3/11/2024 0 Comments Ternary diagram of feldspars![]() ![]() The microtextures in the rims are regular cryptomesoperthitic, with (¯601) lenses or lamellae, depending on the bulk Or-content, of low sanidine in Albite-twinned low oligoclase-andesine. Thicker, through-going plates in platelet-free areas are found, which induce Albite twins in the surrounding plagioclase. 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. ![]()
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