ferroan dolomite

ferroan dolomite

[′fer·ə·wən ′dōl‚mīt]
(mineralogy)
A species of ankerite having less than 20% of the manganese positions occupied by iron.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Different types of cements have been recognized within Chichali and Lumshiwal formations which included calcite cement, quartz overgrowths, ferroan dolomite, iron oxide cement and glauconitic cement (Fig.
A late diagenetic stage occurred at a mesogenetic deep-burial depth with carbonate cements appearing as ferroan calcite and ferroan dolomite replacing framework grains and precipitating in intergranular pores.
Other potential minerals affecting the MS of the studied strata are ferriferous glauconite, iron ooids and ferroan dolomite. Glauconite grains (up to ca 200 pm in diameter) are abundant in the Saka and Lahepere members of the Volkhov Stage.
Goldsmith (1959) notes that ankerite is really a ferroan dolomite because no ordering occurs, as verified by the absence of superlattice reflections in XRD patterns.
These are an early low-temperature dolomite, a regional replacive dolomite, black matrix breccia and a hydrothermal ferroan dolomite.
The calcite, hematite, smectite, ferroan dolomite and glauconite occured as cement in the coarse grained lithofacies of the Chichali Formation, thereby reducing the porosity, however, grain fracture porosity, and dolomitization, intergranular and dissolution porosity resulted in increase in the porosity.
Semiquantitative EDS microprobe analysis shows this dolomite to be enriched in iron, and is thus a ferroan dolomite. While most crystals are translucent to opaque and pale yellow-brown in color, some may appear nearly colorless and pseudo-octahedral in habit, due to nearly equal development of rhomb and pinacoid faces.
Two diagenetic stages of carbonate cement are recognized according to petrographic and textural relationships and elemental and stable isotopic composition: the early diagenetic stage in shallow depth, represented by pore-filling and grain-replacing calcite and dolomite, and the late mesogenetic deep burial diagenetic stage, represented by ferroan calcite and ferroan dolomite replacing framework grains and precipitating in intergranular pores.
The XRD, SEM and EDS data revealed that hematite, illite, goethite and ferroan dolomite cement filled the intergranular pores in the Chichali Formation.
Minor diagenetic phases (e.g., ferroan dolomite) are not depicted in this study because of leanly abundant through the Paleogene medium-deep intervals.