The replacement of K-feldspar by plagioclase and quartz results in a volume decrease and is favoured on high normal stress sites around the grains. We suggest that the ambient temperature, pressure and chemical activities were such that the replacement reaction was favoured, but the addition of extra strain
ABSTRACT Several examples of deformation‐induced myrmekite have been found in two amphibolite facies mylonites derived from granitic protoliths, namely a muscovite‐poor S‐C mylonite and a single foli...
and fractured, and K-feldspar replaces the plagioclase in irregular veins at top right of plagioclase and on left side. The gently-inclined, broad, black area is a fracture
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For Feldspar replacement, in 10% and 20% replacement, the decrease rates were 12.6% and 17.3% in A series, and also 6% and 8.4% in B series, respectively. The minimum R m results were observed in 30% of replacements of Mica and Feldspar which were 1.05 and 1.03 in A series and 0.98 and 0.96 in B series, respectively. It can be inferred from the
The replacement is pseudomorphic and is characterised by a sharp chemical interface which progresses through the feldspar while preserving the crystallographic orientation.
Viswanathan K, Kielhorn H M (1983) Al,Si distribution in a ternary (Ba,K,Na)-feldspar as determined by crystal structure refinement Celsian-rich American Mineralogist 68 122-124: 1983: Yugoslavia: 0: 293: 0009608: Hyalophane: De Pieri R, Quareni S, Hall K M (1977) Refinement of the structures of low and high hyalophanes Acta Crystallographica
2020-8-24 · The replacement of K-feldspar by plagioclase and quartz results in a volume decrease and is favoured on high normal stress sites around the grains. We suggest that the ambient temperature, pressure and chemical activities were such that the replacement reaction was favoured, but the addition of extra strain energy along the high-pressure sides
crystal faces of a growing K-feldspar crystal. This suggests that a facies of the original primary diorite contained zoned orthoclase. The lack of such zoning in all other K-feldspar megacrysts in other parts of the Gray's School granite lends support to the hypothesis that most of the K-feldspar has formed by replacement processes.
Diagenetic replacement of detrital albite and K-feldspar by quartz is common in Proterozoic sandstones of the Visingso Group, the Dala Sandstone Formation (southern and central Sweden, respectively) and the Brottum Formation (southern Norway). Quartz has been precipitated as a few or numerous crystals along fractures and cleavage and twinning
The degree of replacement decreases moving away from the K-feldspar cemented fractures. As the secondary albite, the replacive K-feldspars show pseudomorphism, optical continuity, lack of luminescence, widespread unconnected microporosity and compositions close to K end-member.
For Feldspar replacement, in 10% and 20% replacement, the decrease rates were 12.6% and 17.3% in A series, and also 6% and 8.4% in B series, respectively. The minimum R m results were observed in 30% of replacements of Mica and Feldspar which were 1.05 and 1.03 in A series and 0.98 and 0.96 in B series, respectively. It can be inferred from the
In early stage of K-feldspar replacement of plagioclase, the K-feldspar occurs interstitially as the K-feldspar replaces albite-twinned and zoned plagioclase along broken grain- boundary seals and
Apr 01, 2007· The replacement of plagioclase by K-feldspar has also been demonstrated to be rapid, even though it also involves a change in the Al:Si ratio of the solid phase (Orville, 1972). In a natural hydrothermal setting, when a feldspar is in contact with a fluid with which it is not in equilibrium, a replacement process is inevitable.
In early stage of K-feldspar replacement of plagioclase, the K-feldspar occurs interstitially as the K-feldspar replaces albite-twinned and zoned plagioclase along broken grain- boundary seals and. MYRMEKITE 24 OF 50. 2004-5-21 · Discussion In the Rocky Hill stock, the textural relationships and the pseudomorphism of the K-feldspar (microcline
substitute custer feldspar for kona f4 feldspar? updated wed 12 oct 11 : Jean Eiers-Page on mon 10 oct 11 Hi, Can I substitute Custer feldspar for Kona feldspar in the following recipe? Thanks for your help. Jean Ron Roy Black, ^6 ox. one of several rev. CM Oct. 2003
K-feldspars from rocks Rb in 121 2 3 4 "loNa Na in 69 K-feldspars from pegmatites ( 3 volues aboVE' 2 •J. 160 150 140 l l 130 120 110 100 90 80 70 60 50 40 30 20 10 419 Figure la. Histograms showing the distribution pat torn of Na, K, Rb, Cs, Tl, Pb, Ca, Sr and Ba in K-feldspars from rocks and pegmatites.
> Just wondering if Custer Feldspar can be used as an acceptable substitution > for G-200 Feldspar. > I'm primarily mixing glazes from Mastering Cone 6 Glazes and don't have nay > G-200 on hand. Short answer probably, they're both potash feldspars. But you may find the results a little different.
Jun 24, 2009· Oligoclase and labradorite crystals have been experimentally replaced by albite in an aqueous sodium silicate solution at 600°C and 2 kbars. The replacement is pseudomorphic and is characterised by a sharp chemical interface which progresses through the feldspar while preserving the crystallographic orientation. Reaction rims of albite, up to 50 μm thick, can be readily achieved within
in replacement processes is provided by the hydrothermal alteration of feldspar rocks in the Larvik Plutonic Complex in SE-Norway, which acts as a perfect natural laboratory. Fluid-rock interactions are visible as a colour change: the blue larvikite rock is (partly) replaced by red t˝nsbergite. It started as
Detrital feldspars most commonly undergo dissolution or alteration and replacement in subsurface settings, yet in many sandstones one also can find examples of authigenic feldspar cements. Such cements, in almost all cases, are either albite (the sodic end-member feldspar) or orthoclase (the K-spar end member)—see Chapter 2 for more details.
The replacement reactions can affect large portions (> 60%) of the primary alkali feldspar. An important distinctive feature of this type of myrmekite formation is the constant thickness of the vermicules, whereas in the K-metasomatism their thickness changes as a function of the Ca-content of the plagioclase and they also taper towards the