The fission track record of Apennine Front KREEP basalts

Pages (1975)

Citation

Reference

Related Paper

Abstract:

Whitlockite grains in two Apennine Front KREEP soil fragments contain extremely high densities of fission tracks. A new method is described in which particle tracks are examined in an actinide-poor phase bordering an actinide-rich whitlockite phase. This method clearly distinguishes the fission track contributions from other track sources; e.g., Fe-group cosmic rays, spallation recoils, and dislocations. Observed track excesses, when corrected for U- and Th-related fission sources, are 4-20 times greater than the contribution from spontaneous fission of U-238 (based on an age of 4 b.y.), and probably represent a large and variable contribution from the fission of Pu-244. These fragments may have pre-Imbrium ages, underscoring the importance of KREEP as a constituent of the pre-mare lunar crust. Track excesses are not correlated with the U or Th contents of the whitlockite grains. This behavior suggests that Pu fractionates differently from U and Th in lunar igneous KREEP.

Keywords:

Whitlockite

Fission track dating

Topics:

Geological and Geochemical Analysis

Planetary Science and Exploration

Geology and Paleoclimatology Research

Source

Cite

Fission tracks in basin analysis

AAPG Bulletin (1991)

Nancy D. Naeser

Over the last 12 years, fission-track analysis has emerged as a widely used method for tracing the depositional and thermal history of sedimentary basins. The fission tracks found in minerals are zones of intense damage formed by the spontaneous fission of {sup 238}U. Because spontaneous fission takes place at a constant rate, fission tracks can be used to date these minerals. In many studies, fission tracks have established geochronology and correlation in basins, particularly by dating volcanic ash beds in sedimentary sequences. However, major interest in fission tracks in basin analysis centers on their ability to provide information about thermal history. Fission tracks remain relatively stable in most minerals at ambient surface temperatures, but when a mineral is heated the tracks become progressively shorter and ultimately disappear. The temperature range over which this 'annealing' takes place depends on the mineral being analyzed and the duration of heating. Apatite is by far the most commonly used mineral in thermal history studies. One reason for its popularity is that more experimental and empirical data on annealing temperatures are available for apatite than for any other mineral, but what is more important for basin analysis is that apatite annealing temperatures coincide with themore » temperature range of hydrocarbon generation and a number of other low- to moderate-temperature processes in basins. The reduction in mean track length, change in track-length distribution, and reduction in fission-track age that results from annealing can be used to trace, within this critical temperature range, the timing and magnitude of heating and cooling of sedimentary sequences.« less

Fission track dating

Closure temperature

Geochronology

Source

Cite

Citations (0)

The fission track record of Apennine Front KREEP basalts.

Lunar and Planetary Science Conference Proceedings (1975)

E. L. Haines I. D. Hutcheon J. R. Weiss

Whitlockite

Fission track dating

Source