Peggy's Veins EarthCache

Peggy’s Veins

Geological History

The geological history of the Peggys Cove area began over 470 million years ago with the deposition of mud and sand in a deep ocean near ancient Africa.  As the thickness of sediment increased, the mud and sand sere compacted into rocks named shale and sandstone. Movement of the ocean basin toward ancient North America resulted in a major collision of crustal plates.  Theis collision initiated a period of mountain building 400 million years ago. The shale and sandstone were crumpled and folded, and the added heat and pressure transformed them into metamorphic rocks known as slate and quartzite.

Heat generated from the collision melted rocks and the base of the earth’s crust 370 million years ago. The molten material intruded upward until it cooled and solidified into granite. Uplift, weathering and erosion removed several kilometers of overlying rock, finally exposing the granite that is visible in Peggy’s Cove.

Veins

Veins are mineral deposits which form when a preexisting fracture or fissure within a host rock is filled with new mineral material. Quartz is often found in veins that cut through rocks.  The crack might form during folding of the rock in mountain-building processes, by shattering during tectonic events, by a decrease in pressure during the uplift of a rock, or because a rock cools down and shrinks. Although the term "vein" suggests this, the veins of quartz and other minerals are usually not thin tubes, but rather thin sheets. The veins can form under various conditions, and depending on these conditions, may or may not bear quartz crystals in them.  Not every white lines are quartz, sometimes it may be Calcite(secondary filling in wear and crack zones). The veins can form under various conditions, and depending on these conditions, may or may not bear quartz crystals in them.

The simplest type of a quartz vein is the filling of an already present crack in rocks. The crack might form during folding of the rock in mountain-building processes, by shattering during tectonic events, by a decrease in pressure during the uplift of a rock, or because a rock cools down and shrinks. Hot brines that percolate the rocks and originate at greater depths with higher temperatures will precipitate the minerals they carry with them in cracks at lower temperatures and pressures. This process may continue until the crack is completely filled or may stop before, leaving "pockets" in the vein that are sometimes outlined by crystals. Hot brines that enter a crack in the rock from some distant hot source like a granite pluton first cool and precipitate most of their load rather quickly. The result is milky quartz, either massive or made of interlocked milky quartz crystals. Later, when the crystal growth slows down, the crystals may get less milky or even clear. In the majority quartz veins, most of the quartz is precipitated as massive, milky quartz, and well-formed crystals, if found at all, are only a small portion of the vein filling.

To log this Earthcache visit the viewing location.  Please answer the following questions and send in a timely manner to my geocaching profile or email. Answers not received will result in deleted logs.

Question:

1 - How long is the line of quartz at ground zero?

2 - How wide is the vein of quartz?

3 - What is elevation at this point?

4 - Is the vein below or above tide line?

5. [REQUIRED] In accordance with the updated guidelines from Geocaching Headquarters published in June 2019, photos are now an acceptable logging requirement and WILL BE REQUIRED TO LOG THIS CACHE. Please provide a photo of yourself or a personal item here to prove you visited the site.