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Title: Occurrence and significance of magnesite in Upper Permian (Guadalupian) Tansill and Yates Formations, Delaware Basin, New Mexico

Journal Article · · AAPG Bulletin (American Association of Petroleum Geologists); (USA)
OSTI ID:6891222
; ;  [1]
  1. Chevron Oil Field Research Co., La Habra, CA (USA)

Magnesite (MgCO{sub 3}) occurs pervasively in a 270-ft (82-m) cored interval of Upper Permian (Guadalupian) shelf deposits from the northern rim of the Delaware basin portion of the Permian basin, New Mexico. In their core example, magnesite is found in tidal flat/lagoon and pisolite shoal dolomites and siltstones of the Tansill and uppermost Yates formations. The interval is overlain by magnesite-bearing anhydrite and a thick halite section of the (Ochoan) Salado Formation. The basinwide extent of magnesite is unknown. Magnesite may have formed either (1) during Ochoan deposition or thereafter, after burial of the Tansill and Yates formations, from dense brines originating from the overlying Salado evaporites; or less likely, (2) syndepositionally with the Tansill and Yates sediments. Preliminary measurements of stable carbon and oxygen isotopes for magnesite yield normal Permian values for {delta}{sup 13}C averaging + 6.84% (PDB) and slightly evaporitic values for {delta}{sup 18}O averaging + 1.04% (PDB); corrected {sup 87}Sr/{sup 86}Sr isotope composition averages 0.70687. Because a high content of associated uranium in the magnesite-rich part of the core causes large gamma-ray deflections similar to those for shale, and because the density of magnesite is close to that of anhydrite, the presence of magnesite could lead to improper evaluation of lithology and porosity from logs and could ultimately result in failure to recognize potential reservoir zones. 14 figs., 1 tab.

OSTI ID:
6891222
Journal Information:
AAPG Bulletin (American Association of Petroleum Geologists); (USA), Vol. 74:2; ISSN 0149-1423
Country of Publication:
United States
Language:
English

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