Tuesday, May 31, 2016

The Approach to Titus Canyon: Amargosa Narrows, Bullfrog Pit, and the Original Bullfrog Mine

We're officially on the Titus Canyon leg of our larger Death Valley trip—a round trip odyssey that will take us to and near a number of places. This section of our journey began with the last post, which was centered around Beatty. I’ll be complementing my February photographs with photos from a similar journey MOH and I took back in the late spring of 2009. So, let's get on with it! We'll begin by leaving Beatty.

There are two ways to get to the Titus Canyon road from Beatty. I usually forget that fact because it's generally been years between journeys into the canyon. Consequently, I seem to end up on this route one time, and that route the next time, alternating routes without really thinking about it. Then I wonder why the road, the signs, and the overall lay of the land don't look the same as the last time I passed through the area.
Beatty's main intersection: a 4-way stop.
We went one way in 2009, turning left at Beatty’s main intersection, which kept us on U.S. 95 as we drove east and then south through and out of town. We passed the dirt turnoff to Fluorspar Canyon (might there be some fluorite up there?) and passed into the Amargosa Narrows. Not far beyond the Narrows, we turned right onto the unsigned paved road to the Beatty Airport, which goes by an obscure ghost town, Gold Center. Airport Road turns to dirt beyond the airport.
The Amargosa Narrows: Precambrian Z rocks crop out on the right, left, and straight ahead.
We went the other way this past February, going straight on Nevada S.R. 374, the Daylight Pass road, at the same intersection. This paved road winds through a bit of the Bullfrog Hills, going by Velvet Peak and Paradise Mountain. It then meets up with Airport Road near the Bullfrog pit of the currently inactive Bullfrog open pit gold mine.
The Bullfrog pit, as seen from the dirt portion of Airport Road, looking across a sea of blooming creosote (from the early May trip, 2009).
The Bullfrog gold mine—AKA the Barrick Bullfrog gold mine—was in operation from 1988 or '89 through 1998, when it produced about 2.4 million ounces of gold from two main open pits, the Bullfrog pit and the Montgomery-Shoshone pit, and from at least one related underground project, the North Extension. Discovery of these ore deposits began in 1982 with St. Joe Minerals Corporation (overall history is described in some detail here, here, and here). The exploration property then passed through several companies in quick succession through a series of acquisitions or buyouts, going from St. Joe to Bond Gold Corporation, then to Lac Minerals Ltd (or LAC Minerals Ltd, depending on the year—this company went back and forth with its name several times in a few years), and then to Barrick Gold Corporation.

The deposit is hosted in Tertiary volcanic rocks, mostly ash-flow tuffs that are cited by Castor et al (1989) as being correlative with the Miocene Timber Mountain Tuff, which has age dates ranging from about 10 to about 15 Ma (Geolex). In fact, the host formation was mapped by Maldonado et al (1990) as the Rainier Mesa Member of the Timber Mountain Tuff.

I had a tour of the Bullfrog pit back in the late 1980s or in 1990, while I was working for Former Mining Company. Bond Gold was probably the operator when I was there, and the mine was just called the Bullfrog mine. We learned then that much of the overall low-grade ore is concentrated in veins, breccias, and stockworks, and we thought at the time the deposit would be fairly difficult to make money at. It later surprised me that a large company like Barrick got involved in the mining. (I have no idea how the economics really played out; so much can depend on the up front expenditures a company has made and the price of gold during production.)

The deposit formed near the end of an extreme extensional event that took place in the area between 11.4 and 7.6 Ma (Castor and Weiss, 1992Weiss et al, 1995; Castor et al, 1999). Although ore is partly hosted in and controlled by structures in the upper plate of the Bullfrog Hills detachment fault, it's not generally considered to be a detachment-related type of ore deposit (although knowledge of detachment faulting and related structural models would be indespensible for making discoveries in the Bullfrog mining district).

A little farther down the Daylight Pass Road, about six miles from the center of Beatty, the Titus Canyon dirt road heads WSW toward the Grapevine Mountains.
Turnoff to the Titus Canyon road.
The Titus Canyon road is a dirt road of variable character, narrow and washboardy in many parts, and entirely one way east to west. It isn't possible to turn around once you get going, and from asphalt to about "Tan Mountain," [name from Panoramio photo no longer available] there are few pullouts. It's possible that one could exit the road in two or more places within this first section, but it's not clear to me that any of these possible exits are really roads.
High clearance 4x4 vehicles are recommended!
Although 4WD is not usually necessary along most sections of the road, high clearance is a must, and 4WD can become necessary at any time (especially during bad weather). I think the road is blocked from the east when bad T-storms or flash flooding are expected, but I'd always want to check the weather to avoid getting stranded during a bad washout, like the kind the Death Valley area experienced in October, 2015.

This is what the October flooding looked like, during and after:

Don't get caught up in one of these!

