243 Geochemistry (Posters)

Wednesday, 12 October 2011
9:00 AM - 6:00 PM
Hall C

POSSIBLE SOURCES FOR NICKEL AND CHROMIUM IN THE MIDDLE PART OF THE FILLMORE FORMATION IN WEST-CENTRAL UTAH

Paper number: 243-14
Program: Technical Sessions
Time: 9:00 AM – 6:00 PM

Authors

Abstract

Nickel and chromium are not commonly found in carbonate or mixed carbonate depositional environments. All lithologies from a 100-meter section in the middle part of the Lower Ordovician Fillmore Formation at a single locality, the “Pyramid Section”, contain anomalous levels of nickel and chromium. Preliminary data has also shown that there is significantly more nickel in the matrix of two FPCs (range of 0.22 – 0.24 ppm) from the pyramid section than found in the other lithologies at that section (0.05 – 0.10 ppm). However, at a separate locality, “Section C”, in the lower part of the Fillmore Formation neither nickel nor chromium were detected in any lithology. This suggests that the nickel and chromium came from a source that was either spatially or temporally restricted. Two questions arose from these findings. One, what is the source of the nickel and chromium? Two, is there more than one source for nickel in the flat-pebble conglomerates (FPCs) of this section?

The nickel and other trace element anomalies were initially discovered using XRF, and subsequently confirmed with inductively coupled plasma –atomic emission spectrometry (ICP-AES). Possible sources of these elements include 1) Meteorite impact during middle Fillmore time, 2) hydrothermal vents at the time of deposition of the middle part of the Fillmore Formation, or 3) the granitic intrusion in the Notch Peak Formation.

The concentration of nickel in two of the flat-pebble conglomerates might support the hypothesis that these beds are event deposits resulting from meteorite impact, but petrographic analysis of thin sections did not reveal any evidence to confirm meteorite impact as a possible source, such as spherules. A hydrothermal vent generally does not contain that amount of energy and movement of elements is localized. A Jurassic intrusion, the Notch Peak Stock, is closer to the Pyramid Section than it is to Section C. The most likely source is the granitic intrusion. This provided enough time and energy to move nickel and chromium through the Pyramid Section.