With further increase in bulk Or they are homogeneously distributed in the plagioclase. At first small platelets of low sanidine a few nanometres thick and up to ∼10 nm long occur sporadically only on Albite-twin composition planes. The inner plagioclase cores are homogeneous oligoclase-andesine with Albite growth twins only, but are crypto-antiperthitic towards the outer core. The following microtextural sequence was observed. The feldspars normally have a plagioclase core and an alkali feldspar rim cores become smaller and rims larger and the An content of both decrease with distance from the contact of the intrusion. The microtextures developed during relatively slow cooling as a function of bulk composition in zoned ternary feldspars from syenodiorites and syenites in the Klokken intrusion, described in the preceding paper, were determined by TEM and their origin and evolution deduced. The official field numbers and rock definitions can be found in the description of the figures below, or see Coarse-grained ("plutonic") crystalline igneous rock or Fine-grained ("volcanic") normal crystalline igneous rock. Some of the fields are assigned to 2 or 3 rock types, which are further distinguished by their mafic mineral content or plagioclase type ( calcic or sodic). They mostly have similar field divisions, so most volcanic rocks have a corresponding plutonic rock of equivalent mineralogy (for example, rhyolite and granite). There are 2 QAPF diagrams, one for coarse grained ( plutonic) or intrusive igneous rocks, one for fine grained ( volcanic) or extrusive igneous rocks. The QAPF diagram is divided into 15 basic fields that define ranges of mineral compositions for the different classes of rocks. The corners represent cases in which only one felsic component is present, effectively 100% of either quartz, alkali-feldspar, plagioclase or foid.īecause foids and quartz are mutually exclusive in an igneous rock, the QAPF classification is always based on a maximum of 3 components, either QAP or APF, and the compositions of the rocks are plotted in either the upper or lower triangle. It is made of two ternary diagrams with the corners Q, A, P and F, A, P, adjoined to each other along their A-P edge. The composition of the rocks are plotted into a diamond-shaped coordinate system, the QAPF diagram, also known as Streckeisen diagram (named after the author of the original article). Within the QAPFM classification scheme proposed by the IUGS, rocks with less than 90 vol-% mafic minerals are classified by their content (in volume-%) of:
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