Research

Much of my research has centered upon the evolution of magmatic systems and their interaction with continental crust. This has included work in volcanic fields associated with the southern portion of the late-Tertiary Basin and Range extensional province in northern and central Mexico; mid-Tertiary subduction-related magmatism in the Sierra Madre Occidental in northwestern Mexico; and late-Tertiary intraplate, post-collisional magmatism in western New Guinea.

Hoya de Alvarez: a Pleistocene maar in the Valle de Santiago volcanic field, Guanajuato, where earlier calc-alkaline subduction-related volcanism has changed over to mafic-alkalic volcanism associated with maar complexes and late lava flows.

In the Basin and Range province in central and southern Mexico, where Dr. Housh has been working with J.F. Luhr and J.J. Aranda-Gómez, they have studied several mafic alkali volcanic fields. Some of the questions they are working to address include: What were the relative influences of interaction between asthenospheric and lithospheric mantle and continental crust in the evolution of the magmas erupted in these fields? Is a progression in time from lithospheric-dominated magmas to magmas generated seen in the asthenosphere as has been postulated for the SW United States? Are there differences in the evolution of magmas within small volcanic fields versus large volcanic fields? What role did extensional faulting play in the observed distribution of volcanism? Why are there very similar volcanic fields outside of the area of extension associated with the southern part of the Basin and Range extensional province?

 

Cascada de Basaseachic; a waterfall with a drop of 312 m in intracaldera facies tuff of the ca. 30 Ma Ocampo caldera, western Chihuahua.

I am also involved in radiogenic isotope and geochemical studies of mid-Tertiary subduction-related volcanic rocks in the Sierra Madre Occidental with Fred McDowell. We have found systematic regional variations in the radiogenic isotopes of intermediate and silicic magmas in northwestern Mexico. Two of the questions they have sought to address in this study are: Can these variations be related to changes in the nature of the subsurface crystalline basement within the region (e.g. Laurentia and accreted terranes such as the Ouachita, Guerrero, etc)? Secondly, what do these variations imply about the role of crustal contamination in the formation of intermediate and felsic volcanic rocks? We have also recently begun to characterize and date crustal xenoliths found within a caldera in the Sierra Madre Occidental in order to better determine the nature of the basement beneath that area.
 

The Grasberg porphyry Cu-Au deposit, located at the crest Sudirman Mountains, Papua, Indonesia is one of the largest copper and gold mines in the world.  Rare equitorial glaciers can be seen along the summit of the mountains to the east of the Grasberg mine (Photo: www.eol.jsc.gov/EarthObservatory/Grasberg-Mine_Indonesia.htm, public domain).

Another magmatic suite I am studying are post-collisional, intraplate, strongly alkalic volcanic and plutonic rocks from the Grasberg mining district and the Central Ranges in the western part of the island of New Guinea. Highly enriched isotopic compositions indicative of the presence of ancient lithosphere have been found beneath the western part of the island of New Guinea. A key question is just how much of the distinctive isotopic signature can be attributed to derivation from an ancient, enriched lithospheric mantle source versus crustal level contamination? Secondly, what role did this enrichment play in the formation of the giant Grasberg ore deposits?

Mine tailings in the Tri-State mining district, west of Prosperity, Jasper Co., Missouri. The Tri-State district covers portions of southwestern Missouri, northeastern Oklahoma and southeastern Kansas and contained more than 4000 mines. For one hundred years (1850-1950) the Tri-State district produced 50 percent of the zinc and 10 percent of the lead in the United States.

More recently I have also begun to develop the analysis protocols for Fe, Cu, Zn and Sb isotopes on the IsoProbe. The study of these isotope systems has recently become possible with the development of new analytical instrumentation. These isotope systems are being studied because of the information they could potentially provide about equilibrium, kinetic, redox and biogenic processes involved in the formation of ore deposits and lower temperature hydrologic systems.  Some current projects include Cu isotope studies of mineralization from the Grasberg Cu-Au porphyry, volcanogenic massive sulfide deposits in the eastern Pontides of northeastern Turkey, and Mississippi valley-type mineralization in the Tri-State mining district of Missouri, Oklahoma and Kansas.