiquitous and defining the regional scale Saganash Lake fault when approaching the Kapuskasing Structural Zone (Moser, 1994; Nitescu & Halls, 2002). The hornblende–biotite gneisses of the Wawa Gneiss Domain enclose metre‐ to decametre‐sized hornblende–plagioclase–clinopyroxene rafts (Figure 2b), which are commonly crosscut by granodiorite dykes and quartz‐monzonite pegmatites (Percival, 1990).…”

Section: Regional Geologymentioning

confidence: 99%

Redistribution of heat‐producing elements during melting of Archean crust

Kinney,

Kendrick,

Duguet

et al. 2023

Journal Metamorphic Geology

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Heat generated from the decay of K, Th, and U plays a fundamental role in the differentiation and stabilization of Earth's continental crust. This is particularly important in the construction of Archean cratons that form the nuclei of Earth's continents. The Kapuskasing uplift is a rare exposure of an Archean‐age crustal cross‐section that provides a snapshot of crustal melting, differentiation, and compositional stratification. We integrate field observations, whole‐rock compositions, thermodynamic equilibrium and accessory mineral modelling with heat production and latency time modelling to provide insights into the partitioning of heat‐producing elements between residue and melt during anatexis of metabasites as well as the resulting effects on metamorphic timescales and the production of tonalite–trondhjemite–granodiorite (TTG) suites. We model six metabasite compositions ranging from relatively fertile greenschist facies metabasites to melt‐depleted residual mafic (upper‐)amphibolites to granulites. Heat‐producing elements are modelled to be partitioned between melt and residue; the dominant minerals in the residue that host these elements are apatite, hornblende, K‐feldspar, and epidote. At 800–850°C epidote is no longer stable, and the melt fraction is predicted to contain roughly half of the heat production capacity for the system. Apatite and melt are expected to be the dominant repositories for Th and U during anatexis; zircon is predicted to be completely consumed by 850°C, whereas apatite persists to higher temperatures and allanite is expected only in minor modal abundances at high‐P, low‐T conditions. The partitioning of heat‐producing elements into relatively low‐density melt decreases the heat production of the residual system during anatexis. Due to their high density and affinity for U and Th, epidote and apatite retain heat production capacity in the residue during metabasite melting. Thermal latency modelling of metamorphism suggests that enriched metabasite compositions require 38–46 My to increase the temperature from ~650 to 850°C (solidus temperature to peak metamorphic temperature of the Kapuskasing uplift), whereas estimates are considerably shorter for depleted compositions (7–25 My). Four of the six samples modelled require 60–70 My to reach 1000°C from the solidus. Our modelling of heat‐producing element partitioning and predicted proportions of melt suggest that enriched basaltic compositions are the most reasonable source of TTG magmas and our heating time modelling indicates the mantle as an equal to dominant source of heat for metabasite anatexis compared with radiogenic heat production.

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Section: Regional Geologymentioning

confidence: 99%

Redistribution of heat‐producing elements during melting of Archean crust

Kinney,

Kendrick,

Duguet

et al. 2023

Journal Metamorphic Geology

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“…1) is the largest and the most extensively studied. The smaller Swayze greenstone belt is situated in the western part of the Abitibi Subprovince (Figs 1 & 2), where its western limit corresponds to the Kapuskasing structure, a Proterozoic uplift of Archaean high-grade metamorphic rocks corresponding to a crustal-scale thrust or flower structure (Percival 1988;Nitescu & Halls 2002). The Kenogamissi complex, a large crystalline complex composed of multiple plutons of distinctly different ages, straddles the boundary between the Abitibi and Swayze greenstone belts (Fig.…”

Section: Geological Settingmentioning

confidence: 99%

Late Archaean Kenogamissi complex, Abitibi Subprovince, Ontario, Canada: doming, folding and deformation-assisted melt remobilisation during syntectonic batholith emplacement

