From Albuquerque Journal, October 03, 1988
Bore Hole Offers Peek at History, Potential of Core
By Byron Spice, Journal Science Writer
Christmas comes several times a day along the rim of the valley Caldera in the Jemez Mountains.
For geologists involved in boring a hole deep into the ancient, collapsed volcano, it comes in the form of rock cores, decoratively wrapped in metal pipe and delivered from a hard-hat Santa’s 75-foot-tall drill rig just up the hill.
The cores have been arriving in the scientists’ plastic-sheeted lean-to since late July, first in 10-foot lengths and now in 20-feet lengths. Each 2-inch-diameter cylinder of rock reveals more of the volcanic system’s secrets, which the mountains have been hoarding for hundreds of thousands of years.
The project is part of the Continental Scientific Drilling Program and is designed to increase understanding of volcanoes, geothermal energy systems and the way in which mineral deposits are formed. Researchers expect to complete the drilling in the next few weeks, by which time the bore hole may reach a depth of 7,000 feet.
“Holy smokes, look at the pyrite in there,” cried Jeff Hulen, a geologist with the University of Utah Research Institute, as the latest gift of rock core was dumped into a plastic trough one day last week. “Isn’t that beautiful stuff? Look at this vein,” he said, pointing to a long golden streak of pyrite spiralling around the core.
Only minutes earlier, the rock had been hoisted from a depth of almost 4,800 feet, where temperatures are greater than 500 degrees Fahrenheit. The core was still warm to the touch as Hulen and Jamie Gardner, a geologist at Los Alamos National Laboratory, scanned it to find any obvious prizes.
Within minutes, the scientists focused on the bottom of the core, which they found was composed of “intrusive” rock – once molten rock that never reached the surface when the volcano erupted. Its presence surprised and pleased the researchers – “We’ve got an intrusive!” – because the drill long ago had passed through all the volcanic rock near the surface and was deep within sedimentary rock.
This intrusive rock suggested that a previously undiscovered finger of rock might extend from the chamber of molten rock, or magma, that lies three or four miles beneath the caldera. The magma chamber already may have solidified into granite, but its heat continues to feed the area’s many hot springs.
“This is detective work at its finest,” said Gardner, who is co-principle investigator with Hulen of the drilling project.
The bore hole is along the western rim of the Valles Caldera, near a tiny settlement known as Sulfur Springs. It is the third and deepest hole drilled in the giant depression as part of the Continental Scientific Drilling Program, which is sponsored by the Department of Energy, U.S. Geological Survey and the National Science Foundation.
It will cost $1.2 million just to drill the hole, known officially as VC-2B. About scientists from around the world are involved. Total expenditures could reach $4 million to $5 million during the course of the five-year project, Gardner said.
Geologists increasingly are turning to drilling projects such as this to provide new dimensions to their science. Rather than relying on the two-dimensional clues of surface features to predict underground structure, geologists can use rock cores and bore holes to obtain the third dimension of depth and the fourth dimension of time. By the time VC-2B bottoms out, researchers will have gotten a glimpse at rock dating back 1.6 billion years.
The 14-mile-wide caldera itself dates back 1.1 million years, when a huge volcano erupted so rapidly that it left a void beneath it, resulting in its collapse. The most recent eruption in the caldera system was 130,000 years ago.
It’s one of the three youngest caldera systems in the country and is well preserved. “What we learn here will have applications to other geothermal areas around the world,” Gardner said.
Under the supervision of Sandia National Laboratories, the drilling rig is using diamond-studded bits to cut a continuous core of rock. The continuous core is important because it not only shows scientists what rock types exist and at what levels, but preserves the rock’s structure as well, Gardner said.
The drilling rig is the largest diamond-core rig in the country and was imported from Australia fro the project, said Peter Lysne, head Sandia’s geoscience drilling office. Sandia has high hopes for using the advanced drilling technology for exploratory oil and gas executives at the drilling site last Friday.
The caldera is the source of the Bandelier tuff that covers much of the Jemez Mountains to a depth of 1,000 feet. But the volcanic system extends much deeper than that, with hot, pressurized geothermal fluids – mainly water – seeping through tiny cracks in the underlying sedimentary rocks.
Steel liners are being installed as the hole is drilled. Next year, researchers will perforate the lining at various intervals to sample the fluids, which may contain chlorine, arsenic, boron, silica or other dissolved material, depending on depth and rock type.
Energy companies are interested in tapping these geothermal fluids, letting them flash to steam to power electrical generators. Some of what is learned in the current project may aid in geothermal power development.
However, those hot fluids also dissolve minerals and concentrate them in ore deposits. Those deposits have proven to be of interest in older calderas that have cooled to the point where mining is practical. Scientists hope the drilling project will allow them to observe how these ore bodies are deposited.
For instance, rock cores from a depth of 1,152 feet revealed for instance, ruby silver, a sub-ore-grade mineral often found near bodies of silver ore, Hulen said. That might be evidence of an ore body in the process of forming, or the ruby silver may have migrated in the geothermal fluids from a lower ore body.
Likewise, deeper cores have been composed of a jasperoid rock, which suggests the presence of gold deposits, Gardner said.
The drilling is scheduled to end once the bore hole penetrates several hundred feet of Precambrian rock. Previous geothermal drilling has shown this layer of rock to be composed of granite or granitic gneiss through which little fluid circulates.
From Los Alamos Mini Review, January 01, 1982
Fenton Hill during drilling of well EE-3. This 20-acre site in the Jemez Mountains of northern New Mexico contains both the pioneering Hot Dry Rock Research (Phase I) System and the follow on Engineering (Phase II) System. The Research System, behind the red drilling rig, has operated successfully for more than a year at heat- extraction rates up to 5 million watts with no detectable environmental effect. The Engineering System, under construction, will investigate the economic feasibility of generating electricity for commercial use.