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Black Mt. arsenic mine - One Stop Wonder

ONE STOP WONDER ANNOUNCEMENT

Our next OSW takes us to Black Mountain in Carmel Valley on June 22nd.
Date:Saturday June 22, 2019
Time:9:00 am
Location:Black Mountain Miner's Ridge Trail
Directions:-From Interstate 15, headwest on Bernardo Center Drive Bernardo Center Drive turns into Carmel Valley Road. Just past Valle Del Sur, turn left into the entrance for Black Mountain Open Space Park, Miner's Ridge Loop. - From Interstate 5, head east on Highway 56. Exit Camino Del Sur and head north. Turn right on Carmel Valley Road. Pass the first driveway and then turn right into the entrance for Black Mountain Open Space Park, Miner's Ridge Loop.

The parking lot is up the hill and is also our meeting spot! We will have a short hike on the Miner's Ridge Trail and discuss the Santiago Peak Volcanics and associated mining history.
Niland Mud Pots - One Stop Wonder

Mud Pots on the Move
OSW - Niland, Imperial County, California March 23, 2019

After months of inquiries, SDAG was granted access to a Union Pacific Railroad property where a giant mud pot forced the relocation of train tracks and continues to threaten existing tracks, a petroleum pipeline, a fiber optic cable and State Highway 111. The Union Pacific Railroad's southern California to Texas mainline parallels the eastern shore of the Salton Sea, where approximately 60 to 80 trains per day carry international goods from Asia to the interior United States.

Niland OSW - Sinkhole next to railroad tracks Dave Lynch of Caltech met us to provide safety rules and give a summary of recent mud pot activity. We then followed Dave across the railroad tracks to view a 23-foot deep sinkhole that appeared to be furiously boiling. Although geothermal activity is present in this region, the water in the pit is actually at ambient temperature, and the disturbance seen is caused by CO2 bubbling up through groundwater. The mud pot is currently being dewatered as a means to try to control it, and approximately 40,000 gallons of water are removed every day!

CO2 is present all throughout this area, resulting from the decomposition of calcium carbonate sediments spurred by geothermal activity deep below the surface. The CO2 moves up through the sediments but is only obvious in areas where groundwater is present. Where mud pots bubble up the water has been pushed up to the surface and in some cases the sediments collapse. This mud pot first appeared in 1953 and was a typical, stationary mudpot until some time around 2007 when it began to move westward. Its progress was slow at first, but since April of 2018 it has grown increasingly mobile and now has moved 240 feet from its original site.

Niland Mud Pots - One Stop Wonder No one knows exactly why these mud pots are on the move. The USGS and NASA's Jet Propulsion Laboratory are assisting with research, and Dave has some theories, but we will have to wait until they are published. Look for Dave's article in the June issue of Civil Engineering.

Niland Mud Pots - Mud-spurting volcano After the visit to the Union Pacific site, a smaller group of geologists headed out to the mud volcanoes of the Davis-Schrimpf Seep Field. A geothermal plant visible nearby confirms the presence of deep geothermal activity - a result of shallow magma intrusions associated with a spreading center at the southern end of the San Andreas Fault. Temperatures at depth can reach 300oC and higher, although by the time the CO2- laden water reaches the surface it is often at ambient temperatures or slightly warmer. The heat, however, helps to break down the sediments, releasing the CO2 gas. The result is a unique geological phenomenon of bubbling, gurgling, mud-spurting volcanoes - a delight for geologists and all!

Provided by: Jennifer Morton
Calle Guadalajara Landslide - One Stop Wonder

Calle Guadalajara Landslide - One Stop Wonder

Stephen Jacobs is leading our first OSW of 2019 to observe a large landslide in San Clemente. The OSW is scheduled for Saturday, January 5, 2019 from 10am to 12 noon.

