Cave Creek Rocks!!! EarthCache
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Welcome to Cave Creek Arizona. When I first arrived in Arizona and was driving from the airport I was shocked at the variation in land scape and composition of the rocks even within the short 45 minute drive. I started doing some research and realized how much the composition of the rock can vary from location to location. The layout above is very specific to Cave Creek. The geology varys so grealty that in some cases the percentages of different minerals can be completely different no more than several miles away.
I hope you enjoy your surroundings. Please remember to treat the area with respect and try not to disturb any of the local wildlife and plants. Enjoy!BR>
To Log this cache:
The coordinates given for this cache will place you just off the road in a riverbed. There is a mass of small-large rocks in this location. Using the information provided in the follwing pages and your GPS please answer the following questions:
1) What is the elevations above sea level at the posted coords?
2) Using the details below, try to identify which type of rock is most prominent in this location.
3) What percentage of this rock would you say is in this area?
4) What is the average size of the rocks in thi slocation? Small (pebble), Medium 2-5 inches wide, Large - 6 inches +
5) NOT MANDATORY - Post a picture of you and\or your GPS at the posted coords.
6) MANDATORY!!! - Have fun. You are Geocaching.... :-)
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Metavolcanic Rocks (Xv)
In geology, Metavolcanic rock is a type of metamorphic rock. Such a rock was first produced by a volcano, either as lava or tephra. Then, the rock was buried underneath subsequent rock and was subjected to high pressures and temperatures, causing the rock to recrystallize. Metavolcanic rock is commonly found in greenstone belts. Metavolcanic rock can contain the minerals quartz, feldspar, amphibole, pyroxene. Less common minerals can include biotite, garnet, actinolite, epidote, chalcedony, prehnite, and wodginite.
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Felsic Metavolcanic Rocks (Xvf)
Are an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series (from the Greek "oblique fracture", in reference to its two cleavage angles). This was first shown by the German mineralogist Johann Friedrich Christian Hessel (1796 - 1872) in 1826. The series ranges from albite to anorthite endmembers (with respective compositions NaAlSi3O8 to CaAl2Si2O8), where sodium and calcium atoms can substitute for each other in the mineral's crystal lattice structure. Plagioclase in hand samples is often identified by its polysynthetic twinning or 'record-groove' effect.
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Diorite to Granodiorite (Xd)
Granodiorite is a plutonic igneous rock, formed by an intrusion of silica-rich magma, which cools in batholiths or stocks below the Earth's surface. It is usually only exposed at the surface after uplift and erosion have occurred. The volcanic equivalent of granodiorite is dacite.
Diorite a grey to dark grey intermediate intrusive igneous rock composed principally of plagioclase feldspar (typically andesine), biotite, hornblende, and/or pyroxene. It may contain small amounts of quartz, microcline and olivine. Zircon, apatite, sphene, magnetite, ilmenite and sulfides occur as accessory minerals. It can also be black or bluish-grey, and frequently has a greenish cast. Varieties deficient in hornblende and other dark minerals are called leucodiorite. When olivine and more iron-rich augite are present, the rock grades into ferrodiorite, which is transitional to gabbro. The presence of significant quartz makes the rock type quartz-diorite (>5% quartz) or tonalite (>20% quartz), and if orthoclase (potassium feldspar) is present at greater than ten percent the rock type grades into monzodiorite or granodiorite. Diorite has a medium grain size texture, occasionally with porphyry.. |
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Dark Maroon Phyllite (Xp1)
Phyllite is a type of foliated metamorphic rock primarily composed of quartz, sericite mica, and chlorite; the rock represents a gradation in the degree of metamorphism between slate and mica schist. Minute crystals of graphite, sericite, or chlorite impart a silky, sometimes golden sheen to the surfaces of cleavage (or schistosity). Phyllite is formed from the continued metamorphism of slate.
The protolith (or parent rock) for a phyllite is a shale or pelite. Its constituent platy minerals are larger than those in slate but are not visible with the naked eye. Phyllites are said to have a "phyllitic texture" and are usually classified as having a low grade in the regional metamorphic facies.
Phyllite has a good fissility (a tendency to split into sheets) and will form under low grade metamorphic conditions. Phyllites are usually black to gray or light greenish gray in color. The foliation is commonly crinkled or wavy in appearance |
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