Kibblehouse Quarry, Perkiomenville, Marlborough Township, Montgomery County, Pennsylvania, USAi

Regional Level Types
Kibblehouse Quarry	Quarry
Perkiomenville	- not defined -
Marlborough Township	Township
Montgomery County	County
Pennsylvania	State
USA	Country

A stone quarry originally owned by Mr. R.K. Kibblehouse.

The Kibblehouse Quarry is excavated in hornfels, thermally metamorphosed mudrocks, on the western flank of the Sassamansville anticline. The stratigraphic section exposed in the quarry is just above the Perkasie member, a prominent black lacustrian unit in the middle Passaic formation, and just below the Sassamansville diabase sill. The rocks were originally predominantly red sediments but are now very dark maroon to nearly black. A subordinate number of beds were less iron-rich and, in some cases, more calcareous. These lithologies are now shades of brownish or greenish gray.

Because little of the sediment exposed in the quarry was very calcareous and because it was beneath the diabase it was not as severely altered as some hornfels in the Newark Basin. There are no “spotted slates”. Most of the changes are more subtle and include recrystallization of the hematite pigment to specularite or, much less commonly, magnetite. Recrystallization of the clay minerals is also a major change. However, most of the secondary minerals postdate the recrystallization of the rock to hornfels and result from subsequent hydrothermal circulation.

Intrusion of diabase imposed a steep thermal gradient in the nearby sediments. This gradient drove convective circulation of connate formation brines. Because of the low permeability of the Passaic formation mudstones and hornfels fluid circulation was focused into the available network of fractures. At Kibblehouse Quarry the mineral assemblages in fracture filling veins reflect a wide range of temperature.

Although Kibblehouse Quarry has long been Pennsylvania’s best known locality for zeolite minerals it also became known, in the 1970’s, for cobaltite and other related sulphides. These minerals were restricted to a single bed that was greenish gray and quite flinty and occurred as sharply euhedral crystals both in veins and replacing the hornfels. Cobaltite has been found elsewhere in the region. Cobaltite, in pyrite, was widespread at the Cornwall and Grace iron mines. Because of the association of cobalt and the diabase some writers have proposed the diabase as the likely source of the cobalt. However, much of the secondary mineral deposition in the Newark Basin involved connate formation brines and distinctly postdates the period of volcanism and intrusion that occurred at the very beginning of the Jurassic, circa 201 Ma.

Redbed type copper deposits are common in the Newark Basin. The metal concentrating processes that leach copper from the sediment and produce redbed copper ores can also concentrate and transport other metals including cobalt and nickel (Rose and Bianchi-Mosquera, 1993). For several reasons the sediments are a much more likely source of metals than the diabase. It is likely that the principal role of the diabase was to provide the heat to drive fluid circulation.

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