Project

Back to overview

Trace elements in authigenic quartz

English title Trace elements in authigenic quartz
Applicant Ramseyer Karl
Number 107482
Funding scheme Project funding (Div. I-III)
Research institution Institut für Geologie Universität Bern
Institution of higher education University of Berne - BE
Main discipline Geology
Start/End 01.11.2005 - 31.10.2008
Approved amount 153'159.00
Show all

Keywords (5)

Trace Elements; Syntaxial Quartz; Diagenesis; SIMS; Pore Water Chemistry

Lay Summary (English)

Lead
Lay summary
Authigenic homoachsial quartz cement is the most abundant permanently pore-occluding diagenetic phase in siliciclastic rocks. There exists reasonable agreement on the most important silica sources for quartz cementation under burial conditions (e.g., >70°C), and the precipitation rates are fairly established, based on empirical data (e.g., combination of fluid inclusion data with burial temperature modeling, volume of quartz cement and free surface on detrital quartz grains), but neither the controlling factors of trace elemental uptake into the quartz lattice nor their influence on the growth dynamics (e.g., precipitation rate) are known.
The aim of this project is a continuation of the research on controlling mechanisms of quartz precipitation in siliciclastic sediments. Focussing points are the causes of trace element uptake and their significance for quartz precipitation under diagenetic conditions.
In a first part the research will be based on quantitative SIMS trace element traverses from syntaxial quartz cement in samples from the siliciclastic Haushi Group, Sultanate of Oman, which cover the present-day depth range from surface outcrop to almost 5000 m depth. Previous studies on these samples using fluid inclusion microthermometry and stable isotope analyses combined with burial-thermal modeling, unraveled the timing of quartz precipitation, its multi-source origin and cogenetic mineral reactions as well as the compositional evolution of the pore fluid during quartz cementation. Hence, the trace element compositional evolution obtained in the proposed study shall be directly related to the known physico-chemical conditions during quartz precipitation and their controlling factors shall be deduced from these relations.
Knowledge of these field-based relations between trace element incorporation and physico-chemical parameters, plus results of thermodynamic calculations of the pore water chemistry (constrained by the observed cogenetic mineral reactions, e.g. K-feldspar dissolution and kaolinite precipitation, smectite to illite reaction, and kaolinite to illite transformation) shall be used to compare with the measured trace element variations.
The findings of this study will have an important impact for understanding and measuring trace elements in quartz precipitated from an aqueous solution. It will also be the first time that hydrogen is quantified in quartz at a micron level together with other trace elements. The results will clearly document the influence of the charge compensating monovalent ions for the uptake of trivalent ions and show if trace elements are diagnostic for the source of silica, e.g., pressure solution vs.alumosilicate reactions.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Name Institute

Associated projects

Number Title Start Funding scheme
58755 Quartz precipitation in siliciclastic rocks 01.04.2001 Project funding (Div. I-III)
121742 Trace elements in authigenic quartz 01.11.2008 Project funding (Div. I-III)

-