Upsection

[caption id="attachment_572" align="aligncenter" width="610"] Feldspar porphyroclasts in the ultramylonite of the Pofadder Shear Zone[/caption] Porphyoclasts are deformed crystals found in a metamorphic rock. In a mylonite weaker minerals deform though crystalplastic processes and form a "toothpaste" texture. Stronger minerals will try to resist the deformation, but may break and stretch along with the weaker minerals. As the weak minerals recrystallize, they will flow around the remnant stronger minerals. [caption id="attachment_573" align="aligncenter" width="610"] Feldspathic porphyclast in the ultramylonite of the Pofadder Shear Zone[/caption] Do you have a cool rock to share? Submit it to FridayRocks[at]Upsection[dot]com

[caption id="attachment_564" align="aligncenter" width="610"] Conjugate Deformation Bands[/caption] Deformation bands are mm wide shear offsets that typically occur in  porous rock such as sandstone at shallow depths (Aydin 1978). Offsets on deformation bands are typically small and may be distributed across the entire length of the structure (cm to kms). Brittle deformation via breaking and crushing of grains creates deformation bands which are filled with a gouge or cataclasite. Deformation bands have important implications for reservoir permeability and will typically host a cement. Fractures that are at angles less than 90 degrees to each other are called Conjugate fractures. The orientation of fractures and offsets may be used to determine the stress state in the rocks during deformation (Anderson 1942, Jaeger and Cook 1969, Olsson et al. 2004). Assuming the above photo is a 2-D example, how do you think Sigma_1 and Sigma_3 are oriented? Anderson, E....

"In every outthrust headland, in every curving beach, in every grain of sand there is the story of the earth" - Rachel Carson

[caption id="attachment_541" align="aligncenter" width="610"] Asbestos in Serpentinite and Blueschist[/caption] The rock in this photo as three components. Serpentinite (Green-yellow in photo), blueschist (blue-grey in photo), and asbestos (white-green fibrous vein in photo). Blueschist forms through the metamorphism of basalt at high pressure and low temperature. Serpentinite is a metamorphic rock formed in a low pressure environment through a reaction between ultramafic rock from the Earth's mantle and water. The reaction is called "serpentiniztion" The asbestos mineral is often associated with serpentinite. I found this rock when scrambling at the bottom of a cliff on the Big Sur coast of California. There were many small faults which sheared and mixed the different rocks types.

[caption id="attachment_548" align="aligncenter" width="610"] All done![/caption] Wide Angle lenses make it easy to capture big scenes. Not everyone has a wide lens, so there is a nice work around for capturing those large scenes. It takes a combination of taking multiple photos across the scene and some post-production software to combine the photos together. NOTE: This method of creating panoramas is not unique or original. There are many methods and software out there for creating panoramas. This is just my process. Step 1: Take the photographs This is arguably the most important step because if this gets botched then the whole panorama scene won't work. The key here is to overlap the pictures. I typically start at the left side of the scene I want to photograph. Take the photo then pan your field of view slightly right. Roughly 30% overlap with the previous photo seems to work well. [caption id="attachment_551" align="aligncenter...