University:
Massachusetts Institute of Technology
Course:
12.520 | Geodynamics
Academic year:

2023
Views:

344

Pages:

1
Author:

corineuphuistic

Feldspars, Amphiboles, and Sheet Silicates The point of this lab is to refresh your memory of the appearance of the common rock forming feldspar and pyriboles in thin section. Thin Sections: Il-007 – This section contains a great example of coarse perthite. Identify distinguishing characteristics of the two felspars and sketch a perthite grain. NE 82 (2 sections)- These sections contain Riebeckite and a single (now exsolved) feldspar. Notice the strong pleochroism in the riebeckite. Is the feldspar a perthite or antiperthite? SC 34 – Plagioclase – Find several grains and determine the An content. What is the rock type? SC 1 or I1- 016 – This section contains quartz as well as well as 2 coexisting feldspars. Identify the distinguishing characteristics of the 2 feldspars. Il-023 – This section contains myrmeckite. Find an example and sketch it. SC 43 – Find two examples of Granophyric texture and sketch them. 84-3a and 84-6 These are thin sections of lavas from the San Juan volcanic field. 84-3a is a post-caldera rhyolite dome and 84-6 is Fish Canyon tuff. Phenocrysts include quartz, plagioclase and sanidine. Distinguis among these 3. develop a set of diagnostic characteristics for distinguishing among these three phases.