Multi method approach to heavy mineral exploration: Miocene of Denmark

C. Knudsen, T. Rasmussen, D. Frei, R. McLimans, T. Jørgensen, T. Fischer

Publikation: Bidrag til bog/rapport/konferenceproceedingsKonferenceartikel i proceedings

Abstrakt

Ilmenite-bearing paleo-beach deposits were discovered in Jylland, Denmark using a combination of Ground Penetrating Radar (GPR), portable X-ray fluorescence (XMET), bulk XRF analyses, Computer Controlled Scanning Electron Microscopy (CCSEM), and wire line logging. The Miocene-age paleo-beach deposits are located below a thin Quaternary cover in a region of very moderate relief and essentially no outcrop demanding unique approaches in exploration. Initially, an isopach map of the Quaternary is prepared from existing water well data. A geological model for likely occurrence of Miocene paleo-beach deposits is generated and the coincidence of thin Quaternary cover and potential paleo-beach deposits define targets for detailed exploration. The defined targets are traversed with GPR to identify paleo-beach structures which are then used to define a drilling program. This methodology located a paleo-barrier island at the Vorslunde location with more than 10% ilmenite in the sand. During the drilling process, the TiO 2 and heavy mineral contents of the sand were logged every meter with a portable XRF unit (XMET) and subsequently calibrated more accurately by comparison to bulk XRF and CCSEM analyses for selected samples. The bulk XRF data also provided more complete compositional information. Insitu determination of geology, heavy mineral abundance, and corroboration of the XRF logging was done using wire line logs, a combination of spectral gamma and induction conductivity logs. Detailed characteristics (abundance, grain size, shape) and chemical composition of minerals was determined by the GEUS CCSEM methodology (Frei et al, this vol.). The average weight percent TiO 2 for all Ti-minerals is 62%, 60% excluding rutile. That elevated TiO 2 content (≫ ilmenite stoichiometric value, ca. 50 %) indicates that ilmenite experienced an iron-leaching environment The source of the sand deposit was investigated by dating contained zircon. The results show that the likely sources of zircon are in southern Norway and southwestern Sweden with common zircon ages of ca 1100 Ma. and 1500 Ma.

OriginalsprogEngelsk
Titel2005 Heavy Minerals Conference Proceedings, HMC 2005
RedaktørerM. Akser, J. Elder
ForlagSociety for Mining, Metallurgy and Exploration
Sider83-90
Antal sider8
ISBN (Trykt)0873352459, 9780873352451
StatusUdgivet - 2005
BegivenhedHeavy Minerals 2005 - Ponte Vedra, Jacksonville, Florida
Varighed: 16 okt. 200519 okt. 2005

Konference

KonferenceHeavy Minerals 2005
ByPonte Vedra, Jacksonville, Florida
Periode16/10/0519/10/05

Programområde

  • Programområde 4: Mineralske råstoffer

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