Eruption dynamics and petrogenesis of Cerro Las Aguilas rhyolite by fiw10869


									 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.

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


esta la

    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

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!).

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).

                        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!


      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).


      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.

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