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EVOLUTION OF UPPER CRUSTAL MAGMATIC PLUMBING SYSTEMS:
COMPARISONS OF GEOCHRONOLOGICAL, PETROLOGICAL, GEOCHEMICAL
AND STRUCTURAL RECORDS IN THE CRETACEOUS FANGSHAN PLUTON,
BEIJING, CHINA, THE MESOZOIC CENTRAL SIERRA ARC, CA, USA AND THE
MIOCENE SILVER CREEK CALDERA, AZ, USA
by
Tao Zhang
A Dissertation Presented to the
FALCULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(GEOLOGICAL SCIENCES)
May 2012
Copyright 2012 Tao Zhang
Object Description
| Title | Evolution of upper crustal magmatic plumbing systems: comparisons of geochronological, petrological, geochemical and structural records in the Cretaceous Fangshan pluton, Beijing, China, the Mesozoic central Sierra arc, CA, USA and the Miocene Silver Creek caldera, AZ, USA |
| Author | Zhang, Tao |
| Author email | taozhang@usc.edu;taohsu@me.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Geological Sciences |
| School | College of Letters, Arts And Sciences |
| Date defended/completed | 2012-03-28 |
| Date submitted | 2012-05-04 |
| Date approved | 2012-05-04 |
| Restricted until | 2012-05-04 |
| Date published | 2012-05-04 |
| Advisor (committee chair) | Paterson, Scott |
| Advisor (committee member) |
Lund, Steve McCann, Edwin |
| Abstract | Magmatism is the most important process to form crust in Earth’s history. Both volcanic and plutonic rocks are major components of Earth’s current crust and their geochronologic, geochemical and structural features provide key information for rock sequence, source reservoirs, tectonic environments and emplacement mechanisms of igneous rocks. In order to better picture the igneous rocks as a whole I picked three upper crustal magmatic systems in different tectonic environments to study. Fangshan pluton is an intraplate pluton that emplaced at the depth of about 10-15; Central Sierra plutons and correlated volcanic rocks are subduction related magmatism with the plutons emplaced at about the same depth as Fangshan; Silver Creek caldera is a much shallower magmatic system with intralcaldera tuff and subvolcanic plutons. High-precision CA-TIMS (chemical abrasion thermal ionization mass spectrometer) geochronology of Fangshan pluton rocks indicated a much longer history of the magmatic system below the pluton than what people realized before. The existence of antecrystic zircons shows the intense recycling of crystals by multiple magma pulses. The same technique was used on Silver Creek plutonic and volcanic rocks. No antecrystic zircons have been found so far in both the volcanic and subvolcanic plutons, which indicates a relatively simpler history for this magmatic system and the existence of possible filtering mechanisms of older zircons. Considering all single zircon ages from oldest to youngest, the lifespan of this system is only about 1.5 m.y. that is a lot shorter than those deeper magmatic systems. Regional geochemistry study done on the Central Sierra Mesozoic igneous rocks show a close link between the two rock types and the important roles magma fractionation, mixing and mingling played during the formation of these magma bodies. The magma source below this area did not change much through the whole Mesozoic though. In order to see the rock fabrics in Silver Creek caldera, AMS study was carried on for 23 samples from this caldera. The results show extremely weak fabrics in both shallow intrusions and volcanic rocks. Although the randomly oriented magnetic lineations in the intracaldera tuff can’t be well connected with the outflow magnetic lineations, it does agrees well with the typical caldera forming model of mechanically collapsing of the magma chamber roof after the chamber drained. Magnetic fabrics in the plutonic rocks do not form any noticeable pattern. More data need to be collected to make sure whether there is pattern or not. Multiple data sets from different magmatic systems do show the complications involved in this process and correlated study of both plutonic and volcanic rocks of the same system is a powerful way to understand any single magma plumbing system. There is still some fundamental difference between the plutonic and volcanic rocks, so the correlation of them needs careful evaluations still. |
| Keyword | magma;U/Pb geochronology; AMS study; geochemistry; plutonic-volcanic connection |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m |
| Rights | Zhang, Tao |
| Access conditions | The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given. |
| Repository name | University of Southern California Digital Library |
| Repository address | USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA |
| Repository email | cisadmin@usc.edu |
| Archival file | uscthesesreloadpub_Volume4/etd-ZhangTao-751.pdf |
Description
| Title | Page 1 |
| Full text | EVOLUTION OF UPPER CRUSTAL MAGMATIC PLUMBING SYSTEMS: COMPARISONS OF GEOCHRONOLOGICAL, PETROLOGICAL, GEOCHEMICAL AND STRUCTURAL RECORDS IN THE CRETACEOUS FANGSHAN PLUTON, BEIJING, CHINA, THE MESOZOIC CENTRAL SIERRA ARC, CA, USA AND THE MIOCENE SILVER CREEK CALDERA, AZ, USA by Tao Zhang A Dissertation Presented to the FALCULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (GEOLOGICAL SCIENCES) May 2012 Copyright 2012 Tao Zhang |
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