Serpentine Post Updated

I just updated my Serpentine: A Group of Minerals post from last summer with some new geoblogosphere links relating to fibrous and asbestiform minerals, including erionite, a zeolite group of minerals that can occur in acicular to fibrous mineral habits. The reason for the update is that the Mineralogical Society of America recently released their Proposed Position Statement on Asbestos, as reported on more thoroughly by Chuck Magee at Lounge of the Lab Lemming and Steven Schimmrich at Hudson Valley Geologist (links below).

• Erionite and Cancer in Cappadocia, Turkey (Olelog, November 5, 2010)


• Guest Post - Naturally Harmful Metals and Minerals (The Geology P.A.G.E., December 29, 2010)


• Concerns over erionite dust as cancer source (Arizona Geology, January 5, 2011)


• Mineralogical Society of America proposes a position statement on Asbestos (Lounge of the Lab Lemming, March 1, 2011)


• Asbestos (Hudson Valley Geologist, March 9, 2011)

I'm particularly amazed that any regulatory agency would use a length:width ratio of 3:1 to describe a mineral as fibrous. Plagioclase would therefore be fibrous much of the time (though certainly not asbestiform), as would these huge cave crystals of selenite.

Geology off the Road: a bit of Tuff, Fossil Leaves, and EarthScope

It was a gray, early December day, but we continued our exploration on backroads near Middlegate Station. From the the exposures of flow-banded and brecciated rhyolite near Highway 50 — this was before The Shoe Tree had been cut down and could be used as an excellent landmark — we headed north on the main dirt road into the valley between the two southern branches of the Clan Alpine Mountains, the valley of Bench Creek. We took a sharp right at the first opportunity, within about a half mile of the pavement (the turn can be seen in the next-to-last picture of the previous post in this series).
The side road took us up the main wash, where we were tasked with looking for "little white flakes" of the middle Miocene Middlegate Formation, a formation composed of coarse- to fine-grained, often tuffaceous, sometimes zeolitized lacustrine sediments with interbeds of tuff, all lying unconformably on the older volcanic rocks of the Clan Alpine and Desatoya Mountains. A short distance up the wash road, we came to this exposure of white rocks... and though the weathering pattern looked blocky rather than flaky to me, we stopped to check it out.

Darn, we'd pulled over for a poorly welded lithic-rich ash-flow tuff, no doubt older than the rocks we were looking for. We moved on quickly, continuing up the wash.
Following the main wash road as we had been instructed by a hand-drawn map given to us at Middlegate Station, we finally came to a saddle overlooking this sedimentary section. These are the same tuffaceous sediments that can be seen north of Highway 50 when driving between Cold Springs and Middlegate gap, where the Shoe Tree used to live. The sediments were deposited in a small Miocene basin known as Middlegate Basin. Leaf fossils and petrified wood are reported in these rocks, and the zeolite erionite has been mined, at least in a small way, near the junction of S.R. 722 (old Highway 50, former Route 2) and Highway 50.
We trekked over to the white patches we could see from the saddle, and wandered around the overly muddy area looking for leaf fossils, breaking open numerous small slabs of white tuffaceous shale. We were unsuccessful for some time, and that's because we were in the wrong place. Close, but not quite.

Part of the Eastgate 1:24,000 topo map via MSRMaps courtesy USGS; X marks the saddle, not the fossil locations; sections are a mile on each side.

The saddle roads form a crude X in the center of this Google Earth image.

In order to find the fossils, you should not stop at the saddle (we had turned left and had parked on the narrow muddy ridge northwest of the saddle) but should instead keep driving down a fairly steep over-the-saddle road to the ENE; then, near the bottom of the hill, you should turn and drive southeast down another wash to a main wash heading SSE to south. In fact, while wandering around before driving over to the one fossil site we found, we could see a small hill with small diggings. That hill, located near the bottom of the GE image, is where we found the fossils.
It looked like the area had been pretty well picked over — we banged around quite a bit and only took these meager specimens. I suspect there are better localities, possibly shown here. I haven't the vaguest idea which of the many possible Middlegate flora leaf types (or stems, seeds) are represented by our bits and pieces. See these three lists (from Table 1 in Axlerod, 1985).

This plant growing near the saddle caught our eye as an unusual bush, then after our eyes became attuned to it, we saw it everywhere.

After fossil hunting, we tried to exit southward out of the wash. It was ultimately too muddy, and I don't think it's easy to find an Eastgate Wash crossing without a good map or current air photo. So we drove back to the saddle, up the steep road, and back down to the main wash road.
After trying for some unknown reason to drive south toward The Shoe Tree, and then stopping just barely in time before entering an impassable field of mud, we drove back to the main wash road and saw a fence on a little hill. We drove up to it and found this EarthScope installation.
This particular EarthScope observatory, is one of several plate boundary observatories strung across central Nevada near Highway 50.
This is Station P068's GPS receiver, with Fairview Peak in the background.
As we leave the wash, near our first tuff stop, Fairview Peak looms in the distance.

