Eruption dynamics and petrogenesis of Cerro Las Aguilas rhyolite
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Eruption dynamics and petrogenesis of Cerro Las Aguilas rhyolite dome, petrogenesis of Cerro Pizarro rhyolite dome, and the adventures of Hijo del Santo, Blue Demon, Michael “Miguel el Bravo” Ort, and Francisco “Pancho” Villa; Puebla, Mexico. Matt Schmidt, Spring 2009 Abstract and Introduction Cerro Las Aguilas, is an isolated, rhyolitic dome in the Serdán-Oriental basin in the eastern portion of the Trans-Mexican Volcanic Belt, and, based on the pattern of complexity seen at other nearby domes, is considered unlikely to have a simple evolutionary history. I propose to have someone else map the facies of Las Aguilas, date eruptive events, and analyze the chemistry of erupted products in order to model the petrogenesis and eruptive history of the dome. A second objective of this project is to investigate changes in trace-element chemistry of Cerro Pizarro, located 9 km southeast of Las Aguilas. A comparison of the eruptive histories and chemical characteristics of the two domes may yield important insight into the controlling factors of dome behavior. Background When Nancy Riggs first told me about this master’s project, I didn’t hear anything except “blah blah… project in Mexico… blah.” Last Fall I arranged (with considerable help from others, especially Nancy, Gerardo Carrasco-Núñez, and Ernie, thanks) to spend a semester abroad in Mexico at the Universidad Nacional Autónoma de México in the state of Querétaro. The genius of this plan was convincing everyone that this was indeed a good idea as I will be close to my field area, and that I wasn’t going to Mexico for an extended, slack-off vacation. So far, this plan has worked seamlessly. Statement of Problem Mexico is an amazing country with a very rich history and incredibly diverse cultures, traditions, and landscapes (Lonely Planet’s Mexico, 1995). One could spend their whole life exploring this great country and still know only a small fraction of it. I however must return to the USA in June and see as much as possible before then. To state the obvious, I have no time to squander my days away on a dead, dusty, dinky little dome in the middle of a flat, barely populated, dusty basin. The problem is best summarized as; fieldwork needs to be done for my master’s project but I am not going to do it. The solution The list of things I enjoy about Mexico is exhausting, but of particular interest here are sporting events such as soccer, bullfighting, and especially lucha libre (“free fight” Mexican wrestling). The solution to all my problems was presented to me upon exiting a lucha libre arena after an incredibly over-acted fight. To my astonishment, Blue Demon and Hijo del Santo are not only heroes in the ring but are local petrology heroes-for-hire as well (Fig. 1). Cuando no estoy luchando, estoy ¡Podemos mapear pensando en tu volcán! petrología. Figure 1. The actual poster I found advertising the geological services of Blue Demon (right) and Hijo del Santo (left) (these are their real stage names, I would have thought of better ones). Compare with Figure 2. Los Luchadores Blue Demon and Hijo del Santo (Fig. 1) are among an elite group of luchadores (fighters) who are also well-respected igneous petrologists; the luchapetrologists. All luchadores fight fiercely for their honor and their paychecks. At the end of important matches if the crowd disapproves of the loser’s performance they will ask the winner to remove the loser’s mask. This ritual has parallels in other sports but for a luchador it is the ultimate disgrace. Many people, in envy of the fame and riches enjoyed by petrologists, try to imitate the luchapetrologists. These impersonators, fortunately, are easy to spot due to poor physical condition and the habit of asking stupid questions (Fig. 2). Clearly I have researched this extensively and I can assure the Friday Lunch Clubbe that their money will only go to professionals. ¿¡Donde esta la playa!? Figure 2. Imitation luchadores at the beach, not fit for fighting nor mapping; note the pale, flabby form at extreme right. Compare with Figure 1. It should be noted here that the fate of one of my thesis committee members depends upon the outcome of all this. You may know him as the mild-mannered, soft-spoken, igneous petrologists Dr. Michael Ort, but south of the border he is known as Miguel el Bravo, one of the most brutal luchadores ever known (REALLY need a figure here, does anyone have a photo of him topless that I can mess with in photoshop?). Toro Loco is a new fighter who has been gaining popularity due to his especially cruel and unforgiving tactics (Fig. 3). When Miguel el Bravo returns to Mexico for field studies he will face Toro in a match that will inevitably terminate the loser’s career. As a person, I like Michael and I respect his science but it will be simply unacceptable to have a demasked and disgraced luchador serve on my committee. By forming an alliance with Demon and Santo, Miguel will greatly increase his odds against Toro Loco. Hay espacio en mi sala por tu máscara tambien Dr. Ort. ¡Ha Ha Ha! Figure 3. Toro Loco in his sala de máscaras (hall of masks) sporting his trophy for recent advancements in igneous phase equilibrium. The sala is filled with masks taken from fallen, inferior luchapetrologists. Do not be fooled by his friendly, even inviting, facial expression and body language - this scientist means business (watch out Michael!). Methods In addition to helping Michael keep his honor, Demon and Santo (Fig. 1) will be the principle field and analytical investigators of this project. It would be foolish, however, to leave the two unattended in the field; luchadores are known for quick tempers and time-consuming brawls. A significant amount of field time may be lost due to fighting amongst the investigators if they are left unsupervised. Through the miracle of science, Doroteo Arango Arámbula, better known as Francisco “Pancho” Villa, was resurrected late last year. While there is little work now for revolutionaries, Pancho stays busy as a vigilante with a rifle. He and his horse have agreed to help (without pay) with my thesis work by watching over Demon and Santo and keeping things orderly, peaceful, and productive (typical habits of revolutionaries; Fig. 4). While all this work is taking place, I will be on a lovely, warm, quiet beach somewhere in Mexico (probably Cancún), enjoying not working and many margaritas (see Fig. 2 and imagine me on the beach drinking margaritas without the amateurs present). Upon completion of fieldwork, chemical characteristics will be analyzed and Miguel, Pancho, Demon, and Santo will have fruitful discussions (Fig. 5). Budget Item Cost XRF and ICPMS analysis (10 @ $105/sample) $1,050 Sr/Nd/Pb whole-rock isotopic analysis (6 @ $400/sample) $2,400 40Ar/39Ar dating (2 @ $400/sample) $800 Personal vehicle travel to the beach (3676mi @ $0.445/mi) $1,659 Thin sections (10 @ $10/section) $100 Compensation for Santo and Demon (20 days @ $500/day) $10,000 Pork and beans for Pancho (500 cans @ $1.05/can) $525 Total $16,534 ¡Take that! ¡Ouch! Figure 4. Pancho Villa in action in the field, ready to break up a brawl between the two head field investigators, Demon and Santo. Cerro Pizarro rhyolite dome in the background, note the stern, disapproving look on Villa’s face. Budget justification: This budget is completely justifiable and it is obvious that I need the money (look at the publication year of my guidebook referenced above, it’s way outdated and basically useless but I can’t afford a new one). References Sun, S. and McDonough, W., 1989, Chemical and isotopic systematics of ocean basalts: Implications for mantle compositions and processes, in Saunders, A.D., and Norry, M.J.: Magmatism in the Ocean Basins. Geological Society of London Special Publication 42, p. 313-345.