Florida Mountains Intrusion: A Study of Magmatic Processes and Tectonic Setting, Study Guides, Projects, Research of Petrology

Download Florida Mountains Intrusion: A Study of Magmatic Processes and Tectonic Setting and more Study Guides, Projects, Research Petrology in PDF only on Docsity! GEOL 399 Fall 2006 PROJECT TWO Florida Mountains Intrusion (90 points) Due 10:30 a.m., Friday, 3 November 2006 The southern half of the Florida Mountains south of Deming, New Mexico, comprises the Florida Mountains intrusion, dated by U-Pb on zircons at 513 + 10 Ma. The age and geochemistry of these rocks are very interesting and more than a little controversial! At the time of emplacement (Latest Cambrian-Early Ordovician), southern New Mexico is supposed to have been a passive continental margin formed by the rifting of the Laurentian plate. Several aulacogens, or fossil continental rifts, extend into the western or North American side of the passive margin, but most geologists do not place an aulocogen in the New Mexico region. The presence of the Florida Mountains intrusion and other similar intrusions, including carbonatites, throughout New Mexico suggest that a continental rift developed and produced rift magmas. The other interesting feature of the Floridas Mountains intrusion is its relationship with the overlying Lower Ordovician Bliss Sandstone. The Bliss Sandstone, which has been interpreted as a sheet of deltaic sands deposited on the passive margin, nonconformably overlies the intrusion and, in the Florida Mountains, is derived from the intrusion. The timing of intrusion (513 + 10 Ma), cooling (491 + 5 Ma), and deposition of the Bliss Sandstone (ca. 480 Ma) implies rapid erosion and unroofing of the pluton. Thus, one of the important questions in this project is the depth of intrusion. If the pluton crystallized in the lower crust, at approximately 30 km depth, then uplift rates were about 1.36 km/Ma (that's 1.36 m every thousand years or 1.36 mm every year!). But if the pluton was very shallow, perhaps at 2 km, uplift rates were only about 0.09 km/Ma (or 0.09 mm every year—that’s pretty slow!). That’s a big difference, so it is important to look for any mineralogic, geochemical, or textural clues for the depth of crystallization. Samples 595GR106 silicic hand specimen and thin section 595GR108 silicic hand specimen and thin section 595SY110 hand specimen almost all silicic; both silicic and mafic in thin section 595SY113 hand specimen is silicic; both silicic and mafic in thin section 995SY114 silicic hand specimen and thin section 995SY115 silicic hand specimen and thin section 995GR116 silicic hand specimen and thin section 995GR118 mafic and silicic hand specimens and thin sections 995GR119 mafic and silicic hand specimens and thin sections 995GR120 mafic and silicic hand specimens and thin sections 1095GR121 silicic hand specimen and thin section 1095GR123 mafic hand specimen and thin section 1095GR127 silicic hand specimen and thin section 1 Assignment Write a report, due at 10:30 a.m., Friday, 3 November 2006, on the mineralogy, geochemistry, fractionation, geologic history, and tectonic history of the Florida Mountains Intrusion. You are given hand samples, thin sections, major and trace element geochemistry, and we will visit the pluton on a field trip. 2 samples (10 points) 10/20 Major and trace element geochemical diagrams with a full credit (10 points) microtheme that : 1) describes the data, and 2) interprets if timely & complete. the data. In this little paper, you will place the samples You will also receive in evolutionary order and discuss the relationship between my written response. the degree of fractionation and the mineralogy. You will also discuss the tectonic setting of the intrusion, based on your interpretation of the trace element data. The first paragraph should describe the data; the second should interpret. 10/27 The rough draft of your paper. full credit (10 points) if timely & complete. I will not give you a written response. 10/27 Participation in peer review of your classmates’ papers. 5 points each for You will review two rough drafts in class. reviews of two papers 11/3 Final draft due. You must turn in the following: Your paper will be -your final draft graded holistically, -two peer reviews of your paper based on the criteria listed below. (50 pts.) 5 Evaluation Criteria Content of the paper Paper presents the following data: mineralogy, modes, major element, and trace element data for 13 samples The 13 samples are classified using a modal classification system Chemical analyses are used to discuss the tectonic setting of the pluton Chemical and modal data are used to discuss fractionation processes Modal, textural, and/or chemical data are used to estimate the depth of intrusion Geologic cross-section is provided Geologic history of the intrusion is discussed Technical aspects of the paper Writer describes the relationships within the data set, including mineralogy, modes, major elements, and trace elements. Writer supports interpretations using data and diagrams. Interpretations reflect clarity of thought and depth of analysis. Discussion section used the interpretations to address broader issues. Summary section provides a quick overview of interpretations and implications. Abstract provides data and conclusions. Standard edited English is used effectively. Writing process Revision is based on instructor responses to microthemes. Revision is based on peer reviews. Paper has been edited and proofread. REFERENCES: Clemons, R.E., 1983, Geology of Gym Peak Quadrangle, Luna County, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Geologic Map 58. Evans, K.V., and Clemons, R.E., 1988, Cambrian-Ordovician (500 Ma) Alkalic Plutonism in Southwestern New Mexico: U-Th-Pb Isotopic Data from the Florida Mountains: American Journal of Science, V. 288, p. 735-755. GEOL 399 Igneous and Metamorphic Petrology Fall 2006 Project Two: Evaluation Criteria Evaluation by Dr. McMillan Content of the paper _____ Paper presents the following data: mineralogy, modes, major element, and trace element data for 13 samples _____ The 13 samples are classified using a modal classification system _____ Chemical analyses are used to discuss the tectonic setting of the pluton _____ Chemical and modal data are used to discuss fractionation processes _____ Modal, textural, and/or chemical data are used to estimate the depth of intrusion _____ Geologic cross-section is provided _____ Geologic history of the intrusion is discussed Technical aspects of the paper _____ Writer describes the relationships within the data set, including mineralogy, modes, major elements, and trace elements _____ Writer supports interpretations using data and diagrams _____ Interpretations reflect clarity of thought and depth of analysis _____ Discussion section used the interpretations to address broader issues _____ Summary section provides a quick overview of interpretations and implications _____ Abstract provides data and conclusions _____ Standard edited English is used effectively Writing process _____ Revision is based on instructor responses to microthemes _____ Revision is based on peer reviews _____ Paper has been edited and proofread Holistic summary score: _____ Letter grade: _____ Points: _____ * * * * * * * * * * * * Project grade Mineralogy and modes _____/10 Microtheme _____/10 Rough draft _____/10 Peer review _____/10 Paper _____/50 Total _____/90 GEOL 339