TY - CHAP
T1 - Chapter 10 Alteration of Opaque Heavy Minerals as a Reflection of the Geochemical Conditions in Depositional and Diagenetic Environments
AU - Weibel, Rikke
AU - Friis, Henrik
PY - 2007
Y1 - 2007
N2 - Detrital opaque heavy minerals are minor but common constituents of most detrital sediments. It is sometimes possible to map the diagenetic paths of those opaques that are readily altered through changing oxidising and reducing geochemical environments, both depositional, post-depositional and diagenetic. The alteration of opaque heavy minerals from different depositional and diagenetic environments, reflecting various geochemical regimes, is reviewed and evaluated. The investigated deposits span from Triassic red beds (Skagerrak and Bunter Sandstone Formations) with early oxidising conditions (including local reduction spots representing early reducing conditions) through weakly reducing conditions of the Miocene Odderup Formation to the strongly reducing environment of the Gassum Formation, where abundant iron and organic matter, and thus related sulphate reduction, have influenced the alteration products. Extreme sulphur-dominated local environments are represented by Holocene carbonate-cemented sandstone pillars. When successive phases of oxidation and reduction occur, the resulting assemblage of primary detrital opaque heavy minerals and their alteration products converge; a detailed study can sometimes reveal the sequence of events. A comparison of the alteration sequence of detrital Fe-Ti oxides, together with identification of authigenic opaques, from red and drab parts of the succession in Triassic red beds (Skagerrak and Bunter Sandstone Formations), has enabled us to distinguish primarily oxidised horizons, primarily reduced areas, secondarily reduced originally oxidised areas, and secondarily oxidised originally reduced areas.
AB - Detrital opaque heavy minerals are minor but common constituents of most detrital sediments. It is sometimes possible to map the diagenetic paths of those opaques that are readily altered through changing oxidising and reducing geochemical environments, both depositional, post-depositional and diagenetic. The alteration of opaque heavy minerals from different depositional and diagenetic environments, reflecting various geochemical regimes, is reviewed and evaluated. The investigated deposits span from Triassic red beds (Skagerrak and Bunter Sandstone Formations) with early oxidising conditions (including local reduction spots representing early reducing conditions) through weakly reducing conditions of the Miocene Odderup Formation to the strongly reducing environment of the Gassum Formation, where abundant iron and organic matter, and thus related sulphate reduction, have influenced the alteration products. Extreme sulphur-dominated local environments are represented by Holocene carbonate-cemented sandstone pillars. When successive phases of oxidation and reduction occur, the resulting assemblage of primary detrital opaque heavy minerals and their alteration products converge; a detailed study can sometimes reveal the sequence of events. A comparison of the alteration sequence of detrital Fe-Ti oxides, together with identification of authigenic opaques, from red and drab parts of the succession in Triassic red beds (Skagerrak and Bunter Sandstone Formations), has enabled us to distinguish primarily oxidised horizons, primarily reduced areas, secondarily reduced originally oxidised areas, and secondarily oxidised originally reduced areas.
KW - alteration
KW - diagenetic environment.
KW - Fe-Ti oxides
KW - geochemical conditions
KW - hematite
KW - ilmenite
KW - magnetite
KW - opaque heavy minerals
KW - oxidising conditions
KW - reducing conditions
KW - titanomagnetite
KW - Heavy minerals
KW - Heavy mineral assemblage
KW - Opaque minerals
KW - Geochemical redox conditions
UR - http://www.scopus.com/inward/record.url?scp=34249077591&partnerID=8YFLogxK
U2 - 10.1016/S0070-4571(07)58010-6
DO - 10.1016/S0070-4571(07)58010-6
M3 - Chapter in book
AN - SCOPUS:34249077591
SN - 9780444517531
T3 - Developments in Sedimentology
SP - 277
EP - 303
BT - Heavy Minerals in Use
A2 - Mange, Maria
A2 - Wright, David
ER -