|Title||Dolomite fluorescence color variation, chemical or thermal effect, LA-ICP-MS evidence|
|Author||Ardakani, O H; Sanei, H; Jackson, S E; Yang, Z; Al-Aasm, I S|
|Source||Goldschmidt Yokohama 2016, conference abstracts; 2016 p. 100|
|Alt Series||Earth Sciences Sector, Contribution Series 20150461|
|Meeting||Goldschmidt Yokohama 2016; Yokohama; JP; June 26 - July 1, 2016|
|Media||paper; on-line; digital|
|NTS||21L; 31H; 31I|
|Lat/Long WENS|| -75.0000 -71.0000 47.2500 45.0000|
|Subjects||geochemistry; fossil fuels; petroleum resources; hydrocarbons; gas; spectroscopy; spectroscopic analyses; mass spectrometer analysis; sedimentary rocks; shales; fluorescence analyses; thermal
maturation; vitrinite reflectance; temperature; major element geochemistry; minor element geochemistry; trace element geochemistry; rare earths geochemistry; magnesium; iron; Utica Shale; dolomite fluorescence; crystal zonation; rare earth elements;
light rare earth elements; Phanerozoic; Paleozoic; Ordovician|
|Program||Shale Reservoir Characterization, Geoscience for New Energy Supply (GNES)|
|Links||Abstract - Résumé|
|Links||Online - En ligne (Full abstract volume
/ Volume complet des résumés, PDF, 96 MB)|
|Abstract||This study presents preliminary results of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis of scattered dolomite crystals in Upper Ordovician Utica Shale from southern
Québec to investigate the cause of dolomite fluorescence zonation in samples of different thermal maturity. Utica Shale dolomite crystals show zonation under ultraviolet (UV) light, with a shift from higher red/green quotient (R/G Q) in crystal cores
to lower R/G Q in the crystal rims. In addition, the R/G Q shows an increase with thermal|
maturity of the shale, where the cores of dolomite crystals of over-mature samples with equivalent vitrinite reflectance (VRoeqv.) > 2% tend to have higher
R/G Q in comparison to mature samples with VRoeqv. ~ 1% (red shift). These two parameters show a strong positive correlation that suggests that dolomite fluorescence color variation is possibly controlled by temperature .
shows that major and minor (Ca, Fe, Mn, Na), trace (Sr, Zn, Cu) and rare earth (La, Ce, Nd, Sm, Gd, Dy, Er, Yb) elements generally show consistently higher concentrations in crystal rims than cores, while the Mg concentration is consistently higher
in the crystal cores (~ 10%) than rims (~ 7%). Concentrations of Fe show a decreasing trend from mature to over-mature samples, especially
in the crystal rims. Over-mature samples have relatively higher concentrations of LREE (La, Ce, Nd, Sm) in
the crystal rim, while the other elements do not show any trend with thermal maturity. Consistently lower Mg concentrations in the crystal rims in comparison to the cores suggest Mg depletion of dolomitizing fluids during dolomite precipitation.
Depletion of Mg, one of the major constituents of dolomite, likely causes increases in the concentrations of other elements. However, variations in concentration of Fe and LREE with thermal maturity suggest that temperature can possibly have an
overarching effect on chemistry of dolomite that ultimately controls the crystal zonation.
 Haeri-Ardakani & Sanei (2015) IJCG 135 165-171.
|Summary||(Plain Language Summary, not published)|
This study presents preliminary results of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis of scattered dolomite
crystals in Upper Ordovician Utica Shale from southern Québec to investigate the cause of dolomite fluorescence zonation in samples of different thermal maturity.