Access to the landslide complex is via a trail leading from Calle Guadalajara. Parking near the trailhead is along the street on Calle Guadalajara between Calle Corral and Calle Reata in San Clemente. The proposed meeting time will be 10:00 am to 12:00 pm on Saturday, January 5, 2019.

An interesting landslide complex in an open area of San Clemente has progressed in size since about the mid 1990s. It represents a series of reactivated slides within an ancient landslide complex underlain by the Capistrano Formation according to the Geologic Map of the Dana Point Quadrangle mapped by Tan (1999). The latest and most prominent reactivated portion of the slide complex, which apparently formed in about 2011, is near the eastern part of the mapped area of the ancient landslide complex. This area has an approximately 15- to 20-foot high head scarp with ancient landslide material exposed in the scarp face.

Photo of landslide below...

Calle Guadalajara Landslide - One Stop Wonder



OSW - Encinitas Copper Mine - Write Up by Jennifer Morton

Encinitas Copper Mine (a.k.a. Danes Lea Mine) N33.081651 W117.208037
Rancho Santa Fe Quadrangle
Directions:
Take I-5 to La Costa Avenue, head east. Turn left onto Rancho Santa Fe Road and right onto San Elijo Hills Road. Bear right at the roadway to a closed landfill and park on the side of the road. Head south on the easternmost dirt path, next to the landfill building. Arrive at the head of Copper Creek trail. Follow this trail until you reach the waterfall and remnants of the mine workings.

OSW Encinitas Copper MineOn September 1, 2018, SDAG visited the site of the Encinitas Copper Mine in the La Costa Preserve. The old mine was situated along what is now known as Copper Creek. According to County Report 3, Geology and Mineral Resources of San Diego County, California, published by the California Division of Mines and Geology in 1963, the mine was discovered in 1887 and was worked until 1917.

We were joined by Richard Bumann, local author/historian and a descendent of one of the founding families of Olivenhain. Mr. Bumann's uncle owned the copper mine from the 1920's through 1940's, and he shared some of the history of the mine and boyhood stories of exploring the mines and at one time lowering himself into one of the shafts! Mr. Bumann confirmed that the mine consisted of two shafts, one on either side of the canyon through which Copper Creek flows. The mine was worked sporadically until 1917, producing a low-grade extract than it would be worth! Piles of light-green rocks - the remaining mine tailings - give away the locations of each of the shafts, which have since been blasted shut for safety. The shaft on the east side of the canyon consisted of two horizontal tunnels terminating at a 140-foot deep vertical shaft, and the shaft on the west side was reported to be a vertical 400-foot shaft. The shafts tend to flood with groundwater, and Mr. Bumann's uncle spent many months pumping out water and restoring the shoring in 1925, but the mine was never again worked.

OSW Encinitas Copper Mine According to the 1963 County Report, the deposit is a northwest-trending zone copper-bearing mineralization, approximately one mile long and 10 to 50 feet wide. The 1939 California Journal of Mines and Geology, Quarterly Chapter of State Mineralogist's Report XXXV describes the vein as a yellowish and black gouge between walls of dark-colored porphyry, and notes that the ore is chalcopyrite associated with pyrite.

OSW Encinitas Copper Mine Steven Jacobs provided a great overview of the formation of porphyry copper deposits. These types of deposits typically form as the result of hydrothermal activity. In the case of the Encinitas Copper Mine, as the magma body of the Western Peninsular Ranges Batholith intruded the Santiago Peak volcanics hydrothermal fluids circulated through preexisting rocks, altering these rocks and depositing metals in the matrix or as a coating in fractures on the surface of surrounding rocks.

Monte Marshall was on hand to discuss the formation of the Santiago Peak Volcanics. These are subduction-related volcanoes, similar to the Andes or the Cascades. He noted that a visible outcrop near the mine consisted of a volcaniclastic deposit - one of three types of structures typically seen associated with the Santiago Peak Volcanics. Others include flows and feeder dikes with vertical foliation.

Thank you to everyone who made this a successful OSW!