Dating diagenetic monazite in mudrocks: Constraining the oil window?

J. A. Evans; J. A. Zalasiewicz; B. Rasmussen; I. Fletcher; Nicholas J. G. Pearce

doi:10.1144/0016-764902-066

Dating diagenetic monazite in mudrocks: Constraining the oil window?

J. A. Evans, J. A. Zalasiewicz, B. Rasmussen, I. Fletcher, Nicholas J. G. Pearce

Department of Geography and Earth Sciences

Research output: Contribution to journal › Article › peer-review

54 Citations (Scopus)

Abstract

Authigenic monazite nodules, increasingly recognized in Pre-Mesozoic mudrock successions, provide a means for dating diagenesis by exploiting trace uranium within the monazite structure. But, dating is difficult in practice because of zonation and abundant host rock inclusions. We report here a refined technique that has yielded a date of 419 ± 14 Ma 2σ MSWD = 1.2 for a 17-point Pb–Pb regression age from a Telychian (Silurian: late Llandovery) mudrock from central Wales. SHRIMP analyses of monazite nodules from the same horizon are consistent with this, and additionally demonstrate concordance of the U–Pb and Th–Pb systems. These results open the door to providing robust dates for a phase of burial-related diagenesis which, in Wales, seems approximately coincident with, and perhaps was related to, hydrocarbon expulsion.

Original language	English
Pages (from-to)	619-622
Number of pages	4
Journal	Journal of the Geological Society
Volume	159
DOIs	https://doi.org/10.1144/0016-764902-066
Publication status	Published - 01 Dec 2002

Keywords

palaeozoic
Welsh Basin
oil window
monazite
RARE-EARTH ELEMENTS
U-PB
COLLOIDAL PARTICLES
NORTH WALES
WELSH BASIN
FRACTIONATION
METAMORPHISM
ASSEMBLAGES
CARBONATES
URANIUM

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http://hdl.handle.net/2160/7559

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title = "Dating diagenetic monazite in mudrocks: Constraining the oil window?",

abstract = "Authigenic monazite nodules, increasingly recognized in Pre-Mesozoic mudrock successions, provide a means for dating diagenesis by exploiting trace uranium within the monazite structure. But, dating is difficult in practice because of zonation and abundant host rock inclusions. We report here a refined technique that has yielded a date of 419 ± 14 Ma 2σ MSWD = 1.2 for a 17-point Pb–Pb regression age from a Telychian (Silurian: late Llandovery) mudrock from central Wales. SHRIMP analyses of monazite nodules from the same horizon are consistent with this, and additionally demonstrate concordance of the U–Pb and Th–Pb systems. These results open the door to providing robust dates for a phase of burial-related diagenesis which, in Wales, seems approximately coincident with, and perhaps was related to, hydrocarbon expulsion.",

keywords = "palaeozoic, Welsh Basin, oil window, monazite, RARE-EARTH ELEMENTS, U-PB, COLLOIDAL PARTICLES, NORTH WALES, WELSH BASIN, FRACTIONATION, METAMORPHISM, ASSEMBLAGES, CARBONATES, URANIUM",

author = "Evans, {J. A.} and Zalasiewicz, {J. A.} and B. Rasmussen and I. Fletcher and Pearce, {Nicholas J. G.}",

note = "Evans, J. A., Zalasiewicz, J. A., Fletcher, I., Rasmussen, B., Pearce, N. J. G. (2002). Dating diagenetic monazite in mudrocks: constraining the oil window?. Journal of the Geological Society, 519 (6), 619-622.",

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doi = "10.1144/0016-764902-066",

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AU - Evans, J. A.

AU - Zalasiewicz, J. A.

AU - Rasmussen, B.

AU - Fletcher, I.

AU - Pearce, Nicholas J. G.

N1 - Evans, J. A., Zalasiewicz, J. A., Fletcher, I., Rasmussen, B., Pearce, N. J. G. (2002). Dating diagenetic monazite in mudrocks: constraining the oil window?. Journal of the Geological Society, 519 (6), 619-622.

PY - 2002/12/1

Y1 - 2002/12/1

N2 - Authigenic monazite nodules, increasingly recognized in Pre-Mesozoic mudrock successions, provide a means for dating diagenesis by exploiting trace uranium within the monazite structure. But, dating is difficult in practice because of zonation and abundant host rock inclusions. We report here a refined technique that has yielded a date of 419 ± 14 Ma 2σ MSWD = 1.2 for a 17-point Pb–Pb regression age from a Telychian (Silurian: late Llandovery) mudrock from central Wales. SHRIMP analyses of monazite nodules from the same horizon are consistent with this, and additionally demonstrate concordance of the U–Pb and Th–Pb systems. These results open the door to providing robust dates for a phase of burial-related diagenesis which, in Wales, seems approximately coincident with, and perhaps was related to, hydrocarbon expulsion.

AB - Authigenic monazite nodules, increasingly recognized in Pre-Mesozoic mudrock successions, provide a means for dating diagenesis by exploiting trace uranium within the monazite structure. But, dating is difficult in practice because of zonation and abundant host rock inclusions. We report here a refined technique that has yielded a date of 419 ± 14 Ma 2σ MSWD = 1.2 for a 17-point Pb–Pb regression age from a Telychian (Silurian: late Llandovery) mudrock from central Wales. SHRIMP analyses of monazite nodules from the same horizon are consistent with this, and additionally demonstrate concordance of the U–Pb and Th–Pb systems. These results open the door to providing robust dates for a phase of burial-related diagenesis which, in Wales, seems approximately coincident with, and perhaps was related to, hydrocarbon expulsion.

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KW - RARE-EARTH ELEMENTS

KW - U-PB

KW - COLLOIDAL PARTICLES

KW - NORTH WALES

KW - WELSH BASIN

KW - FRACTIONATION

KW - METAMORPHISM

KW - ASSEMBLAGES

KW - CARBONATES

KW - URANIUM

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DO - 10.1144/0016-764902-066

M3 - Article

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VL - 159

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EP - 622

JO - Journal of the Geological Society

JF - Journal of the Geological Society

ER -

Dating diagenetic monazite in mudrocks: Constraining the oil window?

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Keywords

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