The most abundant mafic mineral
is subhedral to anhedral olive green to green brown magnesio-hornblende (10% to 30%), which is often accompanied by anhedral olive green to green brown biotite (8% to 10%).
As an exception, the Marjamaa pluton is more differentiated with the anomalously high magnetic central part containing hybrid granodiorite with hastingsitic hornblende as the main mafic mineral
. The major and trace element contents of the Estonian porphyritic potassium granites are close to or overlapping those of typical Finnish rapakivi and comparable with the less differentiated granitic phases from the Wiborg and Laitila plutons (Kuuspalu 1975; Kirs et al.
The mafic rocks can be divided into two broader types one of which contains hornblende and the other clinopyroxene as characteristic primary mafic mineral
. They are commonly fine-grained and aphyric to porphyritic.
The quartz content is higher than in the gabbroic rocks and the main mafic mineral
is hornblende rather than clinopyroxene.
The characteristic mafic mineral
in granites is annitic to siderophyllitic biotite.
Three rock types fall under the broad category of "biotite-rich granitoids", which refers to granitoid rocks with relatively high (10-30 modal %) mafic mineral
content (predominately biotite) in the SMB.
Pressure, a parameter with a generally minor impact on the stability of mafic mineral
phases at upper crustal conditions, was fixed at a constant value of 0.1 GPa.
The leucodiorite is generally white to light grey, medium- to coarse-grained and inequigranular, and typically consist of a framework of subhedral plagioclase grains and interstitial mafic minerals
(chlorite and amphibole), locally forming up to 30% of the rock (Fig.
(1) Melteigite is a dark colored plutonic rock that is part of the ijolite series and contains nepheline and 60-90% mafic minerals
, especially green pyroxene.
To simplify the 40 plus elements analyzed for the ET3 sequence, the tephras have been broken down into three basic components: glass, plagioclase and mafic minerals
. A simple mixing program is used to calculate a weight percent for each phase in the tephras using elemental concentrations for the whole rock and for the individual mineral phases or glass.
typically comprise ~10% of the granite.
have been replaced with diopside, sphene and hedenbergite in the endoskarn.