Primary magnesium, stable isotopic, and trace elemental composition of late Devonian marine calcite neptunian dike cement from Canning basin, Australia

Conference · Thu May 01 04:00:00 EDT 1986 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:5165622

Opdyke, B N; Wilkinson, B H; Lohmann, K C; Given, R K

Numerous recent studies have documented secular variations in the isotopic (/sup 18/O, /sup 13/C, /sup 34/S, Sr/sup 87/86/) composition of Phanerozoic marine carbonate and first-order changes in the position of global sea level. These changes, in combination with suggested relations of sea floor spreading rates and ridge thermal histories with the composition of sea water, strongly implicate changes in other oceanic chemical parameters through the Phanerozoic. In order to evaluate secular trends in the initial trace element composition of inorganic marine carbonate precipitates, magnesium, manganese, iron, and stable isotopic compositions were determined for marine calcite cement from the Upper Devonian reef complex in the Canning basin of Western Australia. These cements comprise alternating layers of inclusion-rich fibrous calcite crystals and clear inclusions-free equant crystals. In comparison to fibrous calcites, inclusions-free cement is significantly enriched in /sup 18/O (-3.7 per thousand), /sup 13/C (+2.8 per thousand), and Mg (6 mole %), and is depleted in Fe and Mn. The isotopic and trace elemental composition of fibrous layers reflects increased alternation of inclusions-rich cement with the subsequent incorporation of manganese- and iron-enriched and oxygen- and carbon-depleted diagenetic intergrowth. Manganese plus iron concentrations vary with depleted /sup 13/C and /sup 18/O values, indicating a coupling of stable-isotope and trace-element chemistry during diagenesis. Extrapolation of these trends toward the marine end-member composition yields values identical with those of inclusions-free cement, indicating that the clear calcite yields primary trace-element and stable-isotopic compositions for latest Devonian marine calcite cements.

• Research Organization: Univ. of Michigan, Ann Arbor
• OSTI ID: 5165622
• Report Number(s): CONF-860624-
• Conference Information: Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Journal Volume: 70:5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
ALKALINE EARTH METAL COMPOUNDS
ALKALINE EARTH METALS
AUSTRALASIA
AUSTRALIA
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CHEMISTRY
DIAGENESIS
DOLOMITE
ELEMENTS
GEOCHEMISTRY
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
MAGNESIUM
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MATURATION
METALS
MINERALS
OXYGEN COMPOUNDS
RESERVOIR ROCK
ROCKS
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
TRACE AMOUNTS