Research

 

My most recent research endeavor is studying the volcanic rocks -- basalts and silicic lavas and pyroclastics -- in the Goldfield-Superstition mountains, central Arizona. This is an especially meaningful research area for me because I was introduced to this volcanic province located ~30 miles east of Phoenix some decades ago by my graduate advisor at Arizona State University, Dr. M.F. Sheridan, to study as a Masters thesis.  So, it's a thrill to return to the Goldfield-Superstitions after so long but now armed with 40+ years of experience as an igneous petrologist -- first at the University of New Mexico and, for the past 31 years as a Professor of Geology at North Carolina State University.

I want to share some pictures of this desert environment....such a fantastic geologic, biologic, and spiritual experience to hike, collect samples, and map in the Goldfield-Superstitions. But first, pictures of our year-2005 Fall Break field trip class which spent five days in the region, camping and exploring the geology.

Arizona Research and Activities

 

Part of our class sitting on a basalt knob in the Goldfields, a feature shown in one of the photos below.

Here's our group photo on the ASU campus (October 2005)

  

 

         

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Other Reseach Interests and Activities

 

I have been studying gabbroic and ultramafic xenoliths erupted during the postshield stage of volcanism on Mauna Kea volcano, Hawaii.  This is largely a microprobe and petrography endeavor, but has also included whole-rock analyses for major and trace elements, and some Sr, Nd, and Pb isotopes.  Other Hawaiian studies involve lavas and gabbroic xenoliths of Kahoolawe Island, Koolau volcano, Kilauea volcano, and Mauna Loa volcano.

A cinder cone on Mauna Kea shield volcano
that yields a variety of ultramafic and gabbroic xenoliths

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A gabbro xenolith with layering as a small-amplitude fold,
and quartz-bearing "gabbroic" xenolith -- both from Mauna Kea volcano.

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   My Mauna Loa research is an outgrowth of grad student Renee McCarter's thesis project -- a petrologic study of gabbroic lithic fragments 'blown' out of the summit caldera (see pictures below)  Her thesis work (yr 2001-02; published in McCarter et al., 2006) has shown that these gabbroic 'xenoliths' represent a prehistoric lava lake that crystallized at the summit, and it gives us good insight to crystallization dynamics and compositional evolution that occur in magma reservoirs.

Here's a great example of a veined gabbroic xenolith in place at the rim of Mauna Loa summit. The veins are glassy, and have phenocrysts of clinopyroxene and plagioclase (and Fe-Ti oxides); whole-rock compositions are evolved (e.g., approximately 55-59 wt.% SiO2).

Don't step back folks!!   Here's Ron and student Renee at the rim of the caldera on Mauna Loa volcano summit (May 16, 2001; photo by Frank Trusdale)

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Antarctic Studies

Thanks to Dr. Bruce Marsh at Johns Hopkins, I had the opportunity to join a petrology group in Antarctica, January, 2005, for examining and sampling a giant gabbroic sill, the Basement sill. We stayed both at McMurdo Sound Station and in the Dry Valleys, camping (below). My focus was on segregation veins in the sill; see the outcrop picture and a representative thin section (below). Some of the segregation veins are evolved to diorite in composition.

 

Other Studies from over past years

(...say.. is the Washington Monument made of marble?.....)

Studies of continental alkalic basalts in recent years are for Tertiary provinces along the Hungary-Slovakia border (e.g., Nograd province) and in northeastern Brazil. These studies have involved whole-rock major- and trace- element compositions, isotope compositions, and microprobe analyses for mineral compositions.

Mantle xenoliths studies are largely based on those from Tertiary alkalic basalt centers in northeastern Brazil. These are spinel lherzolites and harzburgites that manifest a large range of equilibration temperatures, ~1200oC to 850oC.

Some mineral-specific studies addresscompositions of some not-so-common minerals such as hollandite in Hawaiian basalt, rhabdophane (REE-phosphate) in Hawaiian basalt, and rhoenite in an ankaramite from Columbia seamount (offshore Brazil).

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Last Update: June, 2008