Tales of the Devil: Origin of the Rowe Schist

The earth movements that affected the Appalachian Mountains after the Taconic Orogeny   USGS

During the late Cambrian and early Ordovician a series of turbidite flows came down the continental slope of the North American craton.  This was the origin of the Roweschist formation.  Turbidites are also good sources of gold ore.  There are several examples of this kind of formation worldwide with the Witwatersrand of South Africa being the most notable.  Much of the gold ore from Timmins, ON is another example as are many of the deposits of the world.  To date the Witwatersrand has produced around 40% of the entire world’s gold supply in the past 40 years.  The gold mines found here are some of the deepest in the world that now are approaching 13,000 feet deep.

Earth movements associated with the Taconic Orogeny during the late Ordovician caused this layer of turbidite to be shoved to its present location close to the Iapetus Suture zone that locally in Connecticut and New York is called Cameron’s Line under differing names it reaches to the mountains of western Norway.  It is truly one of the largest suture zones on earth.  By definition a suture zone is also a subduction zone where rocks of oceanic origin are forced under the continental margin.  Cameron’s Line is about two miles west of the Rowe schist the formation that underlies the property belonging to the finder of the Whodunit Mine.

According to the USGS the following illustration graphically explains the Taconic Orogeny an Alpino type orogeny, a long narrow belt of mountains that formed the Taconic mountain range.  This is the orogeny that initiated the first of several mountain building events that occurred in the Northern Appalachians.  This is the orogeny that had the greatest effect on the Litchfield site.

The site itself is composed of a series of turbidite flows that flowed down the continental slope into a back arc basin behind the island arc.  This was composed of the sand and mud component illustrated in the first of the illustrations shown of the below diagram.  The Hoosac Schist on the landward side of Cameron’s line is represented by the portion marked sand.  The continental crust is represented by the Precambrian rock north and west of the site on the landward side of Cameron’s Line. 

Cameron’s Line is where the Hoosac schist and the portion marked sediment meet in a long suture line that extends from Staten Island, NY that was broken in half after the Atlantic Ocean opened during the Mesozoic and after passing through Ireland, Scotland eventually ends in the mountains of northern Norway.

When the Taconic Orogeny ended the mountains that rivaled the Himalayas in height were completely eroded away to a flat plain we know as a peneplain.  There were small mountain building events that occurred during the Silurian that although they affected the local area were so small as to be hardly noticed.  The next big event that affected the eastern seaboard occurred during the Devonian called the Acadian Orogeny.

The Acadian Orogeny produced a different type of mountain range that was much broader then the Taconic Orogeny that to geologists is a Hercyanian type orogeny that was caused when Europe sideswiped the North American Continent.  It was during this event that the Rowe schist was intruded with molten magma causing it to become a type of rock called granofels.  This action caused many secondary minerals to be deposited in the schist ilmenite being the most prominent.  The event also caused further deformation to the Rowe schist.

At the end of this orogeny the Rowe schist has stayed above sea level unlike at the end of the Taconic orogeny as the rocks were eroded smooth the ocean came back to cover the land with ocean water.

Land affected by the Acadian Orogeny.  The original path of Cameron's Line is depicted in red. 

For the most part the only Orogenies that affected the local area were the Taconic, the Silurian (?) and the Devonian.  The later Orogenies affected the lands to the south and east.

How to find hard rock gold

Gold in Quartz
Photo by Rob Lavinsky

Unlike placer gold hard rock or lode gold is much more expensive to locate, but under the right conditions isn’t impossible.  Most lode deposits are found by following placer gold deposits in a stream until the deposit suddenly chokes off then following float up hill until you finally find the Mother Lode.  Most lode deposits are always shedding float that goes downhill in an ever widening fan of the host rock.

Although gold can be found in virtually any rock type its usual home is in white, milky quartz that is readily distinguished from the host rock as termed in the mining industry “gangue.”  The white rock stands out so often pieces of it can be observed washing down mountainsides from its source with the naked eye or by using binoculars.

Although most hard rock gold is found in quartz veins that are usually readily visible, and the thinner the vein often the more gold it contains.  Another prime target for hard rock gold is the rock conglomerate where the biggest of all gold deposits are found in the Witwatersrand in South Africa.  These deposits have produced around 40% of all the gold that has ever been mined.  Deposits of this type also contain uranium and rare earth elements in payable amounts making it entirely possible to find deposits of this nature with a Geiger counter.  The gold/uranium deposits at Elliot Lake, Ontario are of this nature.

Quartz pebble conglomerate a likely place to find gold
Photo by Wiki-Schack

In many parts of the world it is extremely hard to see float because the area is covered with deep overburden so it is necessary to use other methods of finding hard rock gold; one of the most popular is using aeromagnetic maps or other geophysical methods like ground resistivity.  Aeromagnetic maps work on the principle that gold often occurs associated with the mineral magnetite or other iron bearing minerals like ilmenite causing the prospector to carefully examine the area around magnetic highs on an aeromagnetic map.

An analog multimeter that can be used for several different parameters in geophysical prospecting
Photo by KENPAI

Ground resistivity is one of many different geophysical techniques use to find ore deposits based upon the amount of underground corrosion that takes place in an orebody.  This is done using a multimeter that has high impedance and a strand of wire.  For convenience most of these rigs have 1,000 feet of wire mounted on a reel.  In use an area 1,000’ x 1,000’ is measured out on the land.  Parallel lines are drawn on its surface with readings taken from 100 feet apart to 10 feet apart along the lines.  The highest readings are connected with a line, and each successive lower reading until a map that resembles a topographic map is generated.

Any number of different parameters can be measured using this method, but the best explanation of their use is explained in a book about practical geophysics.  Parasinis authored a book on the subject that is still available today in the 1960s.