In bowens reaction series how do the tetrahedra in feldspar differ from those of silicates?

Answer 1

The simple answer is... Feldspar has a much higher complex and stable tetrahedral orientation in comparison to that of any other Silicate variation higher up on the reation series latter.

Feldspar is one of the most stable variations in orientation of, what boils down to, silicate tetrahedra. Because Feldspar is technically a form of silicate tetrahedra orientation, I am assuming you are asking how the silicate tetrahedra orientations vary from its most simple (i.e. Olivine) to its mosts complex (i.e. quartz/FELDSPAR) forms. Esentially a Silicate Ion SiO4^-4 is the most basic building block of FELDSPAR.

Knowing this, as you move from the top of Bowen's reaction series, we see a gradual stabilization of the various Silicate tetrahedral orientations. These orientations include (in order of stability/complexity):

[TOP OF REACTION SERIES]

Individual (Singular form) Silicate Tetrahedra (i.e. Olivine)

Chain (Linear form) Silicate Tetrahedra (i.e. Pyroxine)

Double Chain (Bilinear form) Silicate Tetrahedra (i.e. amphibole)

Sheet Silicate Tetrahedra ('2-D' form) (i.e. Mica: Biotite or Muscovite)

Framework Silicate Tetrahedra ('3-D' form) (i.e. FELDSPAR)

[BOTTOM OF REACTION SERIES]