Somewhere between the Titus Canyon warning sign and the Death Valley sign, you can look off to the north and see some classic Nevada ash-flow tuff formations, in this case tilted moderately along two detachment faults. The visible roads and workings are in the area of the Original Bullfrog mine, a little less than four miles west, as the crow flies, from the Bullfrog open pit.
Tilted volcanic rocks on Bullfrog Mountain (the highest point in the photo), with the Original Bullfrog mine not far left of center.
Wildflowers and creosote are in bloom in this May, 2009 photo. More precise photo and location information can be had by perusing the map near the end of this post.

I got to fooling around, saving this Google Earth image of Bullfrog Mountain from a similar angle as my photo above.
Google Earth image of Bullfrog Mountain.
Then I fiddled a little more and shortly had a geologic map overlay of Bullfrog Mountain. The two USGS maps used here are the Geologic map of the northeast quarter of the Bullfrog 15-minute quadrangle (Maldonado et al, 1990) and the Geologic map of the northwest quarter of the Bullfrog 15-minute quadrangle (Maldonado, 1990).
The same Google Earth image with two kmz file overlays.
What fun! Okay, this was so much fun, I went ahead and made the image match my photo more precisely, and then added a few geologic labels.
The photo, again, for comparison with the image below.
Geologic overlay of Google Earth (G.E.) image, labeled.
This is a good part of the Bullfrog Hills in which to see the results of the extreme extension that occurred in the area during the Miocene, although I'm not sure if its possible to actually place a finger on the main (or secondary) detachment surface. For the most part, the detachment faults are shown on the maps as dashed beneath Quaternary cover. In only three areas is either detachment fault mapped in the hills where we might be able to go look at the fault planes, and in only two places are dip measurement shown, and both sites are in the low hills to the east of the photo and images.

As for the rest of the local geology, the mylonitized lower plate Precambrian rocks are easily reconnoitered in the light colored hill on the far left of my photo (lower left of the G.E. geologic image), and the tilted volcanic section is easily walked in the hills above the Original Bullfrog mine. The main volcanic formations, oldest to youngest (west to east, left to right), are as follows: Ts3, mostly sandstone, shale, and conglomerate; Tql, quartz latite lava flows; Tlr, the Lithic Ridge Tuff; Tbt2, bedded tuff; Tcb, the Bullfrog Member of the Crater Flat Tuff; Tbt3, bedded tuff; Tpc, the Tiva Canyon Member of the Paintbrush Tuff; Tbt4, bedded tuff; and Tmr, the Rainier Mesa Member of the Timber Mountain Tuff. The Op on these maps is the Ordovician Pogonip Group, here consisting of limestone only 60m thick. The Zm consists of Late Proterozoic metamorphic rocks that have mid- to late Miocene cooling ages related to the regional extension.

Bullfrog ore.
The lower trenches at the Original Bullfrog mine used to be a great place to stop when driving through the area. (The location dot in the last image shows the site of the original mine, not the lower trenches; the lower trenches are more easily seen in the last photo as the small color anomaly below the location of that dot.) The easily unearthed quartz-amethyst veins contain v.g. and other neat minerals (see this post and next week's post). Much of the mineralized material was mined out in the 1980s (or earlier?), and a bunch of it was placed on a nearby heap leach pad. I doubt that leaching was an efficient way of recovering gold and silver from this ore, and we used to bemoan the placing of all this great specimen material out to leach. Not long after my first introduction to the area, which was probably in about 1986 or a little later, someone—no, I really can't won't say who—came and scraped the leach pad, removing all the rock in order to recover and melt the gold and electrum down for a wedding ring (at least that's the story I've heard). I visited the area most recently on the last day of the last millennium (depending on when we say the millenium started). I camped on one of the drill roads after wandering around the roads, trenches, and prospects. I didn't find much. If you ever happen to stop by the area, remember that you're probably on patented (private) ground, at least up near the original mine site, although I don't remember seeing any signs.
The Death Valley National Park boundary on the Titus Canyon is marked by signs, a fence, and a cattle guard.
Here's where we'll stop our journey today, right at the eastern boundary of Death Valley National Park (as an oldtimer, I keep wanting to call it a National Monument).

Location map

Related Posts (in order of posting):
Death Valley, "Super" Blooms, Turtlebacks, and Detachments
Death Valley Trip, Part 2: More of the Badwater Turtleback Fault
Death Valley Trip, Part 3: Northward, and over Daylight Pass
Death Valley Trip, Getting There: Wave Clouds beyond the Sierra
Death Valley Trip, Getting There: A Hike to Pleistocene Shorelines

Death Valley Trip, Getting There: Walker Lake, Road Stories, A Bit about Copper, and Some Folds near Luning

Death Valley Trip, Getting There: A Jeep Trail, Folds and Cartoons of Folds, Even More Folds, and Boundary Peak

Death Valley Trip, Getting There: Highway 95, Redlich, Columbus Salt Marsh, and Another View of Boundary Peak

Death Valley Trip, Getting There: Coaldale, Black Rock, Lone Mountain, and the Boss Mine

Death Valley Trip, Getting There: Black Rock to Lida Junction to Beatty

Beatty: Old Buildings, A Fold, and Onward toward Titus Canyon

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