Some References:
Axlerod, D.I., 1956, Mio-Pliocene floras from west-central Nevada: University of California Press, 54 pp.

Axlerod, D.I., 1957, Late Tertiary floras and the Sierra Nevada uplift: Geological Society of America Bulletin, vol. 68, p. 19-46 [abstract].

Axlerod, D.I., 1985, Miocene floras from the Middlegate Basin, west-central Nevada: University of California Press, 279 pp.

Barrows, K.J., 1980, Zeolitization of Miocene volcaniclastic rocks, southern Desatoya Mountains, Nevada: Geological Society of America Bulletin, v. 91, no. 4, p. 199-210 [abstract].

Burke, D.B., and McKee, E.H., 1979, Mid-Cenozoic volcano-tectonic troughs in central Nevada: Geological Society of America Bulletin, v. 90; no. 2, p. 181-184 [abstract].

Eakin, T.E., 1962, Ground-water appraisal of Gabbs Valley, Mineral and Nye Counties, Nevada: Nevada Department of Conservation and Natural Resources, in Ground-water Resources - Reconnaissance Series Report 9, 54 pp.

Papke, K.G., 1972, Erionite and other associated zeolites in Nevada: Nevada Bureau of Mines and Geology, Bulletin 79, 36 pp [link to purchase].

Inside the Interzone

On the fourth day of my journey to the GSA meeting, I made my way to Portland from Eugene via some non-interstate roads that took me through Corvalis, home of The Interzone, Lockwood's favorite coffee shop.
I went inside and met that coffee shop denizen, the geological, political, satirical blogger at Outside the Interzone.

It's a colorful place, bustling with activity. Students and others come and go, and people hang around writing, studying, blogging, and what have you.

Bicycles are everywhere outside, which is a good thing, because if you don't happen to have a university parking sticker, you are unlikely to find a nearby parking space that lasts longer than an hour (or was it two?). I didn't want to feed the meter, because the meter maid was out in full force, looking for people with California plates anyone overstaying their welcome. I parked in three different parking places, the last one being several blocks away.

But don't let that stop you from dropping in: the coffee is good, the company is excellent!
Lockwood was a great host. He immediately bought me an Americano with room for cream, then we both sat at his table with our respective laptops plugged in and open, looked at routes to Portland on Google Maps, chatted, got over-coffeed (I did, anyway), read some blogs, and chatted. As I was leaving, Lockwood gave me a specimen of natrolite in calcite, which I was duly instructed to give to Callan Bentley of NOVA Geoblog when I got to the geoblogger meetup in Portland Monday night (photo here). Mission accomplished!
Yes, I really was there, on the inside, looking outside at the Interzone sign.

Mining and Exploration News

Just a few summaries and links to mining and exploration stories out recently. Excuse some dorky titles. How can you tell which titles are dorky? Easy, the dorky ones are mine.


From Ron Schott's Geology Picks:
Not so Good Oil and Gas Exploration in Washington state

From Geology.com:
Surprise, surprise, there's a new gold rush in CA!
Internet Addiction - do YOU suffer from it? (Oops - not mining related unless you are reading this blog post over and over again!)

Also from Geology.com:
Geologists are needed in Australia

But in other reports (and comments), jobs aren't really available unless you KNOW SOMEONE.

Canada can't attract women into mining jobs according to this article - also from Geology News - although on my spring field trip, all the women geologists were Canadian, except for me.

Mining and petroleum-related jobs are still going strong - from Arizona Geology.
Space radar can be used to improve mine safety in underground mines, from EurekAlert!

I could find no reference in the above news release to open-pit mines - I guess we're on our own! Also, the news release mentioned driving the referenced new equipment through mineshafts. Mine shafts are vertical, and no underground trucks or truck drivers drive up and down through these things (shafts). The driving is done in mine tunnels or adits, and in declines or inclines. Declines are mine tunnels or adits that descend gradually as you walk into a mine (or drive - a geologist should be so lucky!); inclines are tunnels that go uphill at a very slight angle as you enter the mine, usually for drainage purposes. Also, the article speaks of the "roofs" of underground mines, a somewhat vague term that could refer to the rocks immediately overhead while underground, or possibly to surface rocks above the entire mine - I'm not really sure which, because if you are in an underground mine, the surface over your head is called the "back." And that's because when the old-timers made their tunnels, they were typically not very high, and the miners had to bend over to enter and walk through them, thus having their backs almost in contact with the "ceiling" of the mine adit.
Last but not least, lots of things have been happening in Arizona - as usual - see these articles and more at Arizona Geology:

• Vale do Rio Doce reported to be looking at Freeport McMoRan Copper & Gold (as a takeover target)
• Freeport is the most likely takeover target
• Drilling is underway at Tombstone
• Why Are So Many Companies investing in Arizona Mines?
• White Cliffs diatomite and zeolites
• Arizona potash looking attractive
• Vale denies takeover plans

Arizona Geology shows a neat, colorful table comparing commodity prices over the past decade, described somewhat more fully at Pitpundit Blog.