The Fluid Follow Nature’s Pathways: The “birth place” rock, with all the holes, had to be connected to the source of fluids containing what would eventually become Herkimer diamonds. These fluids come from the compression of thick sequences of mud deep in the earth, mud that would become the rock called shale, not far from the district.
Step 2a: Burial and the Nearby Marine Basin
The “birth rock” was now buried close to a deep water sea basin that was getting filled with millions of years of black mud - thousands of feet thick. It is this mud, when it got pressed into being rock, that released waves of fluids. It is the unique positioning of three earth events 1) the rock full of holes, 2) the old earthquake zone and 3) the nearby marine mud basin, which resulted in a perfect “birth place” to make Herkimer diamonds.From about 500 to 450 million years ago, large accumulations of black mud filled in a wide regions south of the Herkimer district (the Utica Shale). You can see these black rocks as you drive on interstate 90 from Albany to Syracuse. At one time these were not rock - but just a large pile of black mud. During the process of changing the pile of black mud into black shale allot of fluid was released - sort of like pressing down on a sponge full of water.
Step 2b: Continents Collide and Both Pressure and Heat Increase
Around 480 to 450 million years ago Africa smashed into North America (the Taconic orogeny). During this time heat and pressure built up in the rocks at depth near the Herkimer birth place rocks - the limestone with all the holes in it. In addition old fault zones were reactivated and new ones were formed. As the pressure and heat increased the black mud changed to rock and the rock also went through changes. These heat and pressure changes released lots of fluids. These fluids now had a natural pathway - up the fault zones and out into the limestone that was full of holes. The source of the large zones of dolomite around the faults in the Herkimer district mirrors the dolomite fault association with the nearby gas deposits. In addition, there is mounting evidence that the majority of the “black matter” seen in the Herkimer diamond cavities is left over from ancient oil….. More details about basins, fluid release. gas/oil, and mineral deposits to be added in the future.
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Updated - 03/09/2019
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photo of black shale I-90 exit
Thank you Shannon Haley Wilbur for the donation of 30 samples from the Fonda region.1/05/2019 and 3/2/2019Check out her Facebook.