Skip to main content

Free Content Precipitation and flocculation of spherical nano-silica in North Sea chalk

Download Article:
 Download
(PDF 340.7880859375 kb)
 

Abstract:

In the Maastrichtian-Danian chalk in the North Sea, discrete intervals, appearing as normal white chalk, contain up to 60% α-quartz <2 m in size. Atomic force microscopy (AFM) reveals that the particles are of nm size, appearing as spherical particles and aggregates. Similar particles consisting of opal-CT were found in surface exposures of chalk in Denmark. Two new abiogenic pathways of silica formation in chalk are proposed. The first model proposes that SiO2 nano-size particles and aggregates precipitated and flocculated in the free-water phase as opal and were diagenetically transformed from opal-CT at low temperature to α-quartz at elevated temperature. In the second model, the dominance of radiolarians in the deep-water environment of the North Sea resulted in low dissolution supply with subsequent precipitation and flocculation of nano-size a-quartz particles. In the shallower water of the shelf environment of the present onshore chalk, the abundance of sponges and their dissolution supplied enough Si to precipitate opal-CT in the free-water phase.

Document Type: Research Article

DOI: https://doi.org/10.1180/000985500546567

Publication date: 2000-03-01

More about this publication?
  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
UA-1313315-23
Cookie Policy
X
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more