Current Research Projects

Textural analysis of experimental and natural volcanic materials

textural analysis image a) Number density versus equivalent diameter for each of four magnifications. (c) The FOAMS program can choose the best cutoff positions for merging information from each magnification to produce the complete number density curve.

In collaboration with Bruce Houghton, Lucia Gurioli, and Kathy Cashman, Tom Shea is developing tools for quantitative analysis of vesicle textures, with the goal of providing a systematic and rigorous methodology to the volcanological community. More info? Click here.

 

 

 

 

 

 

textural analysis image Plane light photomicrograph of thin section #105 showing regions of interest selected for quantitative analysis of groundmass texture (red boxes). Phenocryst phases are Ca-pyroxene and olivine.

textural analysis image (A) Quantitative relationship between cooling rate and pyroxene texture for two populations of groundmass Ca-pyroxene in the calibration set. (B) Linear trends from experimental data set are overlaid by clinopyroxene populations in MIL03346 as shaded horizontal bars. Because two populations are observed, the maximum calculated cooling rate must be less than 72°C h-1. Vertical stippled bar shows cooling rate range that satisfies texture of both phenocryst rims and microphenocrysts (17.4 – 21.7°C h-1, or ~20°C h-1).

We apply results from an experimental study of constant-rate cooling of Fe-rich basalt to interpretation of the late-stage igneous cooling history of Martian meteorite MIL 03346. We employ the fact that the ratio of crystal-melt surface area to volume typifying morphologically distinct populations of Ca-pyroxene varies as a strong function of cooling rate, and suggest that the range of cooling rates consistent with 3D aspect ratios of both populations in MIL03346 is ~20°C h-1.

Funding: NSF EAR-0449888 and NASA NNG05GL92G

 

 

 

 

 

 

 

 

 

 

 

[ top of this page | return to research page ]