Composition of brines in halite‐hosted fluid inclusions in the Upper Ordovician, Canning Basin, Western Australia: new data on seawater chemistry

Abstract

Analyses of primary and early diagenetic fluid inclusions in the halite from the Late Ordovician Mallowa Salt, Canning Basin, Western Australia indicate a Ca-rich composition and high concentration of parent brines in the basin which were close to sylvite and carnallite precipitation. The salt-bearing series in the sampled interval was overheated up to 62°C. The recorded differences in gas compositions result from the input of several gas sources including dispersed organic matter in the salt series and hydrocarbon deposits in the underlying rocks. The high concentration of the brines in fluid inclusions does not allow quantitative reconstruction of the chemical composition of Late Ordovician parent seawater. Using the information from Early Cambrian and Late Silurian basins as a proxy, however, the new data indicate that Late Ordovician seawater was undoubtedly Ca-rich and, in comparison with modern seawater, had a similar K content, considerably lower Mg content (c. 30%), approximately three times the Ca content and one-third the SO 4 content.

High‐density nitrogen inclusions in barite from a giant siderite vein: implications for Alpine evolution of the Variscan basement of Western Carpathians, Slovakia

“…At diagenetic temperatures, the fixed ammonium can be released by 40 K radiolysis (Grishina et al ., 1998). The anchimetamorphic sedimentary cover overlying the Gemeric basement appears to be a good candidate for the nitrogen‐source rock, from which the ammonium could have been liberated during dissolution of evaporites (Pironon et al ., 1995; Petrychenko et al ., 2005; Kovalevych et al ., 2006) or deammination of organic matter. Furthermore, the ammonium could also be produced in basement rocks by reaction of biotite and plagioclase with percolating brines (Darimont et al, 1988).…”

Seawater Chemistry and Early Carbonate Biomineralization

“…These indicate that the Mg 2+ /Ca 2+ ratio of late Ediacaran seawater favored aragonite precipitation (4, 6), whereas the Mg 2+ /Ca 2+ ratio of Tommotian/ Atdabanian through Toyonian seawater (4, 6, 7), as well as that of late Ordovician seawater (4,8), favored calcite precipitation ( Fig. 1B and table S2).…”

Calculation of salt basin depth using fluid inclusions in halite from the Ordovician Ordos Basin in China

“…Three types of in clu sion are dis tin guished by gas com po nents: one with sub stan tial ni tro gen (N 2 >CO 2 >CH 4 ), one with sub stan tial meth ane (CH 4 >N 2 >CO 2 ), and one with nitro gen-meth ane (N 2 ³ CH 4 >CO 2 ) (Litvinyuk, 2007). The methane con tent pre vails over ni tro gen in the fluid in clu sions of halite, as meth ane is drawn from the salt-bear ing lay ers, rich in organic mat ter (Galamay and Baranenko, 2004;Kovalevych et al, 2006).…”

“…Pre vi ous stud ies on the com po si tion of gas in the brines of pri mary and early diagenetic in clu sions within ha lite dur ing var i ous time pe ri ods of the Phanerozoic (Litvinyuk, 2007;Wiêc³aw et al, 2008), par tic u larly dur ing the Or do vi cian (Kovalevych et al, 2006), show that the sum of N 2 + CH 4 in the in clu sions amounts to >70%, with CO 2 com pris ing 0-23.8% (mean = 7.1%). The hy dro gen data in the gas mix ture are not in for ma tive due to the abil ity of hy dro gen to dif fuse freely through the crys tal struc ture of the min eral.…”