Untitled - Memorial University's Digital Archives Initiative - Memorial ...

124
suggests that activities of H 20 and alka lies were low enough to per mit st ability
of clinopyroxene . Amphib ole dun it e and OPXT II in l AlPP are evidence that
the acti vities o f H 20 and alka lies in HAlPPG w ere kept low by t he release of
mese components into l ALPP.
At t he present t ime, it is diff icu lt to dist inguish between rocks
precipitated enti re ly from the magma and those wl'lich have been recrystallized
and rea c ted in th e presence of mag m a. Eve n cumulate textures and chemiSlIy
o f AI-spinel and oli vine in the HA l PPG are probably the product of i.o-liU.!
recrvstallizat ion of cr-scroc: and Mg-rich olivine of LALPP parentage in the
presence of the m agma and its associated fluid .
4 .3 .2 Po ssibl e Parent Magml of t he HALPPG
11 has been pr eviously stat ed t hat t he HAL gabbros do not represent the
co mpo sit ion of the parent magma of the HAlPPG . The compositions o f HAL
gabbro s. olivine ch nopyroxenites and wenrntes do , howe ....er. reflect the
com po si t ion of the parenta l magma. They requ ire th at the magma was Iluid·
bearing, l AEE-d epleted, sr-enncnec. and was capab le of prec ipitating
plagioc lase before cli nopyro xene.
In t he upper t hrust slice in the nor thern part of the map ped area th ere are
bro wn amphibolite dykes < 1 m wide, which int rude uncor rerated w ehrlit e and
gabbro. These dykes have sharp contacts with their host and ex hibit v ariable
defo rmation. Three samples ne v e been examined; 50194, 50380 lki ndly
donated by S. D unsw ort h) and l 3 4 1. M ineralog ically t hey consist of