Mathematics – Logic
Scientific paper
Aug 1977
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1977gecoa..41.1041k&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 41, Issue 8, pp.1041-1051
Mathematics
Logic
31
Scientific paper
Evidence from deep-sea sediments supports the following diagenetic maturation sequence: opal-A (siliceous ooze) opal-CT (porcelanite) chalcedony or cryptocrystalline quartz (chert). A solution-redeposition mechanism is involved in the opal-A to opal-CT transformation. Exceptions to the overall maturation sequence are numerous, suggesting that temperature and time are not the only important factors controlling these mineralogical transformations. The rates of the above transformations are strongly affected by the composition of the solution and of the host sediments ; in Mesozoic clayey sediments, opal-CT predominates, while in carbonate sediments quartz is most common. Experiments at 25 and 150°C over a period of one day to six months show that the transformation rate of opal-A to opal-CT is much higher in carbonate than in clay-rich sediments, and that opal-CT lepisphere formation is aided by the precipitation of nuclei with magnesium hydroxide as an important component. The role of carbonate is explained as follows : in carbonate-rich sediments, the dissolution of carbonate provides the necessary alkalinity, and sea water provides the magnesium for the magnesium hydroxide in the nuclei. In contrast, in clay-rich sediments the clay minerals compete with opal-CT formation for the available alkalinity from sea water. As a result, the clays are enriched in Mg, and the rate of opal-CT formation is strongly reduced. This mechanism also bears on the common observation of carbonate replacement by silica.
Gieskes Joris M.
Kastner Michael
Keene J. B.
No associations
LandOfFree
Diagenesis of siliceous oozes--I. Chemical controls on the rate of opal-A to opal-CT transformation--an experimental study does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Diagenesis of siliceous oozes--I. Chemical controls on the rate of opal-A to opal-CT transformation--an experimental study, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Diagenesis of siliceous oozes--I. Chemical controls on the rate of opal-A to opal-CT transformation--an experimental study will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1880486