In the complex microprophries is very fine grained with orthoclase, perthite
, quartz, biotite, magnetite, epidote as major minerals.
Chl: chlorite film; Sty: stylolite; Pri: primary pore; Pert: perthite
; Orth: orthoclase; I/S: illite-smectite mixed-layer clays; Shri: shrinkage; AQ: authigenic quartz; Cal: calcite cement; F: Feldspar; InterD: interparticle dissolution pores; IntraD: intraparticle dissolution pores; Tuff: tuffaceous; Diss: dissolution pores; K: kaolinite; I: illite.
Plagioclase ranges from (23.8% -45.6%) Microcline often intergrown graphically and are sometimes perthitic with albite occurring as patchy perthite
. It however displays cross hatch twinning.
Microfractures in the perthite
grains contain fine-grained alkali feldspar.
The type locality for perthite
, for instance, now lies buried beneath a highway in Ontario.
Rock type An (4) Zoning (5) Leucogranite < 5 unzoned non- exsolved Fine-grained luecomonzogranite Coarse-grained zoned > patch > luecomonzogranite unzoned rod & bead perthite
Muscovite-bionte monzogranite Biotite monzogranite Biotite < 5 - 35 zoned rod granodiorite & bead perthite
Brian Thomson from Kettering said: "Tam Cowan's comments about the size of St Johnstone's crowds were out of order.
The body is occupied by petrographically uniform granite composed of perthite
, albitic plagioclase, quartz, and small quantities of biotite, opaque oxide and titanite.
1) 2) 3) 4) 5) Quartz 30 35 34 28 - alkali feldspar 60 57 63 58 - (perthite
) calcic - - - - 49 plagioclase Biotite <1 <1 - 1 1 alkali 9 8 6 11 - amphibole calcic - - - - 26 hornblende Clinopyroxene - - - - 9 Orthopyroxene - - - - 7 Olivine - - - - 3 Ore - <1 - 1 4 Accessory 1 <1 <1 1 1 minerals IUGS rock a-fG a-fG a-fGl a-fG G-N classification Abbreviations: a-fG = alkali-feldspar granite.
(3) Rischorrite is a variety of nepheline syenite in which nepheline is poikilitically enclosed in microcline perthite
The granodiorite is a relatively undeformed, medium-grained, and slightly porphyritic, and contains intensely sausseritized plagioclase in an equigranular matrix of similarly altered, finer grained plagioclase, perthite
, quartz, and equant to interstitial biotite and possibly amphibole (both now chlorite).
It is occupied by petrographically uniform granite composed of perthite
, sodic plagioclase, quartz, and small quantities ofbiotite, opaque oxide and titanite.