Calvin Mako

I am a PhD candidate working with Dr. Rick Law and Dr. Mark Caddick. My primary research investigates how the advection of heat by thrust nappes can influence metamorphism in an orogenic belt. I am using monazite, xenotime and titanite geochronology to construct a detailed thermal and structural history of the Scandian orogenic wedge in Scotland. Another facet of my research explores the importance of mechanically generated heat in metamorphic systems. I have constructed numerical models that employ a temperature dependent rheology to predict how much heat a shear zone might produce for a wide range of parameters. I am also studying the metamorphic evolution of central coastal Maine using thermodynamic modeling. The interrelationships between deformation and metamorphism at a variety of scales is a common thread that runs through most of my work.


  Thermal Evolution of Northern Scotland

  Numerical Models of Shear Heating

Calvin:    CV   email

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Publications

Mako, C.A., Williams, M.L., Karlstrom, K.E., Doe, M.F., Holland, M.E., Powicki, D., Gehrels, G., Pecha, M., 2015. Polyphase Proterozoic deformation in the Four Peaks area, central Arizona with relevance for the Mazatzal and Picuris Orogenies. Geosphere, v. 11, no. 6, p. 1-22.

Mako, C.A., Gerbi, C., 2012. Heterogeneous Deformation of Gabbroic Rocks, in Proceedings of the 25th Annual Keck Research Symposium in Geology.

Selected Conference Abstracts

Mako, C.A., Law, R.D., Mazza, S.E., Ashley, K.T., Thigpen, J.R., Cottle, J., Kylander-Clark, A., 2017. Monazite and titanite constraints on the Precambrian metamorphic evolution of the NW highlands terrane, Scotland. GSA Abs. with Progs. Vol. 49, No. 6. To Be Presented at 2017 National Meeting.

Mako, C.A., Caddick, M.J., 2017. Magnitudes of Shear Heating in Metamorphic Systems With Temperature Dependent Rheology. To Be Presented at 2017 AGU Meeting.

Law, R.D., Mazza, S., Thigpen, R., Mako, C., Ashley, K., Krabbendam, M. 2017. Shear senses and deformation temperatures indicated by quartz c-axis fabrics and microstructures … northern Scotland. 21st International Conference on Deformation, Rheology and Tectonics. Inverness, Scotland.

Mako, C.A., Caddick, M., Law, R.D., 2017. Petrology and Monazite Geochronology of the Scarboro Fm., Jefferson, Maine. GSA Abs. Progs. Vol. 49, No. 7.

Mako, C.A., Law, R.D., Cottle, J., Thigpen, J.R., Ashley, K.T., 2016. Monazite-xenotime thermometry constraints on the metamorphic evolution of the Scandian nappe stack, NW Highlands Terrane, Scotland. GSA Abs. Progs. Vol. 48, No. 7.

Thigpen, J.R., Ashley, K.T., Law, R.D., Mako, C.A., 2016. Influence of thrust-related advection and mass transfer on metamorphic heating rates in orogens. Vol. 48, No. 7.

Williams, M.L., Karlstrom, K.E., Mako, C.A., Holland, M.E., 2016. The nature of the mazatzal orogeny in southwestern N. America: new data and persistent questions. GSA Abs. Progs., Vol. 48, No. 7.

Mako, C.A., Law, R.D., Thigpen, J.R., Ashley, K.T., Jercinovic, M.J., Williams, M.L., 2016. Timing of garnet breakdown using monazite geochronology in the Scandian orogenic wedge, NW Scotland (Poster). GSA Abs. Progs. Vol. 48, No. 2.

Mako, C.A., Williams, M.L., Doe, M.F., Karlstrom, K.E., 2013. Timing of Deformation at Four Peaks, central Arizona. GSA Abstracts with Programs. Vol. 45, No. 7, p. 461.

Mako, C., Markley, M., Gerbi, C., 2012. Heterogeneous Deformation of Gabbroic Rocks in the CMBbtz, Grenville Prov., CA. GSA Abs. with Progs. Vol. 44, No. 2, pg. 100.

Thermal Evolution of Northern Scotland

Northern Scotland hosts a well exposed and historically important midcrustal nappe stack with a relatively simple structural and metamorphic record. This makes it an ideal place to study how hot overthrusts can affect footwall metamorphism. Geochronology of a variety of petrologically useful minerals allows us to reconstruct the heating and cooling history of various thrust sheets and helps us to understand the importance of thrust mediated advection of heat. Thrust faulting may fundamentally control the patterns of metamorphism in this area and may even produce very rapid heating and cooling.

Specific temperature-time constraints can be obtained from monazite-xenotime thermometry coupled with U-Pb geochronology. The graph above shows the temperature-time evolution of the Naver nappe in the orogenic hinterland (red). Preliminary data from the Moine nappe (blue) suggests that these thrust sheets at least share a common cooling history.

The above Tera-Wasserburg diagram shows two different age populations of titanite from the Naver nappe that have distinctly different Fe contents. High Fe rims often occur as discontinuous rims on lower Fe titanite (backscatter electron image inset). Titanite growth is associated with the Grampian (475-465 Ma) and Scandian (440-425 Ma) phases of orogenesis. Both of these titanite populations have high Zr contents, indicating temperatures greater than 700C. The fact that both of these age populations are preserved through high temperature metamorphism suggests that heating and cooling may have been rapid.

Numerical Models of Shear Heating

When rocks deform and flow, they produce heat. It is often thought that temperature changes due to shear heating can be significant, but temperature changes are highly dependent on the type of rock, how fast the deformation is, and the duration of deformation. Furthermore, as rocks get hotter, they also get weaker and produce less shear heating (a negative feedback). I have constructed a numerical model that takes all of these factors into account, including progressive thermal softening. The purpose of these models is to provide results that can be applied to natural shear zones, where the conditions of deformation vary widely. Field-based studies will be able to use these results to understand how much temperature change due to deformation could have occurred for specific shear zones and metamorphic systems.

(Above): This figure shows the rates of heat generation produced by stresses and strain rates determined from natural samples (stress compilation from Behr and Platt, 2011). I have calculated strain rates from the flow laws of Hirth et al. 2001 (black circles) and Platt and Behr, 2011 (open squares). The magnitudes of shear heating in natural systems is expected to exceed heat generated by radiogenic decay (red shading), often by orders of magnitude. (Right): Numerical modeling results show that shear heating can exceed 100-200C in some cases. Each panel is calculated for a different initial temperature and background plate velocity and covers a range of shear zone widths and durations of deformation. Black lines indicate temperature and grey lines indicate shear stresses.