A case of secondary overgrowth on primary fieldspar of porphyry . A new combination of twinning laws in fourlings. Twins according to the first axis and perpendicular to it
Abstract
In one of the thin sections of quartz porphyry from the Vtoro-Blagodatny mine, I came across an interesting case of fractures within feldspar grains being filled with feldspathic substance of the same composition and in the same orientation. The rock is quite strongly altered: the feldspars are abundantly strewn with muscovite dust. The thin section field is cut by several veins, apparently filled with new growths. In this case, depending on whether the vein cuts through the groundmass or the feldspar segregations, it is filled either with an aggregate of feldspars and quartz or with feldspars alone, with such a slight difference in orientation compared to the mineral of the grain cut through by the vein that it cannot be quantified. Feldspar veins are characterized by significantly greater transparency due to the absence of muscovite inclusions.
None