English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

This report presents the results of a study of the stable isotopic and chemical composition of secondary carbonate minerals precipitated within basalts at Ocean Drilling Program Sites 707 and 715. At Site 715, the secondary carbonates are all composed of calcite and display a narrow range of carbon and oxygen stable isotope ratios, with values ranging from 2.75%o to 1.95%o PDB and O.27%o to 2.86%o PDB, respectively. Strontium, iron, and manganese values of the samples are generally low. The geochemistry of Site 715 samples indicates that they precipitated from seawater-dominated fluids, at low temperatures, as is typical of secondary carbonates from most Deep Sea Drilling Project sites. In contrast, at Site 707, aragonite, siderite, and manganese-rich calcite occur as secondary carbonates in addition to calcite. The carbon isotopes of the Site 707 carbonates of all rock types are depleted in C. Values range from 2.79%o to 16.43%o PDB. Oxygen isotope values do not show a wide variation, ranging from 1.78%o to 1.17%o. The strontium contents of the samples range from 5200 to 8100 ppm for aragonites, and from 145 to 862 ppm for calcites. Iron and manganese contents are high in calcites and siderites and low in aragonites. Site 707 carbonates precipitated at low temperatures in a fairly closed system, in which basalt-seawater interaction has greatly influenced the chemistry of the pore fluids. The reactions occurring within the system before and in conjunction with secondary carbonate precipitation include oxidation of isotopically light methane, derived from fluids circulating within the basalts, and reduction of substantial amounts of iron and manganese oxides from the basalts.

Geochemistry of Secondary Carbonates in Leg 115 Basalts: Tracers of Basalt/Seawater Interaction