The Fascinating Process of Gold Formation in Quartz Veins
Summary
TLDRIn this script, Bruce explores the geological processes that led to gold deposits in quartz, focusing on Western Australia's Eastern gold fields. He explains how, around 2.5 billion years ago, tectonic activity and magma chambers caused gold to rise through faults. Bruce discusses the importance of looking for iron-rich rocks, quartz veining, and signs of multiple mineralization phases to find gold. He also advises prospectors to search for laminated or brecciated quartz and to be aware of the value of large structures and GPS locations for potential gold finds.
Takeaways
- 📚 Gold mineralization in Western Australia is believed to have occurred around 2.5 billion years ago, shortly after the Earth's formation.
- 📚 Gold is often found in quartz because quartz, being less dense, rises first in geological processes.
- 📝 The geological process involves faults in the Earth's crust that allow magma and mineral-rich fluids to rise towards the surface.
- 📝 Gold is typically deposited in iron-rich rocks like greenstone belts, gabbros, dolerites, and banded iron formations due to its reaction with iron.
- 📝 Prospectors should look for quartz veining that has experienced multiple phases of breaking and reforming, indicating repeated mineralization.
- 📝 Brecciated quartz, where quartz appears broken and re-cemented with mineral-rich fluids, is a promising sign for gold deposits.
- 📝 Laminated quartz with thin black lines represents multiple phases of mineralization, which could indicate gold presence.
- 📝 The presence of iron staining in quartz, showing red, brown, or black colors, suggests gold may have precipitated out of the mineral-rich fluids.
- 📝 Erosion over millions of years has brought gold deposits to the surface, making them accessible for modern prospectors.
- 📝 Prospectors should look for large structures, iron-rich rocks, and stained quartz to increase their chances of finding gold deposits.
Q & A
What is the significance of the time period 2.5 billion years ago in relation to gold mineralization?
-2.5 billion years ago is a major phase of gold mineralization, particularly in Western Australia's Eastern gold fields. This period is significant as it was not long after the formation of the Earth, and the geological processes during this time contributed to pushing gold up through the crust.
What geological structures are believed to have played a role in bringing gold up from deep within the Earth?
-Faults and magma chambers were the key geological structures that facilitated the movement of gold. As the Earth's crust broke due to tectonic activity, magma chambers provided a source of molten rock that, when differentiated, allowed lighter minerals like quartz to rise first, followed by heavier minerals such as gold.
Why is quartz often associated with gold deposits?
-Quartz has a lower specific gravity (around 2.6 to 2.65), making it one of the first minerals to rise through the fault zones created by tectonic activity. As it moves upwards, it can carry gold with it, leading to the association between quartz and gold deposits.
What is the role of iron-rich rocks in the formation of gold deposits?
-Gold-bearing solutions tend to react with iron-rich rocks, leading to the precipitation of gold. This is why greenstone belts, which are iron-rich, are often areas where gold is found. Banded iron formations (BIFs) are also significant as they provide alternating layers of iron-rich sediments and silica that can attract gold.
What does the term 'differentiation' refer to in the context of magma chambers?
-Differentiation in magma chambers refers to the process where lighter minerals and elements float to the top, medium ones remain in the middle, and heavier ones sink to the bottom, creating layers. This分层 process is crucial for the separation and eventual rise of gold.
Why are quartz veins with multiple phases of mineralization more likely to contain gold?
-Quartz veins that have experienced multiple phases of mineralization indicate repeated fracturing and reforming, which increases the likelihood of gold being deposited during these events. Each phase can introduce more gold into the vein.
What are the characteristics of 'breciated quartz' and why is it significant for gold prospectors?
-Breciated quartz is quartz that has been broken and re-cemented together, often with different colors indicating multiple mineralization events. It is significant for gold prospectors because the fracturing and movement of the quartz can lead to the concentration of gold within these structures.
How does erosion play a role in exposing gold deposits at the surface?
-Over millions of years, erosion has worn down mountain ranges and removed layers of sediment, bringing gold deposits closer to the surface. This process has made it possible for present-day prospectors to find gold that was once deeply buried.
What advice does Bruce give for finding gold-rich quartz?
-Bruce advises looking for structures with big, deep quartz veins, especially those in iron-rich rocks. He also suggests examining quartz for signs of multiple mineralization phases, such as laminated or brecciated quartz, and looking for staining that could indicate the presence of gold.
Why are GPS coordinates important when finding potential gold deposits?
-GPS coordinates are crucial for marking the locations of potential gold deposits. They allow prospectors to return to these sites for further exploration and claim the area as a potential mining site.
