Intrasedimentary magnetization by vertical fluid flow and exotic geochemistry

Peirce, John W.; Goussev, Serguei; Charters, Robert A.; Abercrombie, Hugh J.; DePaoli, Glen R.

doi:10.1190/1.1437840

Cited by 25 publications

(9 citation statements)

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“…There are numerous mechanisms for the origin of the CRM in pyrrhotite including oxidation of preexisting pyrite [Salmon et al, 1988], hydrocarbon migration [Machel and Burton, 1991], diagenesis of gas hydrates [Housen and Musgrave, 1996;Larrasoaña et al, 2007] release of trapped pore fluids [Urbat et al, 2000], magnetite reacting with pyrite under reducing conditions during burial metamorphism [Gillett, 2003], low-grade metamorphic reactions [Appel et al, 2012], and low-temperature burial diagenesis [Aubourg and Pozzi, 2010]. Another mechanism for formation of pyrrhotite is thermochemical sulfate reduction (TSR) [Pierce et al, 1998]. TSR reactions occur in localized areas [Machel, 2001] and have numerous by-products including the following: milky calcite, saddle dolomite, iron sulfides including pyrrhotite and pyrite, H2S (sour gas), methane, and sometimes elemental S [Machel et al, 1995;Machel, 2001].…”

Section: Discussionmentioning

confidence: 99%

An integrated paleomagnetic, rock magnetic, and geochemical study of the Marcellus shale in the Valley and Ridge province in Pennsylvania and West Virginia

Manning

Elmore

2015

JGR Solid Earth

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An integrated paleomagnetic, rock magnetic, and diagenetic study of the Devonian Marcellus Subgroup from threefolds in the Valley and Ridge province in Pennsylvania and West Virginia indicates that the unit contains an intermediate temperature chemical remanent magnetization (CRM) with south-southeast declinations and shallow negative inclinations residing in pyrrhotite and a CRM with more southerly declinations and shallow positive inclinations residing in magnetite. Rock magnetic results confirm the presence of pyrrhotite and magnetite. Tilt tests indicate that pyrrhotite and magnetite CRMs are syntilting to posttilting, and paleopoles for both CRMs are similar and plot on the Permian part of the apparent polar wander path for North America. The Marcellus Subgroup has a complex paragenetic sequence which includes bitumen deposition and vein formation. The magnetite and pyrrhotite CRMs formed in the Permian, probably due to burial diagenetic processes and not orogenic fluids. The base of the unit contains the highest total organic content (TOC) values and highest magnetic intensities, both of which decrease up section. This connection between TOC and magnetic intensity suggests that the magnetite formed as a result of the maturation of the organic matter although more work is needed to test this hypothesis. The pyrrhotite may have formed as a result of thermochemical sulfate reduction involving organic matter during the production of methane in this gas reservoir. The similar Permian CRM ages may be explained by thrusting which resulted in rapid burial of the Marcellus Subgroup as it passed through the oil window and into the gas window quickly producing magnetite and pyrrhotite, respectively.

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Section: Discussionmentioning

confidence: 99%

An integrated paleomagnetic, rock magnetic, and geochemical study of the Marcellus shale in the Valley and Ridge province in Pennsylvania and West Virginia

Manning

Elmore

2015

JGR Solid Earth

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“…Although some of the remagnetizations are thermoviscous in origin (Kligfield & Channell 1981), many are interpreted to be chemical in origin with several remagnetization mechanisms proposed. These include pyrrhotite authigenesis caused by thermochemical sulphate reduction (Pierce et al 1998;Zechmeister et al 2012), migration of hydrocarbons (Machel & Burton 1991) or oxidation of pre-existing pyrite (Salmon et al 1988). Chemical alteration by gas hydrates (Housen & Musgrave 1996;Larrasoaña et al 2007) and pore fluids (Urbat et al 2000) have also been suggested as mechanisms.…”

