Sterling Hill Mine in Ogdensburg, New Jersey Photo by Dmadeo |
No, this isn't about a gold mine it's about a zinc mine
specifically the one at Sterling Hill, New Jersey that for many years produced zinc and was one
of the largest mines and the East Coast of the United
States . The ore produced from this mine is
noted worldwide for its many fluorescent minerals, but like all mines in
eventually came to it in and was closed down although it still operates as a
museum. At this mine and the ones in nearby Franklin, New Jersey form a canoe
shaped orebody hosted in marble that is been the subject of much controversy
over the years as to its origins.
During the 1960s Brian Skinner of Yale
University was working for the USGS
and with a colleague started speculating on how this ore body was emplaced.
Under normal circumstances it is assumed that the ore came from deeper down in
the bowels of the earth. However in this case under the marble was a layer of
impervious rock that apparently did not allow the ore bearing hydrothermal
fluids to rise up from below the marble.
Willemite, Franklinite and Rhodocrosite under Ultra-violet light from Sterling Hill Photo by Rob Lavinsky |
Skinner and his colleague were working in the mine one night
when the question of the deposit’s origin came up. The layer below the marble was impervious,
but the marble itself wasn’t. Many
layers of sediments were deposited above the marble including some that were
volcano-clastic in nature. These rocks
were also pervious allowing ground water to perk down from higher up that were
capable of bearing ore bearing fluids.
They came to the conclusion that the ore bearing fluids came down from above
and perked through the marble until they hit an impervious layer below the
marble. Here the ore bearing fluids
stopped and gave up their load of dissolved minerals creating the deposit.
However there is zinc minerals dispersed throughout the marble above the actual
deposits.
This is all theoretical, but there are other examples of
this same mechanism at work. One glaring
example can be found in the iron deposits found in northwestern Connecticut . For almost two centuries the iron mines in Salisbury
yielded some of the richest iron ore on earth that had its origin in the
overlaying Walloomsac formation of schist interbedded with
marble.
The same specimen as above under normal light Photo by Rob Lavinsky |
The origin of this formation is volcano-clastics that came
from an island arc that formed off the then east coast of North
America that collided with the continent during the late
Ordovician and caused the Taconic Orogeny.
This volcano-clastic material was the source of the iron that formed the
famous Salisbury iron deposits, and
supplied the magnesium that turned the limestone into dolomite. The Walloomsac formation extends south from Lake
Champlain to Manhattan
where it underlies among other things the New York Stock Exchange. Throughout its length at its base and in the
underlying marble iron deposits are sprinkled like plums in a plum pudding.
It is theoretically possible that some gold deposits that
are hosted by marble were deposited by the same mechanism i.e. leached from the
overlying deposits. A possible example
of this mechanism in action are the gold deposits of the Carlin Trend in Nevada . Another suspect is the San Pedro mine in San
Luis Potasi, Mexico . Both of these deposits are hosted in
marble. Keeping this mechanism in mind
might lead to the discovery of other deposits of valuable metals.
Bullion Exchanges is a trusted Bullion Retailer established in New York City's Diamond District.
ReplyDeleteThey have a wide inventory of items including but not limited to, precious metals that range from the gold & silver to the newly emerging platinum & palladium.
They are offering an enormous range of products appealing to first time buyers and seasoned investors.