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The Research and Scholarship Symposium The 2016 yS mposium

Apr 20th, 11:00 AM - 2:00 PM The etrP ology and Geochemistry of the Independence Swarm, Owen’s Valley, California Sean B. O'Donnell Cedarville University, [email protected]

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O'Donnell, Sean B., "The eP trology and Geochemistry of the Independence Dike Swarm, Owen’s Valley, California" (2016). The Research and Scholarship Symposium. 18. http://digitalcommons.cedarville.edu/research_scholarship_symposium/2016/poster_presentations/18

This Poster is brought to you for free and open access by DigitalCommons@Cedarville, a service of the Centennial Library. It has been accepted for inclusion in The Research and Scholarship Symposium by an authorized administrator of DigitalCommons@Cedarville. For more information, please contact [email protected]. The Petrology and Geochemistry of the Independence Dike Swarm, Owen’s Valley, California Sean B. O’Donnell, Cedarville University Department of Science and Mathematics, 251 N. Main St. Cedarville, OH 45314, [email protected] Abstract Petrography Petrologic studies are important because they provide insights into the condi- tions under which rocks form. The Late Jurassic Independence Dike Swarm is a D D series of vertical igneous dikes that crop out in eastern and southern California, and range from mac to felsic in composition. In order to examine their petrol- ogy and geochemistry, surface samples were collected from four di erent dike P P outcrops within Owen’s Valley, CA. The samples were examined through thin-section analysis under a petrographic microscope, X-ray di raction analy- sis, and X-ray uorescence analysis. Mineral composition, mineral size, major, D D trace, and rare element concentrations were collected from these analy- ses. Results from all samples were compared. Petrologically, the dikes range in IDS 1 PP IDS 1 XP classication from gabbro to diorite to granite, with the more gabbroic and di- oritic dikes having larger concentrations of plagioclase. The more granitic dikes have larger concentrations of quartz and potassium feldspars. There is consid- erable mineral alteration, especially among the feldspars, with some of the K K samples having been almost completely altered into clay minerals. The pres- ence of epidosite within a dike suggests the source incorporated coun- try rock on the way toward the surface. Geochemical analysis shows chemical K K variability among the dikes and possible source magma di erentiation within the Owen’s Valley area. Q Q Geochemical Data IDS 2 PP IDS 2 XP Background Alkali v Silica (Middlemost 1994) QAPF diagram - Si oversaturated Tawite/Urtite/Italite Q

1 - alkali-feldspar quartzolite syenite The Independence Dike Swarm (IDS) is a series of vertical igneous dikes that 15 IDS-2 Foid 2 - monzodiorite syenite P monzogabbro outcrop in Owen’s Valley, the Sierra , Inyo Range, Argus Range, and quartz-rich Foidolite Foid 3 - diorite, gabbro granitoid monzo- Syenite

O syenite F 2 10 F K Mojave Desert in southeastern California. The dike swarm has north-south Foid monzo-gabbro Quartz P O 2 monzonite F F a Monzonite 1DS-4 N monzo- Monzo grano- length of almost 250 km, and an east-west length of about 40 km. The dikes Foid 1DS-3 syeno- granite tonalite gabbro diorite Monzo- granite diorite gabbro Granite 5 1DS-1 alk-fsp.granite IDS-4 1DS-2 Granodiorite IDS-6 q-diorite diorite q-alk-fsp quartz- IDS-5 Gabbroic

Diorite q-gabbro above the surface. Most of the dikes in the swarm have been repeatedly Gabbro syenite syenite quartz- IDS-3

gabbro q-anorthosite Peridot Quartzolite monzonite q-monzodiorite

0 q-monzogabbro 1 syenite monzonite 2 3 IDS-1 A P dated to 148 Ma in the Late Jurassic Period, and a few have been dated to 40 50 60 70 80 90 the Mid-Cretaceous. Owens Valley is a structural trough that formed as a SiO2 graben, and stretches from Mono Lake in the north, all the way to the Coso IDS 3 PP IDS 3 XP SiO2 v Major Elements (weight %) 1DS-2 1DS-1 Range in the south. 1DS-1 1DS-2 1DS-1

1DS-3 3

2 1DS-2 1DS-3 O 2 1DS-3 TiO MgO Al 1DS-1 1DS-2 O 1DS-4 1DS-4 1DS-4 O 0.0 0.5 1.0 1.5 2.0 12 14 16 18 20 22 24 0 2 4 6 8 10 50 55 60 65 70 75 50 55 60 65 70 75 50 55 60 65 70 75 1DS-2

SiO2 SiO2 SiO2

1DS-1 1DS-3 1DS-4 Methods 1DS-3 1DS-1 1DS-4 O O 2 2 K CaO Na 1DS-3

1DS-2 1DS-2 P 1DS-2 1DS-4 1DS-1 - P 0 2 4 6 8 10 0.5 1.5 2.5 3.5 1 2 3 4 5 6 Q 50 55 60 65 70 75 50 55 60 65 70 75 50 55 60 65 70 75 Q SiO SiO SiO crops of the Independence Dike Swarm in Owens Valley, CA (IDS 1 - 2 2 2 IDS 8). From these samples thin sections were made and X-Ray Dif- 1DS-1 5