Benn

2004

Earth and Environmental Science Transactions of the Royal Socie

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The Kenogamissi complex represents a large exposure of folded Late Archaean crystalline crust exposed within the Abitibi Subprovince, Ontario, Canada. It is composed of an heterogeneous amphibolite-grade orthogneiss unit, and several generations of batholiths and plutons of tonalite, granodiorite and granite composition. Together, the various units represent granitic magmatism during the period from 2740 Ma to 2660 Ma. Structural mapping and petrographic studies were focused on the orthogneiss unit (2723 Ma), on the newly defined Roblin tonalitegranodiorite batholith (ca. 2713 Ma) and on the highly strained metavolcanic rocks within the deformation aureole that surrounds the Kenogamissi complex. Structural analysis indicates that the Kenogamissi complex was emplaced into the greenstones as a dome that caused severe flattening and recumbent F2 refolding of earlier F1 folds in the deformation aureole. Doming is interpreted to be caused by the emplacement and inflation of tonalite-granodiorite batholiths, such as the Roblin Batholith, into the actively folding Swayze greenstone belt. Continued regional folding resulted in F3 refolding of F1 and F2 in the deformation aureole. Continued regional folding also deformed and folded the Kenogamissi complex and resulted in further uplift and emplacement of the complex into the greenstone belt. The early-formed magmatic foliation and compositional layering in the Roblin Batholith were folded by F3 while the batholith was still a crystal mush, and an F3 axial-surface magmatic foliation was locally formed. Folding of the partially molten Roblin Batholith also resulted in the remobilisation of fractionated liquids into shear zones which formed on the limbs of the F3 magmatic folds. Similar structures are present in the orthogneiss unit and are interpreted to represent remobilisation of melts which intruded the orthogneiss at the time of emplacement of the Roblin Batholith. The formation of the dykes on sheared fold limbs may be attributed to increased dilatancy during localised shearing of the crystal mush. Deformation-assisted remobilisation and extraction of fractionated liquids, and the possible transport of the fractionated liquids to higher levels in the crystallising Roblin Batholith, may have played a role in its magmatic differentiation.

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“…For example, Halls and Mound (1998), and Nitescu and Halls (2002) established the faultdeveloping situation in the Kapuskasing structural zone with gravity profile and GPS data. Meng et al (1990), Wang et al (1997), and Yang et al (2015) all found crustal block structures using gravity profile data and so on.…”

Section: Introductionmentioning

confidence: 99%

Gravity anomaly and crustal density structure in Jilantai rift zone and its adjacent region

Shen

Tan

et al. 2016

Earthq Sci

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This paper deals with the interpretation of Bouguer gravity anomalies measured along a 250 km long Suhaitu-Etuokeqi gravity profile located at the transitional zone of the Alxa and Ordos blocks where geophysical characteristics are very complex. The analysis is carried out in terms of the ratio of elevation and Bouguer gravity anomaly, the normalized full gradient of a section of the Bouguer gravity anomaly (G h ) and the crustal density structure reveal that (1) the ratio of highs and lows of elevation and Bouguer gravity anomaly is large between Zhengyiguan fault (F4) and Helandonglu fault (F6), which can be explained due to crustal inhomogeneities related to the uplift of the Qinghai-Tibet block in the northeast; (2) the main active faults correspond to the G h contour strip or cut the local region, and generally show strong deformation characteristics, for example the Bayanwulashan mountain front fault (F1) or the southeast boundary of Alxa block is in accord with the western change belt of G h , a belt about 10 km wide that extends to about 30 km; (3) YinchuanPingluo fault (F8) is the seismogenic structure of the Pingluo M earthquake, and its focal depth is about 15 km; (4) the Moho depth trend and Bouguer gravity anomaly variation indicates that the regional gravity field is strongly correlated with the Moho discontinuity.

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A gravity profile across southern Saganash Lake fault: implications for the origin of the Kapuskasing Structural Zone

Cited by 9 publications

References 22 publications

Redistribution of heat‐producing elements during melting of Archean crust

Redistribution of heat‐producing elements during melting of Archean crust

Late Archaean Kenogamissi complex, Abitibi Subprovince, Ontario, Canada: doming, folding and deformation-assisted melt remobilisation during syntectonic batholith emplacement

Gravity anomaly and crustal density structure in Jilantai rift zone and its adjacent region

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