Outlines
🌋 Geological Processes and Gold Mineralization
This paragraph discusses the geological processes that led to gold mineralization, particularly in Western Australia around 2.5 billion years ago. It explains how faults in the Earth's crust allowed magma chambers, similar to those under present-day volcanoes, to push gold upwards. The process of differentiation within these magma chambers caused lighter minerals like quartz to rise first, followed by heavier minerals such as gold. The paragraph also touches on the importance of finding structures with repeated phases of breaking and reforming, which are more likely to contain gold deposits.
💠 Quartz and Gold in Fault Zones
The second paragraph delves into the specifics of how quartz and gold are associated in fault zones. It describes the process of mineralization where lighter elements like quartz are the first to be pushed up through faults due to pressure from magma chambers. The paragraph emphasizes the importance of looking for quartz veining that has experienced multiple phases of breaking and reforming, which indicates a higher likelihood of gold presence. It also highlights the significance of iron-rich rocks in the area, as gold-bearing solutions will react with these to precipitate gold. The types of quartz veins to look for are those with laminated bands or brecciated quartz, which show signs of multiple mineralization phases and破碎的 quartz pieces re-cemented with more quartz, indicating promising areas for gold deposits.
🏔 Erosion and Surface Exposure of Gold
The final paragraph explains how the gold and quartz that were once deep within the Earth's crust have been exposed on the surface due to millions of years of erosion. It discusses how the land level has lowered as a result of this erosion, causing the once-subterranean gold deposits to become accessible. The speaker advises prospectors to look for specific signs in the field, such as brecciated or laminated quartz, and to search for structures that indicate deep chambers where gold may have precipitated out. The importance of noting GPS locations and keeping findings confidential is also stressed, as these could potentially be valuable gold deposits.
Mindmap
Keywords
💡Quartz
💡Gold mineralization
💡Faults
💡Differentiation
💡Magma chambers
💡Greenstone belt
💡Banded iron formations (BIFs)
💡Quartz veining
💡Breccia
💡Erosion
💡Prospector
Highlights
Quartz is often found with gold due to geological processes that push gold up through the Earth's crust.
Major gold mineralization occurred in Western Australia around 2.5 billion years ago.
Gold mineralization happened shortly after the Earth's formation about 4.5 billion years ago.
Faults in the Earth's crust allowed gold to rise from deep magma chambers.
Magma chambers are similar to those found under present-day volcanoes.
Differentiation in magma chambers causes lighter minerals like quartz to rise.
Quartz has a specific gravity around 2.65, making it one of the first minerals to rise in fault zones.
Gold, being heavier, rises later in the faulting process.
Iron-rich rocks like greenstone belts are areas where gold is likely to precipitate out of mineral-rich fluids.
Banded iron formations are also areas where gold can be found due to their iron content.
Quartz veins that have experienced multiple phases of breaking and reforming are promising for gold.
Laminated quartz with thin black lines indicates multiple mineralization phases.
Brecciated quartz, where the mineralization has broken the quartz, is a good sign for gold deposits.
Iron staining around quartz fragments is a sign of gold mineralization.
Over millions of years, erosion has brought gold deposits to the surface.
Prospectors look for structures, iron-rich rocks, and stained quartz veins.
Visible gold can sometimes be found in high-grade structures like quartz reefs.
GPS locations of potential gold sites and keep them secret for future exploration.
