Evolution of the sublayer of the Sudbury Igneous Complex: geochemical, Sm–Nd isotopic and petrologic evidence

Prevec, Stephen A.; Lightfoot, Peter C.; Keays, Reid R.

doi:10.1016/s0024-4937(00)00005-0

Cited by 45 publications

(39 citation statements)

References 21 publications

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“…The source of the ultramafic material has therefore been interpreted as crucial to the understanding of the origin and development of the sulphide ores. Recent petrological, geochemical, and isotopic work [Lightfoot et al, 1997;Prevec, 2000;Prevec et al, 2000] has demonstrated that the ultramafic material is consistent with derivation by crystallization from within the SIC and not from an external source.…”

Section: Contact Sublayermentioning

confidence: 84%

Thermal evolution and interaction between impact melt sheet and footwall: A genetic model for the contact sublayer of the Sudbury Igneous Complex, Canada

Prevec

Cawthorn

2002

J. Geophys. Res.

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[1] The Sudbury Igneous Complex (SIC) and associated Ni-Cu-PGE mineralization has been interpreted in terms of a large meteorite impact event. In this study, the thermal relationship between the large cooling melt sheet and the surrounding country rock is examined in terms of its role in an evolving thermal gradient rather than as a passive receptacle for the melt sheet above. Thermal modeling of this environment is undertaken using physical and thermal constraints appropriate to the SIC and assuming heat dissipation from the 2.5-km-thick superheated melt sheet (!1800°C) by either diffusion with zero convection or by rapid convection within the melt sheet. With zero convection, basal cooling produces a solid base, which lowers conductivity such that the immediate footwall rocks reach 1000°C, producing partial melting that extends 200 m into the footwall. In a rapidly convecting melt sheet the initial footwall chill is remelted and high temperatures maintained within the sheet close to the contact. This results in higher temperatures being attained in the immediate footwall (1100-1200°C), inducing complete melting of proximal footwall and partial melting to depths of 500 m below the melt sheet. Proximal footwall consists of Paleoproterozoic Huronian basalts, granitoids and sediments, exposed in the south range, overlying Archaean gneisses and granitoids. Total and partial melting of this material early in the cooling history of the melt sheet and the subsequent gravitational accommodation of these melts according to density would produce a basalt-dominated basal liquid corresponding to the so-called contact sublayer. The thermal aureole predicted by our models is consistent with that preserved around the north range of the SIC assuming $800 m of thermally induced erosion at the contact.

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Section: Contact Sublayermentioning

confidence: 84%

Thermal evolution and interaction between impact melt sheet and footwall: A genetic model for the contact sublayer of the Sudbury Igneous Complex, Canada

Prevec

Cawthorn

2002

J. Geophys. Res.

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“…Chemical zoning has also been recognized for other Offset Dikes and attributed to (1) flow differentiation (Grant and Bite 1984;Prevec et al 2000), (2) multiple injection of melt either during the differentiation of the Main Mass of the SIC and Sublayer (Grant and Bite 1984;Ostermann et al 1995) or (4) late magmatic (deuteric) alteration (Grant and Bite 1984;Deutsch 1994;Corfu and Lightfoot 1996;Therriault et al 2002). In order to assess these mechanisms, we discuss individual processes of differentiation for the Worthington Dike.…”

Section: Mechanisms Of Dike Differentiationmentioning

confidence: 94%

“…The chemical distinction between Offset Dikes is similar to those of the North and South Range Sublayer, although in general the Offset Dikes are much more homogeneous compared to the Sublayer (Lightfoot et al 1997b). This chemical distinction between North and South Range Offset Dikes and Sublayer has been attributed to assimilation of host rocks, which differ between the North and South Ranges (Lightfoot et al 1997b;Prevec et al 2000). In the South Range, host rocks are composed of Paleoproterozoic rocks of the Huronian Supergroup, whereas in the North Range they are made up mostly of Archean metagranitoid rocks.…”

Section: Whole Rock Chemistrymentioning

confidence: 99%

“…Petrographical, chemical and isotopic heterogeneity of Offset Dikes and Sublayer is often attributed to assimilation of variable host rock types by the superheated melt sheet (Pattison 1979;Deutsch et al 1995;Lightfoot et al 1997b;Prevec 2000;Prevec et al 2000;Prevec and Cawthorn 2002). In particular, Offset Dikes and Sublayer show the same chemical differences between the South Range and North Table 1.…”

Section: Assimilation Of Host Rock Prior To Dike Emplacementmentioning

confidence: 99%

“…Existing rival interpretations are for example: (1) the Offset Dikes represent a melt that was geochemically equivalent to the Main Mass of the SIC before it differentiated (Lightfoot et al 1997b;Lightfoot and Farrow 2002;Tuchscherer and Spray 2002). (2) The dike melts derived from intermediate stages of fractional crystallization (± contamination) of the Main Mass of the SIC (Wood and Spray 1998;Prevec et al 2000;Therriault et al 2002), or (3) radial dikes including the Sublayer sensu stricto (Fig. 1b) are closely related to an endogenic intrusion that is younger than the granophyre Eckstrand 1993, 1994) and possibly younger than the norite (Dressler et al 1996).…”

Section: Introductionmentioning

confidence: 99%

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Differentiation and emplacement of the Worthington Offset Dike of the Sudbury impact structure, Ontario

Hecht

Wittek

Riller

et al. 2008

Meteorit & Planetary Scien

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Abstract-The Offset Dikes of the 1.85 Ga Sudbury Igneous Complex (SIC) constitute a key topic in understanding the chemical evolution of the impact melt, its mineralization, and the interplay between melt migration and impact-induced deformation. The origin of the melt rocks in Offset Dikes as well as mode and timing of their emplacement are still a matter of debate. Like many other offset dikes, the Worthington is composed of an early emplaced texturally rather homogeneous quartz-diorite (QD) phase at the dike margin, and an inclusion-and sulfide-rich quartz-diorite (IQD) phase emplaced later and mostly in the centre of the dike. The chemical heterogeneity within and between QD and IQD is mainly attributed to variable assimilation of host rocks at the base of the SIC, prior to emplacement of the melt into the dike. Petrological data suggest that the parental magma of the Worthington Dike mainly developed during the pre-liquidus temperature interval of the thermal evolution of the impact melt sheet (>1200 °C). Based on thermal models of the cooling history of the SIC, the two-stage emplacement of the Worthington Dike occurred likely thousands to about ten thousand years after impact. Structural analysis indicates that an alignment of minerals and host rock fragments within the Worthington Dike was caused by ductile deformation under greenschist-facies metamorphic conditions rather than flow during melt emplacement. It is concluded that the Worthington Offset Dike resulted from crater floor fracturing, possibly driven by late-stage isostatic readjustment of crust underlying the impact structure.

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Economic Mineral Deposits in Impact Structures: A Review

et al.

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Evolution of the sublayer of the Sudbury Igneous Complex: geochemical, Sm–Nd isotopic and petrologic evidence

Cited by 45 publications

References 21 publications

Thermal evolution and interaction between impact melt sheet and footwall: A genetic model for the contact sublayer of the Sudbury Igneous Complex, Canada

Thermal evolution and interaction between impact melt sheet and footwall: A genetic model for the contact sublayer of the Sudbury Igneous Complex, Canada

Differentiation and emplacement of the Worthington Offset Dike of the Sudbury impact structure, Ontario

Economic Mineral Deposits in Impact Structures: A Review

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