Title

Petrologic and geochemical study of crustal xenoliths from Calbuco Volcano, Chile (latitude 41°20ʹS)

Document Type

Thesis

Degree

Master of Science (MS)

Department

Geosciences

First Advisor's Name

Rosemary Hickey

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Gautam Sen

Third Advisor's Name

Grenville Draper

Keywords

Igneous rocks, Chile, Calbuco Volcano, Inclusions

Date of Defense

8-8-1990

Abstract

Twenty Four samples of xenoliths and country rocks from the 1961 lava flow of Calbuco volcano have been studied. Fourteen samples have been analyzed for major elements and P, Ni, Ba, Cr, V, Zr, Sc, Y, and Sr. Five of these samples were further analyzed for Sm, Nd, Sr, and Pb isotope ratios. Seventeen samples were studied under the microscope and three samples were analyzed by microprobe for their pyroxene compositions.

Based on petrographic studies xenoliths were divided into three groups. Fine grained xenoliths (groups I and II) probably formed from metamorphosed MORB-like basalts, whereas coarse grained xenoliths (group III) were apparently derived from cumulate minerals that crystallized from the Calbuco magma. The fine grained xenoliths were probably entrained in magma at intermediate levels of the crust, near the stability limit of amphibole to form pyroxene and plagioclase. In the coarse grained xenoliths amphibole that formed at depth dehydrated as the xenoliths were brought to the surface. The country rocks are apparently unrelated to the xenoliths.

Identifier

FI13101505

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