Transcripts
hey it's Bruce here for the part-time
prospector
have you ever wondered how quartz is
tied up with with gold and gold tied up
at the courts and why doesn't it occur
in Sandstone or something else or some
other type of rock
so
it all comes down to how did the gold
get up to where basically we're finding
at the moment so this is a bit of the
story
of my understanding
of the geological processes that push
gold up through the crust so
we're gonna go back in time about two
and a half billion years
and so that is a time that most
geologists believe there's a major phase
of gold mineralization occurring within
Western Australia occurred in different
times in different other places around
Australia and around the world but in wa
for the Eastern gold fields that runs
from Norsemen and the South to walloona
in the north and maybe a little bit
further
that is the main sort of driver is the
gold occurred around about 2.5 billion
that is with a B so it's a long long
time ago when you think of the Earth was
supposedly made about 4.5 billion years
ago this is events that occurred not
that long after the formation of the
Earth and so the Earth was quite a
different place from what it is today
there might have been some microbes
hiding some corners but there was
nothing really there was no dinosaurs
anything like that so this is a very
very horrible place
so what was driving the gold to come up
so as these structures The Faults that
were forming there was a lot of false
breaking across the continent they were
bringing up the good stuff from Below so
if we do it on the Whiteboard here just
do a very simplistic cross section
through the Earth so this is the surface
of the Earth
now none of this is to scale okay I'm
just doing this for demonstration
purposes and we've got trees growing on
the top now
just to show you that that's where the
atmosphere is and remember back in those
days there was no trees
again
down in towards the center of the Earth
it doesn't even have to be at the center
of the Earth but
at least 50 to 100 kilometers below the
surface of the
the Earth that exists at 2.5 billion
years ago there was these magma changes
magma Chambers these are similar to The
magma chambers that exist underneath
present-day volcanoes and so these are
hot bubbling
just oozing masses of molten rock just
just
waiting to explode they're into
phenomenal temperatures down there
they're talking hundreds if not
thousands of these integrated and a
phenomenal pressures yeah thousands of
of pounds per square inch if you want to
use the old thing I don't know what the
exact number is you could look it up but
it's very very high pressures very high
temperatures
and so this stuff is look just looking
for a way to get out and as soon as a
break occurs in the ground be it from
tectonic activity be it from a meteorite
impact be it from whatever the ground
breaks
and this has caused the fault that runs
along the ground now this fault doesn't
have to be a massive width it doesn't
have to be like the ones you see on the
movies where they open up and all houses
falling in it can just be half a
millimeter wide a millimeter wide maybe
a centimeter wide that's just enough
to release the pressure that's in one of
these Chambers
but one of the ancient
of these Chambers at the moment
is as it's bubbling away
starting a process called
differentiation
and that is what's happening is when you
get
lighter minerals and elements are
starting to float to the top medium ones
in the middle and heavier ones at the
bottom
and so it's a bit like you know oil and
water oil floats above there is lighter
it floats above the water and so you get
these layers occurring around the
outside now nothing to scale here
so you've got a lot of stuff at the top
heavier stuff at the bottom
and it's just sitting there waiting to
go
a fault comes along
for whatever reason hopefully you can
see this blue
and it it occurs and it does not have to
reach the surface vast majority of the
time it never reached the surface and
this could have stopped
tens or more kilometers below the
surface so 10 plus kilometers below the
surface is this point here
because when this high pressure
liquids and gases down there is that
sorry it's liquids inside there's no gas
down there high pressure liquids finds
this zone of low pressure
is that it starts to immediately race up
the crack
so it starts bubbling its way up and
pushing it and as it pushes this way up
this zone of weakness this fault Zone
it's applying phenomenal pressure and a
nominal effect on the surrounding rocks
and it's pushing these rocks apart
pushing them and the more it pushes the
part the more that it sucks up stuff
from down the bottom
so the first stuff that's going to zoom
up this full plane is going to be the
light stuff
and what is the light stuff you guessed
it quartz quartz is an SG or specific
gravity around about 2.6 2.65 and it's
one of the first things to zoom up the
pipe so as it zooms up it's going up up
the system here pushing apart pushing
and pushing and pushing apart and
actually reacting with the the
surrounding rocks
if there's a subsequent phase of
mineralization or faulting
okay now this is the key one part here
if this subsequent phases the next
heavier stuff starts to go up the pipe
and there's another event more heavier
stuff things and the last stuff to go up
the pipe I'm calling it pipe but I mean
go up the fault zone is there heavier
stuff the heaviest minerals going up and
what is the heaviest minerals the
heaviest mineral that you and I are
interested in Gold that's when it goes
up so what we want to find is a
structure
let's head repeated and multiple
breaking and reforming and more
um quartz and minerals been ejected in
and over and over and over and over
again and the more times this happens
the more likely is we're going to get to
the stage where the heavy stuff was
brought in
but this rock is not uniform in in
composition there might be some you know
best Ultra one bit granites and another
bit and so on like this but if you've
got a band for example
of iron-rich rocks
dollar rights and something like that
even basalts okay they are iron rich
the the courts the the the fluids coming
up bearing goals gold will start to
react with the iron rich rocks
this is why we fight we tell everyone
when you're going out looking for gold
