Thursday, September 22, 2011

Field Trip Report: Locked Out while Looking at Breccia

It was about a million years ago during the first couple years of my field geology experience, probably toward the end of a summer or maybe it was early fall. A field trip was concocted to show some of the immediate mucky muck types around a property I'd come to call my own — a huge claim block centered on one of the major Tertiary calderas (Tertiary then, Paleogene now) of central Nevada — although I wasn't on the ground or anywhere near it when the discovery was made (nor was I there when the caldera formed way back in the early Oligocene). The guys (all guys except for me) were mucky mucks to me at the time, although at least a few of them probably didn't think of themselves that way: my boss, my boss's boss, and some new guy with distinct mucky muck potential who would later go on to run exploration departments and such.

We drove up the main dirt road, with me leading in my burgundy Bronco, a company truck that had been assigned to me that year. At least one other field vehicle was following me, maybe two or three. The truth is, I ran more than one field trip up that same canyon over the course of three or four years, showing various people around the area for various reasons, and the many field trips blend together in my mind. Consequently, I don't remember exactly who was on which field trip, save for a key few people on a few key trips.

I was nervous; maybe the boss was riding with me, perhaps he was in his "Boss Mobile" (not exactly the phrase we used) behind me. I didn't want to go too fast or too slow. I didn't want to hit rocks or ruts, I didn't want to slide sideways around curves or in any other way look like a foolish or inexperienced young geologist.

I slowed down as the caravan I was leading approached our area of particular interest: a volcanic breccia, possibly a breccia pipe. I pulled over to the left side of the road; everyone else pulled in behind me. At that point, we all jumped out of our various vehicles, suited up with Filson vests (if we didn't already have them on), grabbed rock hammers from beneath seats or from backs of trucks, and crossed the main wash northward over to the cliffy bluffs exposing the breccia. It was quite an enlightening field trip for me, with lots of proclamations made about what should be found in breccia pipes as opposed to flow breccias, and gradually some determinations were forthcoming. The matrix of the breccia, highly siliceous, dark, and very fine-grained, was hot when the breccia formed. It had plastered itself onto the breccia fragments such that one could hardly separate fragment from matrix. Some possible sedimentation in the upper part of the main exposure was noted, leading thoughts towards more than one eruptive or explosive event, with some settling downward into the proposed pipe. Flows going outward from the vent or pipe were identified; a thick flow breccia near the vent thinned laterally to one main one and a couple or a few thin ones above it.

Samples were grabbed: hand samples of one of the best breccias in the world (well, in Nevada at least). Everyone wanted a large chunk of the breccia matrix, which contained small chunks of fragments grading downward to rock flour. Large chunks of matrix were hard to come by: all large chunks, when broken, revealed giant fragments only thinly coated with matrix. I'll dig up some pictures sometime, although my memory is much better than the pictures I took a couple years back, or maybe all the best samples are in personal collections made that day, or housed in unknown warehouses.

We walked back to the trucks. Oops! I had left the keys to my Bronco in the ignition and had locked the doors. (Many field trucks are left with keys in ignitions, windows rolled down, and doors unlocked just to prevent this type of occurrence, and because dirt roads in Nevada are generally considered safe, or were back then, from truck stealing.) I was quite flustered and embarrassed, and it looked like the boss thought I was a complete idiot. The new guy, who would become a longtime friend and colleague, and later an exploration manager, immediately started looking around the side of the road and wash area and, voila!, came up with some sturdy wire. Without saying a word, he walked over, bent the wire into the right shape, slipped it under the rubber of the driver's side wind wing, hooked it over the little metal pin that was designed to be used to open and close the wind wing from the inside, and pulled hard. That broke the mechanism that would keep the wind wing shut and in a "locked" position. The door handle or window crank could then be accessed; the the door was unlocked and opened.

Busting the wind wing locking pin made it impossible to get locked out ever again. One or two of the field trip participants admitted it was one of the first thing they would do upon getting a new vehicle: bust the wind wing locking mechanism. We don't have wind wings on trucks anymore for that very reason.

It was a lesson I never forgot: I sometimes busted the wind wing pin on new company trucks preemptively, even though I'm not prone to leaving keys in ignitions, and I always had sturdy wire easily accessible in the back of the truck. And yes, I have used that trick at least one or two other times, whether on my truck or on someone else's.

Related Posts:
Friday Field Photos #3
In the Field
Friday Field Photo #4
Drilling Stories: Getting Started at Northumberland
The Unlikely Gradational Stratigraphy


Anonymous said...


The sliding rear windows of some pickup trucks were also a godsend to locked-out drivers (and car thieves, of course); the gap between the panes was on a direct line with the door lock knob.

"we all jumped out of our various vehicles...grabbed rock hammers from beneath seats or from backs of trucks..." Apparently that's something else that's changed on some company field trips. One of my oil company clients lamented to me about a company field trip to the western US where only one person in the group was allowed to carry a rock hammer. If someone wanted a sample, they had to have a safety meeting and discuss possible alternatives to using the hammer to get a sample. Then the designated risk-taker would approach the exposure while the rest (all wearing safety glasses, of course), would back off to a safe distance while the sample was procured. Yeccch--give me strength!


Silver Fox said...

Howard, I haven't heard of any mining companies going for "designated sampler" status for anyone so far, whether at work or on field trips. Sounds ridiculous.