Physical properties Geos 408/508 Lec 11

What matters Densities of solids and liquids Vp, Vs, Poisson ratio Heat production and geotherms

How to get the norms Use MELTS supp calc to go from phase chemistry in oxides to rel props of fo/fa dy/hed etc; Point count modes Make sure stuff adds up to 100

Use the Lee parametrization for garnet peridotites (STP)

Densities For solid densities, use Hacker and Abers For liquid, either IgPet (under extra params) or MELTS

Heat flow, heat production Flux (flow) - measured on the ground or in borehole Production - measured in rocks

Use Brady excel file for production Need the depth of sample - barometry etc Need K, U and Th concentrations The sum of their production equals the heat production

Heat productivity vs. heat flux relationship The crust is highly concentrated in radioactive elements such as Uranium. As Uranium decays it makes heat which is termed the heat productivity in micro- Watts per unit volume units. By measuring the surface rock heat productivity, a linear relation between heat productivity and heat flux is often found. This mean the upper crustal rocks heat production controls the heat flux. The y-intercept value is the reduced heat flow (q r ) which is from the mantle.

Temperature re-equilibration Adding sediments quickly to the top of the crust, causes a thermal disequilibrium that will be brought to thermal equilibrium over Ma time-scales. Thrusting 20 km of the upper crust over the surrounding surface quickly, creates a disequilibrium that takes greater than 50 Ma to reach thermal equilibrium.

Finally Calculate all your phys pros at T and P; Compare against seismic data; Double check possible crustal architecture arrangements using the following constraints: isostasy gravity