The Iceland crust: Evidence from drillhole data on structure and processes

Pálmason, Guðmundur; Arnórsson, Stefán; Friðleifsson, Ingvar Birgir; Kristmannsdóttir, Hrefna; Sæmundsson, Kristján; Stefansson, V.; Steingrímsson, Benedikt; Tómasson, Jens; Kristjánsson, Leó

doi:10.1029/me002p0043

Cited by 70 publications

(37 citation statements)

References 22 publications

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“…However, rare chlorite was identified within a metamorphosed basement clast but is not related to impact-induced hydrothermal activity. Zeolites characteristic of slightly higher temperature formation (100-200 °C; Palmason et al 1979) are not present in the drilled impactite sequence. Therefore, the assemblages of secondary minerals in Yax-1 that consist of clay minerals, celadonite, saponite, montmorillonite, opal, magnetite, limonite, goethite, K-feldspar, carbonate, and trace sulfides, formed at low (<150 °C) temperatures (Ames et al 2004).…”

Section: Consequences For Anomaly Interpretationmentioning

confidence: 99%

Magnetic mineralogy of the Yaxcopoil‐1 core, Chicxulub

Pilkington

Ames

Hildebrand

2004

Meteorit & Planetary Scien

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Abstract-Core from the Yaxcopoil-1 (Yax-1) hole, drilled as a result of the Chicxulub Scientific Drilling Project (CSDP), has been analyzed to investigate the relationship between opaque mineralogy and rock magnetic properties. Twenty one samples of suevite recovered from the depth range 818-894 m are generally paramagnetic, with an average susceptibility of 2000 × 10 −6 SI and have weak remanent magnetization intensities (average 0.1 A/m). The predominant magnetic phase is secondary magnetite formed as a result of low temperature (<150 °C) alteration. It occurs in a variety of forms, including vesicle infillings associated with quartz and clay minerals and fine aggregates between plagioclase/diopside laths in the melt. Exceptional magnetic properties are found in a basement clast (metamorphosed quartz gabbro), which has a susceptibility of >45000 × 10 −6 SI and a remanent magnetization of 77.5 A/m. Magnetic mafic basement clasts are a common component in the Yax-1 impactite sequence. The high susceptibility and remanence in the mafic basement clasts are caused by the replacement of amphiboles and pyroxenes by an assemblage with fine <1 µm magnetite, ilmenite, K-feldspar, and stilpnomelane. Replacement of the mafic minerals by the magnetic alteration assemblage occurred before impact. Similar alteration mechanisms, if operative within the melt sheet, could explain the presence of the high amplitude magnetic anomalies observed at Chicxulub.

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Section: Consequences For Anomaly Interpretationmentioning

confidence: 99%

Magnetic mineralogy of the Yaxcopoil‐1 core, Chicxulub

Pilkington

Ames

Hildebrand

2004

Meteorit & Planetary Scien

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“…The observed secondary mineralogy of Hole 747C basalts bears some resemblance to that observed in regions of high heat flow in the extensive subaerial tholeiitic flood basalts of Iceland (Kristmannsdòttir and Tòmasson, 1978;Pàlmason et al, 1979). The zeolite assemblages correspond to the intermediate temperature (between 50°C and 100°C) zone of the zeolite facies.…”

Section: Alterationmentioning

confidence: 96%

“…The secondary mineralogy of the Site 747 basalts is reminiscent of those from regions of high heat flow in the extensive subaerial tholeiitic flood basalts of Iceland (Kristmannsdòttir and Tòmasson, 1978;Pàlmason et al, 1979).…”

Section: Seismic Stratigraphy Depositional and Tectonic Historymentioning

confidence: 99%

Site 747

1989

Proceedings of the Ocean Drilling Program

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“…The observed secondary mineralogy of Hole 749C bears some resemblance to that of high heat flow in the extensive subaerial tholeiitic flood basalts of Iceland (Kristmannsdòttir and Tòmasson, 1978;Pàlmason et al, 1979). The presence of laumontite and interlayered smectites corresponds to the high-temperature (100°-200°C) zone of the zeolite facies.…”

Section: Alterationmentioning

confidence: 96%

Site 749

1989

Proceedings of the Ocean Drilling Program

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Basement at this site corresponds to a very strong reflector. An approach site survey located the site on Marion Dufresne MCS line MD47-13 (shot point 5670) where the basement reflector lies at about 0.24 s two-way traveltime (TWT) below seafloor. Downslope the sediments thicken in all directions, especially by toplap. Thus, the oldest sediment cored at this site will not correspond to the age of basement.The upper 43.8 m of section was cored with 100% recovery using the advanced hydraulic piston corer (APC), at which point middle Eocene cherts were encountered that reduced recovery via the APC and the extended core barrel (XCB) to only 26% over the next 80 m. A change to the rotary core barrel (RCB) yielded only 7% recovery through cherts, chalks, and oozes to the basement contact at 202 m. After obtaining 5 m of basalt in the next core, the succeeding two cores were essentially empty, and a model Lamar Hayes (LH) minicone was deployed to allow the hole to be reentered after a bit change. This was the first use of a free-fall minicone for a dedicated basement site.Inspection of the bottom hole assembly (BHA) on deck showed that severe pounding of the bit against hard bottom in high seas at this shallow site had resulted in a badly worn bit and a broken flapper valve. The latter had precluded any recovery in the last two

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The Iceland crust: Evidence from drillhole data on structure and processes

Cited by 70 publications

References 22 publications

Magnetic mineralogy of the Yaxcopoil‐1 core, Chicxulub

Magnetic mineralogy of the Yaxcopoil‐1 core, Chicxulub

Site 747

Site 749

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