Road side Earthcache. Turn-off unto Solomonsdale at Diep river
bridge this cache is on the paved section, road became gravel. Save
to park away from the N1.
To understand this EarthCache it's importent to undertake some
educational tasks that relates to the Earth science at the
site.
First we have to understand how this deposit of magnetite
quartzite fit into the Big picture. There is some good-looking
magnetite quartzite in the cutting, which is dense and will pull a
magnet.
To do this cache take a magnet with it will be so mutch more
fun. But you can do this without a magnet if you know
magnetite.
The Renosterkoppies deposit is in the Pietersburg greenstone
belt that is part of the Bushveld Igneous Complex.
Pietersburg Greenstone belt
diagram
In the Northern Kaapvaal Craton (Renosterkoppies Greenstone Belt,
Pietersburg area) tectonism took place under amphibolite facies
conditions at ca. 2.75 Ga (2.75 billion years) and can therefore
not be related to any events in the Limpopo belt. Thus the
different tectonic units have different late Archean
tectonometamorphic histories. The Bushveld Igneous Complex (or BIC)
is a large layered igneous intrusion within the Earth's crust which
has been tilted and eroded and now outcrops around what appears to
be the edge of a great geological basin. Located in South Africa,
the BIC contains some of the richest ore deposits on Earth. The
reserves of platinum group metals (PGMs), platinum, palladium,
osmium, iridium, rhodium, and ruthenium are the world's largest,
and there are vast quantities of iron, tin, chromium, titanium and
vanadium. Gabbro or norite is also quarried from parts of the
Complex and rendered into dimension stone. The site was discovered
around 1897 by Gustaaf Molengraaff.
Bushveld Igneous Complex
diagram
Magnetite Lustrous black, magnetic mineral,
Fe3O4.
It occurs in crystals of the cubic system, in masses, and as a
loose sand. It is one of the important ores of iron (magnetic iron
ore) and is a common constituent of igneous and metamorphic rocks.
It is found in the Pietersburg greenstone belt. Magnetite ore has
lower iron content and must be upgraded to make it suitable for
steelmaking. Magnetite ore is suitable for processing into iron ore
pellets for use in modern steel production and currently accounts
for approximately 50% of global iron ore production. The magnetic
properties of magnetite enable it to be readily refined into an
iron ore concentrate. While magnetite is generally a lower-grade
deposit, it is globally accepted as a viable and high-quality
feedstock for the production of premium quality, low impurity
steel. The processing route for magnetite requires crushing,
screening, grinding, magnetic separation, filtering and drying. The
final product is a high iron grade magnetite concentrate (+65% Fe),
with typically very low impurities.
Metamorphic rocks (Magnetite and Quartz at
site)
Metamorphic rocks are the most complex rock class, forming as
they do by the compression and chemical alteration of other rocks,
both sedimentary and igneous. Metamorphic rock is the result of the
transformation of an existing rock type, the protolith, in a
process called metamorphism, which means "change in form". The
protolith is subjected to heat and pressure (temperatures greater
than 150 to 200 °C and pressures of 1500 bars[1]) causing profound
physical and/or chemical change. The protolith may be sedimentary
rock, igneous rock or another older metamorphic rock. Metamorphic
rocks make up a large part of the Earth's crust and are classified
by texture and by chemical and mineral assemblage (metamorphic
faces). They may be formed simply by being deep beneath the Earth's
surface, subjected to high temperatures and the great pressure of
the rock layers above it. They can form from tectonic processes
such as continental collisions, which cause horizontal pressure,
friction and distortion. They are also formed when rock is heated
up by the intrusion of hot molten rock called magma from the
Earth's interior. The study of metamorphic rocks (now exposed at
the Earth's surface following erosion and uplift) provides us with
very valuable information about the temperatures and pressures that
occur at great depths within the Earth's crust. Some examples of
metamorphic rocks are gneiss, slate, marble, schist, and
quartzite.
Must involve visitors undertaking some educational task that
relates to the Earth science at the site. This could involve
measuring or estimating the size of some feature or aspect of the
site, collecting and recording data (such as time of a tidal bore),
or sending an e-mail to the cache owner with the answer to Earth
science related questions they obtained by reading an information
display. While photographs may be requested, they do not take the
place of other logging requirements. Taking a photograph alone or
asking people to do internet research does NOT meet these logging
guidelines. Requests for specific content in the photograph (must
include the visitor's face, for example) will be considered an
additional logging requirement and must be optional. Cache owners
may not delete the cache seeker's log based solely on optional
tasks.
To Log your earthcache find, please do the
following (answers by email please, not in your log): You can go
ahead and log your find then email the answers to me within 7 days,
if not your log will be deleted.
Click on hennieventer top of the page and
Send Message
Questions:
1.Take your magnet and find a piece of magnitite. How does the
grain look like?
2.How does the magnitite feel comparing the other rocks around
it?
3. Find a piece of magnetite quartzite. Looking at the rock
explain briefly how the magnetite separate from the metamorphic
rocks like quartz?
4.Looking at the magnetite at coordinates, the lines is in
layers of fine sedimentation. To your understanding doing this
earthcache how did this layers of sediment became a rock?
5. Take a photo with your GPS at Coordinants. Place photo with
your log.
I have used sources available to me by visiting the site, the
Polokwane library, internet, research, and asking questions to get
information for this earth cache.
Acknowledgements:
Geological Journeys (A Travelers Guide to South Africa’s
rocks and land forms) Nick Norman and Gavin Whitfield.
Wikipedia
I am not a geologist. Since Earth caching is educational I also
leant a lot through the research. Hope you will enjoy this
Earthcache
