PETROLOGIC AND GEOCHEMICAL ANALYSIS OF INTERMEDIATE TO MAFIC MAGNETITE-BEARING VOLCANIC FLOWS AND ASSOCIATED DIKES IN THE KNIGHT RANGE, GRANT COUNTY, NEW MEXICO

<p>The Knight Range of southwestern Grant County, New Mexico, is made up of a northeast-dipping package of Cretaceous-Tertiary volcanic, volcaniclastic, and sedimentary units. It is located in the Burro Uplift, south of the Tyrone mining district, at the intersection of the Mogollon-Datil volcanic field and the southern Basin and Range province. This package of supracrustal rocks unconformably overlies the Mesoproterozoic Burro Mountain Granite, which is intruded by Proterozoic diabase dikes that contain ~12% magnetite. Important to this study are the Tertiary intermediate to mafic volcanic rocks and dikes in this package that are magnetite-bearing. Field work was initiated to investigate significant volumes of previously unreported magnetite in these Tertiary units and to investigate spatial and genetic relationships between the units. New field observations include 1) a previously unmapped dike that cross-cuts the Cretaceous-Tertiary Conglomeratic Sandstone of Knight Canyon and 2) previously unreported magnetite in two mapped units (the JPM Mountain Andesite; the Malpais Latite and Andesite). In these units, magnetite is disseminated and found in a foliated texture in areas of presumed fluid alteration near joints.</p> <p>Samples of the Proterozoic diabase dikes, the JPB Mountain Andesite, the Malpais Latite, and Andesite, and the Juniper dike were made into polished thin sections for detailed petrographic analysis and powdered and analyzed using a handheld XRF(hXRF) to determine bulk composition. The Proterozoic dikes are mafic to ultramafic basalts that vary from picrobasalt to foidite; they are alkaline and tholeiitic. The JPB Mountain Andesite, the Malpais Latite and Andesite, and the Juniper dike all have intermediate compositions ranging from basaltic trachyandesite to andesite; they are subalkaline and calc-alkaline. Their bulk geochemistry does not imply a genetic relationship between the Proterozoic diabase dikes with the Tertiary units. The andesitic units and the Juniper dike have similar mineralogy, textures, and geochemistry. However, the TAS diagram shows more similarity between the JPB Mountain Andesite and the Juniper whereas the AFM diagram shows more similarity between the Latite and Andesite of Malpais Hill to the Juniper dike. Therefore, a study of the genetic relationship between the JPB Mountain Andesite and/or the Malpais Latite and Andesite to the Juniper dike is inconclusive. While both andesitic units are classified as andesite, the Malpais Latite and Andesite are dominantly basaltic andesite. Due to petrologic and geochemical similarities, these units may share a magma source but tell different stories about the evolution of the magmatic system that produced these Tertiary units and dikes.</p>

Name thesis:degree_name

Master of Science - Geology

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Geology

Year dc:date.available

2024

Author dc:creator

• Campos, Marykathryn

Contributors dc:contributor

• Liane M. Stevens
• Julie Bloxson
• R. LaRell Nielson

• Geology
• Volcanology
• Igneous Petrology
• Petrology
• New Mexico
• Knight Range
• Andesite
• Magnetite
• XRF
• Ignimbrite Flareup

Repository record dc:identifier

https://scholarworks.sfasu.edu/etds/589

OAI identifier oai:identifier

oai:scholarworks.sfasu.edu:etds-1630