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Timothy Latour

Associate Professor(retired)

Ph.D., University of Western Ontario, 1979


Metamorphic Petrology


In recent years my research interests have centered on study of the metamorphic history of the western Blue Ridge of the southern Appalachians. I have focused, in particular, on the Murphy Marble Belt which has been a controversial terrain for many years. My most recent contribution to this area has been to show that the southern Murphy Marble Belt was probably involved in a major thrusting episode, the evidence for which has been recorded in the rocks in the form of a separate and distinct metamorphic-deformational mineral assemblage. This contrasts markedly with the relatively simple metamorphic-deformational history recorded in the northern part of the belt.

I have also been investigating the bulk geochemistry of the schist hosting the marble in the southern Murphy Marble Belt, with the idea that the protoliths may not have been passive-margin shale deposits, but rather volcanic and volcanosedimentary rocks subjected to hydrothermal modification prior to metamorphism. A masters student, Tonya Edwards, has recently completed a nice thesis on this. Her results suggest the probable contribution of volcanic material, but the “smoking gun” has not yet been found. There are additional rock types in the area that have not yet been investigated within this context, and would make another interesting thesis for a masters student.

Along the same general lines, the most recent interest of mine involves the nature of geochemical sorting that accompanies mechanical sorting of sediments. This has a bearing on the interpretation of protoliths of metasedimentary rocks. Ideally, one might be able to tell what the protolith was, exclusively from the bulk geochemistry. Such a tool would be important because many metasediments no longer possess any characteristics to allow for confident interpretation of the protolith. To approach the problem from the fundamentals, the geochemistry of different kinds of sedimentary rocks needs to be studied. I have begun the investigation by looking first at a set of moderately sorted fluvial sedimentary rocks, the Cretaceous-age Kooetnai formation of western Montana. A recently graduated masters student, Paula Cumming, studied the Kootenai geochemistry for her thesis, and was able to demonstrate a clear correlation between the degree of mechanical sorting and the degree of chemical sorting that was consistent with field identification of rock types. The next stage will be to study a suite of rocks that are respectively very well sorted and very poorly sorted. Field areas for these case studies have been partially identified and would be excellent for masters study for one or two students.

I continue to keep a hand in studies of mylonitic rocks and shear zones. My primary involvement is as a lesser player in studies of the implacement of some Iranian ophiolites.