If I were to find silicon inclusions with assorted lesser components
in granitoid rocks here, how might that be explained?
Dear Peter, the body of your message has a different subject to the
header, are you asking about SiO2 inclusions in diamond or are you
asking about granitic rocks? Free quartz makes up about 30% of
granites, you dont find silicon as a native element anywhere. If you
are trying to associate diamonds with granitic rocks, give up
because the oxygen fugacity is all wrong, not to mention the
temperature and pressure. What assorted lesser components are you
thinking about/finding? more precise is required before
an offer of a decent explanation.
I have never heard of quartz inclusions in diamonds. The rocks
diamonds form in do not have free quartz and if that was available
in a melt, the carbon would “burn” and leave you with carbonatite
rock. The chemistry of certain common minerals are used as indicators
of diamond deposits and they give a fairly precise geothermometry and
some level of geobarometry as well s the forementioned oxygen
fugacity. Same applies to platinum deposits and to a degree, most
economic metal deposits.
Nick Royall
If I were to find silicon inclusions with assorted lesser components in granitoid rocks here, how might that be explained?
Well, I don’t know about SiO2 in diamonds, but silica (quartz) is
not just an inclusion in granite. It’s one of the minerals that
defines granite… If you’ve got granite, than by definition, you have
silica.
Now, if you’ve got silicon (the metal), then that would be rather
unusual…
Bottom line, your message doesn’t seem to match your message subject
header. Just what were you asking? Silica or Silicon? in Diamonds, or
in Granitic rocks?
Oh, and what’s Granitoid? Another variant of “granitic”?
(the other Peter)
Peter-
Elemental “silicon” will not be found as an inclusion in granitoid
rocks. Silicon dioxide (silica) might be, since true granites
typically consist of quartz, potassium feldspar, and mica, plus minor
accessory minerals. More basic granitoids will also contain dark
minerals in addition to the usual trio of quartz, feldspar, and mica.
Since diamonds are most frequently associated with ultrabasic rocks,
which means that free silica is rare or absent, a direct association
of diamond and silica is very unlikely, if not impossible. I would
leave it to a petrologist who has made a study of diamond in
kimberlite or lamproite to comment further on the possibility of a
close association of diamond and silica. Please note that kimberlite
and lamproite are actually consolidated ejected material rather than
granitoids, which are assumed to have crystallized in deep-seated
plutons.
I hope this helps you to find an answer to your question.
Dick Davies
I was reading “Diamond Synthesis and Carbon Solubility in a Hydrous
Granitoid System” from adsabs.harvard.edu
The authors are talking about the 4,000 km. long felsic (as in
feldspar-quartz) formation through Russia and China with its
diamonds containing inclusions of quartz plus traces of other
elements. This led the researchers to examine two possibilities as
causing the inclusions in interaction with the dissolving of carbon
and growth of diamonds and they tested the possibilities in the lab:
(1) a Si-in-magma; (2) Si-in-water.
I am wondering if it has applicability to some quartz diorite
formations I am prospecting here in BC though I don’t know if you
would call that felsic or acidic.
Do you or Nick at Baroque beads think those “two systems” (magma and
aqueous) might help to explain the 10% range in specific gravity of
diamond (including bort and carbonado) with their great range in
colour and transparency?
As Nick noted diamonds are not as “invincible” as the Greek word
denotes. They can burn. Can they also have various chemicals mixed
with them as C allotropes are transformed over millions and billions
of years? Could the physical chemistry of C over such a time span
also include quantum effects in the final diamond makeup since we are
now told that diamond, not silicon wafers may be a key to building
the “chip” of the quantum computer?
Here are some pieces of relevant infomation to further the
discussion. I would recommend some googling and examining of
pictures online as well as text.
(1) The Audubon Field Guide gives an SG range of 3.1 to 3.5 for the
various forms of C allotrope diamond in the field which is > 10%.
(2) Yes, I agree with you and Nick about the role of pockets,
cracks/faults and chemicals mixed in with C which may alter colour
and SG greatly especially given that some diamonds are found in rock
thought to have formed 3 bya and there is enormous TIME for these
changes to happen to the original C. So we ask about the history of
C over billions of years.
(3) In addition to googling add the Harvard material there is a
series of Princeton reports with quotes like “The role of water in
the growth of carbonado awaits further explanation” and “in contrast
to kimberlite diamonds, the geochemical signature of carbonados are
systematically crustal”. I think the word “GROWTH” is important in
contrast to the flash formation of diamonds in meteorites etc.
including the Discovery TV demo of backyard explosions to produce
diamonds (which everyone should rush out to try in yard or basement
or apartment balcony of course).
(4) Dispersion of the fluids which were discussed and demonstrated
empirically in the Harvard material may be impacted by quantum
effects as we read in Physics Today of August 11/10 “Quantum Effects
Turn Pore Diffusion on its Head” and in particular Zero Point Energy
may cause molecules to disperse to different degrees and “by a
substantial margin” with H2 and D2 used in the experiments.