look at the greenstone belt because the
greenstone belt is iron rich rocks it is
the the the the the gabbros the dollar
rights the uh the basalts
and also look in the banded iron
formations
okay so the banded ions are alternating
layers of iron-rich sediments with
silica and chert and back and forth it
keeps alternating and so if this is a
zone of banded iron or Biff
sometimes you show it on a um on the um
geological map as a Sif s i f stands for
sedimentary iron formations basically
the same stuff
the the goal-bearing solutions will be
racing up the fault intersecting this
iron rich thing and start to precipitate
out of of um of the solution and so what
and what you end up having is
concentrations of gold in here
and minor concentrations of gold along
here
so
what we're looking for when we get out
there
is we want to find iron rich girl iron
rich rocks
we want to find quartz veining
and we want to find quartz veining
that's experienced multiple phases of
breaking and reforming and researmenting
and breaking again and more minerals
coming in so so what does that rock look
like we all know what the the classic
white quartz blow looks like looks white
like the snow almost it's hungry quartz
basically as as we used to call it
hungry courts has nothing in it it's
basically that first lot of stuff that
came up and nothing followed up
what we won't look for is quartz that if
I draw a zoomed in layer of a quartz
vein here this is quartz country rock on
their sides and so the next layer of of
injection of mineralized bearing fluids
will either come up along the edges
and we'll start seeing laminated bands
sitting near the edges of the courts so
you may be a a baron inner core my
bearing has an almost solid white and
they're and they're hanging wall
football areas will be laminated and
they can be very close together we're
talking maybe millimeters apart to maybe
centimeters apart usually no more than a
few centimeters apart and they thin
black lines in the courts each one of
those thin black lines represents a
phase of mineralization coming in and
the more of these black lines you got
he wrote the more phases of
mineralization there was but that that
one form of mineralization occurs and
that generally occurs down towards the
southern end of the gold Fields down in
Norseman for example there's a mine down
there and fortunately closed in the
1990s
but they pull them more than a million
ounces out of this quartz Reef I was
about between one and two meters wide
and it ran more than an ounce per ton
and that ran like that for Neti oh I
don't know started in the 30s and wound
up in the 90s so what's that 50 to 60 is
so there was a lot of gold in that
system they're just sitting in these
laminations
the other type of mineralization to keep
an eye open for and this is a somewhat
more common one is that as the
mineralization comes up it starts to
break this quartz
and so you get the sort of change colors
here you get this sort of pattern all
over the thing I've just broken quartz
you must probably seen it around it's
called brechiated quartz
and so the mineralization is coming up
and as it comes up it moves from around
each one of these rocks and these little
it almost looks like
um looks like
concrete with not much cement in it just
a lot of rocks that have been slightly
moved apart and re-cemented together
with more quartz or generally what we're
looking for is a lot of iron around
these these quartz bits this quartz
fragments and so the more iron that's in
the system and the same thing up here
the more iron they got pumped up the
more likely that gold is going to
precipitate out so that more busted up
you can see the quartz and the more iron
staining so that's the Reds the Browns
sometimes into the blacks
that is the good mineralization that's
coming up so if you bust a bit of rock
quartz open and inside and the fresh
broken faces you can see all these sort
of broken up pieces resemented together
with all sorts of different colors in it
this is looking really promising
now as the time went past
you know as I said this is may have
stopped 10 10 kilometers below the
surface so you may be wondering well how
did that how did that quartz get on the
surface now that we can metal detect it
well simple little process called
millions and millions and millions of
years of erosion Australia is one of the
most geologically stable countries in
the entire planet and not much has
changed for millions of years and so
what has happened is that huge mountain
ranges have just been eroded away and
dumped into the sea and so what is
happening is now the land level is down
here somewhere tens of kilometers of
sediment has been washed off the
continent and dumped into the sea you
can only guess how much gold has gone
dumped into the seam
and so now this stuff is now poking up
through the surface and this is what us
as present-day Prospectors and as past
Prospectors have been trying to find so
keep your eye open for this magic
breachier quartz
or look for the laminated quartz and
keep an eye open so what you're looking
for the all together is we want
structures big structures the longer the
structure it is the more deeper it goes
It goes all the way down to these
Chambers short look quotes especially if
you're looking at geological maps don't
go deep
okay so you'll want big structures you
want Iron rich rocks you want quartz
veining and when you get out there pick
up the quartz and have a look if it's
nice and white to the color of this
white board maybe time to move on to the
next next bit but look for the quartz
that is stained colors
break it open is the color inside the
rock or just on the outside which is
maybe present day weathering is put it
on
so look for those the things then if
you've got broken up quartz laminated
quartz look inside that you may be lucky
enough to even see a visible gold
and so um it can get the very high
grades in these sort of structures say
ounce baton sometimes multi-anses
patanum there's a lot of voids in there
for the gold to precipitate out so keep
an eye open for that
if you find that in the field
you know GPS that location because you
want to come back to it over and over
and over again grinut
Miller checked as much as you can and
keep it under your hat because this
could be a bonanza shoot
hopefully that helps you
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