Geology, Sudbury bedrock compilation, Ontario

Ames, D E; Davidson, A; Buckle, J L; Card, K D

doi:10.4095/221501

Cited by 28 publications

(14 citation statements)

References 0 publications

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“…This Ir anomaly has higher values than the average of the marginal phase of the Worthington Offset dike (0.22 ppb), the composition of which Keays and Lightfoot (2004) considered a proxy for that of the initial SIC, and it has been attributed to an admixture of meteoritic material (Mungall et al. 2004; Ames et al. 2005, 2008).…”

Section: Working Hypothesismentioning

confidence: 88%

“…1999) and an iridium anomaly, which has been interpreted to be meteoritic in origin (Mungall et al. 2004; Ames et al. 2005, 2008).…”

Section: Overall Character Of the Onapingmentioning

confidence: 99%

“…The general description of the Onaping that follows is based largely on the mapping by Gibbins (1994), Ames (1999), Ames and Gibson (2004a, 2004b, 2004c, 2004d, 2004e), Gibbins et al. (2004) and Ames et al. (2005), to which the reader is referred for considerably more detail.…”

Section: Overall Character Of the Onapingmentioning

confidence: 99%

“…This portion of the melt sheet would further lose thermal energy through the latent heat of melting as it attempted to assimilate the clastic debris. This likely resulted in the formation of an upper chill zone of roof rocks, remnants of which may be the now discontinuous, broadly concordant phase of the Onaping intrusion present at ∼50% of the SIC‐Onaping contact (Ames et al. 2005, 2008).…”

Section: Working Hypothesismentioning

confidence: 99%

“…The contacts, however, between these units are chemically and mineralogically gradational and the terms Norite and Quartz Gabbro are largely misnomers for these lithologies (Therriault et al. 2002; Ames et al. 2005).…”

Section: Introductionmentioning

confidence: 99%

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The evolution of the Onaping Formation at the Sudbury impact structure

Grieve

Ames

Morgan

et al. 2010

Meteorit & Planetary Scien

168

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Abstract-The 1.4-1.6 km thick Onaping Formation consists of a complex series of breccias and ''melt bodies'' lying above the Sudbury Igneous Complex (SIC) at the Sudbury impact structure. Based on the presence of shocked lithic clasts and various ''glassy'' phases, the Onaping has been described as a ''suevitic'' breccia, with an origin, at least in part, as fallback material. Recent mapping and a redefined stratigraphy have emphasized similarities and differences in its various vitric phases, both as clast types and discrete intrusive bodies. The nature of the Onaping and that of other ''suevitic'' breccias overlying impact melt sheets is reviewed. The relative thickness, internal stratigraphic and lithological character, and the relative chronology of depositional units indicate multiple processes were involved over some time in the formation of the Onaping. The Sudbury structure formed in a foreland basin and water played an essential role in the evolution of the Onaping, as indicated by a major hydrothermal system generated during its formation. Taken together, observations and interpretations of the Onaping suggest a working hypothesis for the origin of the Onaping that includes not only impact but also the interaction of sea water with the impact melt, resulting in repeated explosive interactions involving proto-SIC materials and mixing with pre-existing lithologies. This is complicated by additional brecciation events due to the intrusion of proto-SIC materials into the evolving and thickening Onaping. Fragmentation mechanisms changed as the system evolved and involved vesiculation in the formation of the upper two-thirds of the Onaping.

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Section: Working Hypothesismentioning

confidence: 88%

“…1999) and an iridium anomaly, which has been interpreted to be meteoritic in origin (Mungall et al. 2004; Ames et al. 2005, 2008).…”

Section: Overall Character Of the Onapingmentioning

confidence: 99%