Sunday, September 21, 2008

A Geology Dream: Synclines

I had a dream last night, among a couple others that I don't remember too well, about synclines. In it a VIP-type boss, an old colleague and mentor of mine who has sometimes shown up in other dreams, was told about a recent report, in which I mentioned a syncline-type model for gold exploration. He exclaimed in a loud, booming voice, "Syncline! Surely you mean anticline!"

Anticlines are quite common exploration targets for Carlin-type disseminated low-grade gold deposits in Nevada. The anticlines, whether or not they have something genetic to do with the actual ore deposition, expose the lower plate of the Roberts Mountains Thrust, a late Devonian to Mississippian (mid-Paleozoic) thrust fault from the Antler Orogeny (about 340-380 million years in age), which generally places western-facies siliceous rocks like cherts and shales over eastern-facies carbonate rocks like silty limestones. It often places Ordovician Vinini or Valmy Formation cherts and shales over Silurian-Devonian Roberts Mountains Formation and Hanson Creek Formation limestones and silty, shaly limestones. The introduction of gold into these lower plate rocks is generally thought to have taken place during the early Tertiary (or Paleogene), maybe about 42 to 46 million years ago, long long after the above Paleozoic rocks (Ordovician, Silurian, and Devonian) were deposited in an ocean off the shore of a much smaller-than-now western America.

My dream, nevertheless, was about a gold model wherein the gold is deposited in synclines, in the upper plate of silicified, jasperoidal low-angle faults, which have commonly been thought to be thrust faults of Jurassic(?) age, but which nevertheless sometimes and in some areas, place younger rocks on top of older rocks, a red flag suggesting that the low-angle faults in question could be extensional in origin and possibly much, much younger, even Tertiary.

In the dream, after the VIP-geologist pronounced his shock about syncline-type gold, I came into the picture, saying that I would be glad to explain the model. Somehow, though, it was difficult to do, either because I couldn't find the report with the pertinent cross-sections and diagrams, or because the office area was too barren of papers, or because the other geologist was too dis-inclined to listen [dis-synclined? - he did diss the syncline!].

It was kind of annoying in the dream, the way not being listened to often is - but it was also annoying upon awakening, in that I had a difficult time telling the dream from reality, because the details of place and people were similar to everyday reality.

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