O 1DS-3 2 P fraction analysis was run by Calgary Rock and Materials Services Inc. 1DS-2 1DS-4 IDS 4 PP IDS 4 XP 0.0 0.2 0.4 0.6 0.8 1.0 in Calgary, AB. X-Ray Fluorescence analysis was performed at Texas 50 55 60 65 70 75

SiO2 Tech University for major, trace, and rare earth element concentra- MgO v Major Elements (weight %) 1DS-2 1DS-4 tions in IDS 1, IDS 2, IDS 3, and IDS 4. Petrographic analysis was per- 1DS-1 1DS-3 3 2

2 1DS-3

1DS-2 O 2 SiO TiO P P Al formed on the thin sections using a Nikon Eclipse 50i Pol micro- 1DS-2 1DS-1 1DS-3 1DS-4 1DS-1 1DS-4 scope and Br computer software. The thin section analysis consist- 45 55 65 75 0.0 0.5 1.0 1.5 2.0 12 14 16 18 20 22 24 0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10 ed of measuring and recording crystal sizes, the orientation of pla- Q O MgO MgO MgO 1DS-3 1DS-4 1DS-1 O 1DS-3 1DS-4 1DS-1 O O gioclase phenocrysts, and point counting of mineral types. For the Q 2 2 K CaO Na 1DS-3 point counting, each slide was dividing into a 4x6 grid of squares 1DS-2 1DS-2 1DS-2 1DS-4 1DS-1 0 2 4 6 8 10 0.5 1.5 2.5 3.5 1 2 3 4 5 6

0 2 4 6 8 10 0 2 4 6 8 10 0 2 4 6 8 10

MgO MgO MgO to perform point counting on. In each square a grid was overlaid in 1DS-1 5

O 1DS-3 2 the computer software which consisted of 35 crosshairs, and the P IDS 5 PP IDS 5 XP 1DS-2

1DS-4 mineral at each of these crosshairs was recorded, making for 350 0.0 0.2 0.4 0.6 0.8 1.0 0 2 4 6 8 10

MgO points counted on each slide. P P SiO v Trace Elements (weight %) Q 2 Q 1DS-1 1DS-1 1DS-2 1DS-1

1DS-3 1DS-3 Sr Zr Ba 1DS-3

1DS-2 1DS-2 1DS-4 1DS-4 1DS-4 0 400 800 1200 400 600 800 1200 100 140 180 220 Discussion O 50 55 60 65 70 75 50 55 60 65 70 75 50 55 60 65 70 75 O SiO SiO SiO 2 2 2

1DS-1 1DS-1 1DS-2 1DS-4 O The di erent dikes of the Independence Dike Swarm within Owen’s Valley 1DS-2 2 Na Ni Cr O 2

1DS-2 K are compisitionally di erent from each other. IDS 1 is gabbro, the most 1DS-3 1DS-3 1DS-3 1DS-4 1DS-4 1DS-1 0 50 100 200 300 0 50 100 200 300 0.5 1.0 1.5 2.0 2.5 mac dike of the four sampled. IDS 2 is mineralogically a granitoid, but 50 55 60 65 70 75 50 55 60 65 70 75 50 55 60 65 70 75 SiO2 SiO2 SiO2

1DS-3 1DS-3 1DS-3 chemically it is a diorite. The di erence is due to the large amounts of min- IDS 6 PP IDS 6 XP 1DS-1 1DS-2 V Zn eral alteration that has taken place with the dike. Most of the feldspars Cu 1DS-1 1DS-1 1DS-2 1DS-4 1DS-4 1DS-4 1DS-2 have been altered to clay minerals, however, much of the original chemical 0 20 40 60 80 100 0 50 100 150 200 250 0 50 100 150 200 50 55 60 65 70 75 50 55 60 65 70 75 50 55 60 65 70 75 compositon is still present. The quartz/feldspar concentration is therefore SiO2 SiO2 SiO2 relatively high compared to the amount silica in the rock. IDS 3 and IDS 6 monzodiorites, and the dikes at IDS 4 for are granites. IDS 4 has the highest E E silica concentration of all the dikes sampled. The chemical data shows wide Acknowledgements variability between all the dikes Owen’s Valley. This is evidence of possible Q I would like to thank Mr. Raymond Strom and Calgary Rock and Materials source magma di erentiation, but the data is not conclusive. Also, in IDS 3, Q Services for their work in preparing thin sections and performing XRD anal- epidosite inclusions were found, meaning that the source magma incorpo- ysis, as well as Dr. Melanie Barnes and Texas Tech University for performing rated country rock on the way to the surface. IDS 7 PP IDS 7 XP XRF analysis.