Section: Other Remagnetization Mechanismsmentioning

confidence: 99%

“…Some studies have presented evidence that secondary magnetite could be responsible for magnetic enhancement in soil polluted by hydrocarbons (Rijal et al 2010). Pyrrhotite can also form during thermochemical sulphate reduction of hydrocarbons (Pierce et al 1998); this has been proposed as a mechanism for acquisition for a CRM in pyrrhotite Zechmeister et al 2012). In some hydrocarbonimpregnated units, magnetite is present but it does not carry a stable remanence; in some red beds, hydrocarbons can cause a net decrease in magnetization by dissolving haematite (e.g.…”

Section: Hydrocarbonsmentioning

confidence: 99%

Remagnetization and chemical alteration of sedimentary rocks

Elmore

Muxworthy

Aldana

2012

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Chemical remagnetization is a very common phenomenon in sedimentary rocks and developing a greater understanding of the mechanisms has several benefits. Acquisition of a secondary magnetization is usually tangible evidence of a diagenetic event that can be dated by isolation of the chemical remanent magnetization and comparison of the pole position to the apparent polar wander path. This can be important because diagenetic investigations are frequently limited by the difficulty in constraining the time frames in which most past events have occurred. Remagnetization can commonly obscure a primary magnetization; developing a better understanding of remagnetization could improve our ability to uncover primary magnetizations. Many chemical remagnetization mechanisms have been proposed, including those associated with chemical alteration by a number of different fluids (orogenic, basinal and hydrocarbons), burial diagenetic processes (clay diagenesis and maturation of organic matter) or other processes. This paper summarizes our current knowledge of these chemical remagnetization mechanisms, with a focus on examples where there is a connection with chemical alteration.

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“…[28] A coincidence of faults with magnetic lineaments has been previously observed elsewhere and was interpreted in different ways. Peirce et al [1998] claimed that roughly 25% of the seismically visible faults in their study area can be detected magnetically, but numerous fractures, not detected seismically, can also be seen in HRAM surveys. They attributed their observations to exotic minerals being deposited in faults and fractures by redox processes induced by vertical flow of water [Pierce Sherrod et al [2005] have interpreted buried reverse faults in the Puget Sound area, Washington, from HRAM data, ground magnetic surveys, susceptibility measurements and trenching.…”

Section: Discussion: Why Is the Fault Zone Visible In The Aeromagnetimentioning

confidence: 99%

Magnetic character of a large continental transform: An aeromagnetic survey of the Dead Sea Fault

Brink

Rybakov

Al-Zoubi

et al. 2007

Geochem Geophys Geosyst

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[1] New high-resolution airborne magnetic (HRAM) data along a 120-km-long section of the Dead Sea Transform in southern Jordan and Israel shed light on the shallow structure of the fault zone and on the kinematics of the plate boundary. Despite infrequent seismic activity and only intermittent surface exposure, the fault is delineated clearly on a map of the first vertical derivative of the magnetic intensity, indicating that the source of the magnetic anomaly is shallow. The fault is manifested by a 10-20 nT negative anomaly in areas where the fault cuts through magnetic basement and by a <5 nT positive anomaly in other areas. Modeling suggests that the shallow fault is several hundred meters wide, in agreement with other geophysical and geological observations. A magnetic expression is observed only along the active trace of the fault and may reflect alteration of magnetic minerals due to fault zone processes or groundwater flow. The general lack of surface expression of the fault may reflect the absence of surface rupture during earthquakes. The magnetic data also indicate that unlike the San Andreas Fault, the location of this part of the plate boundary was stable throughout its history. Magnetic anomalies also support a total left-lateral offset of 105-110 km along the plate boundary, as suggested by others. Finally, despite previous suggestions of transtensional motion along the Dead Sea Transform, we did not identify any igneous intrusions related to the activity of this fault segment.

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Intrasedimentary magnetization by vertical fluid flow and exotic geochemistry

Cited by 25 publications

References 0 publications

An integrated paleomagnetic, rock magnetic, and geochemical study of the Marcellus shale in the Valley and Ridge province in Pennsylvania and West Virginia

An integrated paleomagnetic, rock magnetic, and geochemical study of the Marcellus shale in the Valley and Ridge province in Pennsylvania and West Virginia

Remagnetization and chemical alteration of sedimentary rocks

Magnetic character of a large continental transform: An aeromagnetic survey of the Dead Sea Fault

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