ERTH 3207 Lecture Notes - Lecture 1: Metamorphic Rock, Subduction, Radiogenic Nuclide
9 Dec 2016
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Document Summary
Metamorphism takes place between 250-700 degrees due to propeties changes texture mineralogy composition (metasomatism) below 250= diagnosis for weathering. Process of metamorphic reaction: rocks break and begin to > Conditions: p,t,x (composition) time is needed for the process to occur, if not enough time the process will not take place. P,t,x occurs slowly, but once it reaches its peak metamorphic conditions there is no change fluid added can reset everything sensitive to temperature changes vs. pressure. Chemistry diffusion : diffuse elements with small amount of fluid along grain boundaries. Nucleation: form core of new mineral crystal growth. Temperature heat source frim 1. radiogenic heat production ex. Parallel to surfa(cid:272)e, it"s a sta(cid:271)le ther(cid:373)al steady state stru(cid:272)ture i(cid:374) o(cid:272)ea(cid:374)i(cid:272) (cid:272)rust o(cid:272)(cid:272)urs. Steady state geotherm: temperature increases with depth geothermal gradient: 25 c/km in a steady state stable thermal rated crust. Heat flow where there is a change in temperature gradient; needed for metamorphism to change texture, mineralogy and composition.
