Diabase quarries in Loudoun County to become reservoirs
There's a proposal to turn the Luck Stone diabase quarry south of Leesburg into a big reservoir for increasingly-populous Loudoun County, Virginia. It would then be followed by other tapped-out quarries in the area. Collectively storing 8 billion gallons, the reservoirs could serve the surrounding area for up to 120 days during a prolonged dry spell. The idea is to create the reservoirs by siphoning of about 40 million gallons a day from the Potomac River, starting in 2017.
These diabase intrusions are mafic igneous rocks that intruded into the crust during the opening of the Atlantic Ocean. As Pangea broke apart during the Triassic and Jurassic, a huge system of sags opened up in the crust. These low spots were the sites of (a) intense sedimentation, since water flows downhill, and (b) mafic igneous intrusions, since the thinned crust allowed decompression melting of the underlying mantle. (Partial melting of an ultramafic source usually yields a mafic distillate.)
The entire system of failed rift valleys extends along the same trend as the Appalachians, but further east, all the way up to the Bay of Fundy. Collectively, they are called the Newark Supergroup, after one of the larger rift basins in Newark, New Jersey. Dirty sandstones filling that basin were the source of all the 'brown stone' that made the brownstones of New York City. Locally, in our own Culpeper Basin, the main rock that is quarried is diabase, which has a coarser crystal size than basalt, but smaller crystals than a gabbro. It is distinguished by a lot of pyroxene.
Source for the reservoir proposal news: Today's Loudoun Extra, from the Washington Post
These diabase intrusions are mafic igneous rocks that intruded into the crust during the opening of the Atlantic Ocean. As Pangea broke apart during the Triassic and Jurassic, a huge system of sags opened up in the crust. These low spots were the sites of (a) intense sedimentation, since water flows downhill, and (b) mafic igneous intrusions, since the thinned crust allowed decompression melting of the underlying mantle. (Partial melting of an ultramafic source usually yields a mafic distillate.)
The entire system of failed rift valleys extends along the same trend as the Appalachians, but further east, all the way up to the Bay of Fundy. Collectively, they are called the Newark Supergroup, after one of the larger rift basins in Newark, New Jersey. Dirty sandstones filling that basin were the source of all the 'brown stone' that made the brownstones of New York City. Locally, in our own Culpeper Basin, the main rock that is quarried is diabase, which has a coarser crystal size than basalt, but smaller crystals than a gabbro. It is distinguished by a lot of pyroxene.
Source for the reservoir proposal news: Today's Loudoun Extra, from the Washington Post
Labels: atlantic, culpeper basin, jurassic, minerals, mining, new jersey, new york, news, triassic, virginia, water resources
2 Comments:
Is this reservoir usage wise? The fractures in the diabase could allow significant water seepage. Moreover, this diabase quarry in particular and other mines and quarries in the Leesburg - Belmont area are associated with the copper, lead and zinc sulfides, chalcopyrite, galena and sphalerite; actininolite and other asbestiform minerals; and various minerals of phosphorous, aluminum, fluorine and barium (an extraordinarily heavy nonmetal). Erosion alone generates sulfuric acid and leaches and concentrates heavy metals. Added to the various contaminants in the Potomac River water, including additional heavy metals,what might be the result?
See:
http://www.mindat.org/loc-8479.html
New Goose Creek Quarry (Luck Company Quarry), Leesburg, Loudoun Co., Virginia, USA
Ref.: Rocks & Minerals: 60: 167.
Located near Belmont Station, Loudoun Co., VA. Owned by the Luck Company. Produces aggregate in diabase traprock. Started 1972.
Mineral List:
Actinolite
Albite
'Ancylite'
Apatite-(CaF)
Apophyllite-(KF)
Augite
Babingtonite
Calcite
Chalcopyrite
'Chlorite Group'
Datolite
Diopside
Epidote
Galena
Goosecreekite (TL)
'Hornblende'
Kainosite-(Y)
Laumontite
Loudounite (TL)
Malachite
Mordenite
Natrolite
Prehnite
Quartz
Sphalerite
'Stilbite'
Thomsonite-Ca
Titanite
See Also:
http://www.upei.ca/~physics/p261/projects/acidprec1/Heavy%20Metal%20Leaching.htm
http://sweetwatervisions.com/Pages/sulfidemine.html
This quarry was flooded from Goose Creek during Hurricane Agnes (1972). 20 years later, it was still full and had to be pumped in order to resume mining. Regardless, any contamination resulting from infiltration is similar to the background conditions as the quarry is not in direct contact with the local aquifer (which isn't really widely used as a drinking water source anyway). Eventually, the water will be made potable using state of the art technology at a facility that hasn't yet been constructed and the EPA will ensure it meets requirements for drinking water.
This plan is ingenious for several reasons. Water will be withdrawn only during high flows and at a slow rate in order to minimize any impact to the riparian and aquatic habitat. The entire region benefits, as a large reservoir is constructed in a suburban area without the associated land acquisition/flooding, dam construction and environmental impacts. Also, a mined quarry is a huge liability and eyesore to the community...this plan gives it a non-intrusive and useful second life.
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