Hydrothermal alteration and oil show at the Summer Coon intrusive center, Saguache County, Colorado Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/vx021k426

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  • The Summer Coon intrusive center is located seven miles north of Del Norte, Colorado, on the eastern edge of the San Juan Mountains. The intrusive center is the core of a dissected calcalkaline composite volcano of middle Oligocene age. The Summer Coon rocks belong to the Conejos Formation which is the oldest unit in the eastern part of the San Juan volcanic field. The intrusive core is a composite stock of three fine- to mediumgrained rock types. The oldest stock, a texturally inhomogeneous diorite, is cut by numerous radial dikes and is intruded inthe center by a granodiorite porphyry and a rhyolitic vent breccia. The granodiorite porphyry and the vent breccia are part of a 2500-foot diameter central conduit, while the diorite occupies a two mile diameter stock of uncertain origin. Hydrothermal alteration at the Summer Coon intrusive core grades concentrically inward from a propylitic zone to an intermediate argillic zone. The intermediate argillic zone has scattered pods of quartz-sericite and vuggy silica replacement of the host. The zone of intermediate argillic alteration centers on the 2500- foot diameter central conduit and radial dikes of silicic composition. Alteration at the study area was caused by hot spring activity beneath the water table during the fumarolic stage of the volcano. The chemical process of alteration was hydrogen metasomatism, which caused variable hydrolytic decomposition of plagioclase feldspar and mafic minerals leading to the depletion of calcium, magnesium, manganese, nickel, and cobalt in the rocks. Metallization is related to the abundance of pyrite in veinlets and fractures. Centrally located molybdenum and lead anomalies, and weak peripheral zinc anomalies characterize surface geochemistry at the study area. A supergene oxidized cap zone 35 feet thick has created a superimposed effect upon hypogene alteration, and the more mobile elements have been leached from it. The favorable aspects of the Summer Coon intrusive area as a porphyry copper-molybdenum exploration target include the existence of a composite stock with concentric zonation of hydrothermal alteration assemblages, and centrally located molybdenum, lead, and IP anomalies, low resistivity, and low magnetic value zones. Unfavorable aspects include the lack of structures, the lack of peripheral lead, zinc, silver, and gold mineralization, and the great depth at which hypothetical zones of intense hydrothermal alteration and mineralization may be located. Tarry brownish-black petroleum was present in pyrite-coated fractures in cores from three diamond-drill holes. The petroleum was dated and is interpreted to have been locally generated from Cretaceous source rocks and to have migrated into the intrusive core after the cessation of hydrothermal activity.
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  • ScandAll PRO 1.8.1 on a Fi-6770A in PDF format. CVista PdfCompressor 5.0 was used for pdf compression and textual OCR. Plates: Master file scanned at 600 dpi (8-bit grayscale) using SlmartLF 1.3.05 on a Paradigm ImagePRO GxT 42 HD (OEM version of ColortracSmartLF Bx 42). Image manipulated by SmartLF1.3.05.
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  • description.provenance : Submitted by Kirsten Clark (kcscannerosu@gmail.com) on 2013-08-19T23:49:35Z No. of bitstreams: 7 LokenTrygve1983.pdf: 3001385 bytes, checksum: 92cccea1bf3ee2e67ae602c5796d82bd (MD5) Plate 1.jpg: 2622276 bytes, checksum: 560abaa64839fc8221688f6fd6211111 (MD5) Plate 2.jpg: 2357293 bytes, checksum: 78d313799334bcc8a6984c48bc1a9853 (MD5) Plate 3.jpg: 698535 bytes, checksum: c66c99becdf824481c2a8fcfac6e031e (MD5) Plate 4.jpg: 901444 bytes, checksum: 5e6e1bda0974c41bc82d1fc4b1fedd38 (MD5) Plate 5.jpg: 709666 bytes, checksum: d97001a67eb67fc8b417f52d2fd1820b (MD5) Plate 6.jpg: 703400 bytes, checksum: 9789afe21d93785c5d12de57cab30dc6 (MD5)
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  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-08-20T17:17:57Z (GMT) No. of bitstreams: 7 LokenTrygve1983.pdf: 3001385 bytes, checksum: 92cccea1bf3ee2e67ae602c5796d82bd (MD5) Plate 1.jpg: 2622276 bytes, checksum: 560abaa64839fc8221688f6fd6211111 (MD5) Plate 2.jpg: 2357293 bytes, checksum: 78d313799334bcc8a6984c48bc1a9853 (MD5) Plate 3.jpg: 698535 bytes, checksum: c66c99becdf824481c2a8fcfac6e031e (MD5) Plate 4.jpg: 901444 bytes, checksum: 5e6e1bda0974c41bc82d1fc4b1fedd38 (MD5) Plate 5.jpg: 709666 bytes, checksum: d97001a67eb67fc8b417f52d2fd1820b (MD5) Plate 6.jpg: 703400 bytes, checksum: 9789afe21d93785c5d12de57cab30dc6 (MD5)
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-08-20T00:31:15Z (GMT) No. of bitstreams: 7 LokenTrygve1983.pdf: 3001385 bytes, checksum: 92cccea1bf3ee2e67ae602c5796d82bd (MD5) Plate 1.jpg: 2622276 bytes, checksum: 560abaa64839fc8221688f6fd6211111 (MD5) Plate 2.jpg: 2357293 bytes, checksum: 78d313799334bcc8a6984c48bc1a9853 (MD5) Plate 3.jpg: 698535 bytes, checksum: c66c99becdf824481c2a8fcfac6e031e (MD5) Plate 4.jpg: 901444 bytes, checksum: 5e6e1bda0974c41bc82d1fc4b1fedd38 (MD5) Plate 5.jpg: 709666 bytes, checksum: d97001a67eb67fc8b417f52d2fd1820b (MD5) Plate 6.jpg: 703400 bytes, checksum: 9789afe21d93785c5d12de57cab30dc6 (MD5)
  • description.provenance : Made available in DSpace on 2013-08-20T17:17:57Z (GMT). No. of bitstreams: 7 LokenTrygve1983.pdf: 3001385 bytes, checksum: 92cccea1bf3ee2e67ae602c5796d82bd (MD5) Plate 1.jpg: 2622276 bytes, checksum: 560abaa64839fc8221688f6fd6211111 (MD5) Plate 2.jpg: 2357293 bytes, checksum: 78d313799334bcc8a6984c48bc1a9853 (MD5) Plate 3.jpg: 698535 bytes, checksum: c66c99becdf824481c2a8fcfac6e031e (MD5) Plate 4.jpg: 901444 bytes, checksum: 5e6e1bda0974c41bc82d1fc4b1fedd38 (MD5) Plate 5.jpg: 709666 bytes, checksum: d97001a67eb67fc8b417f52d2fd1820b (MD5) Plate 6.jpg: 703400 bytes, checksum: 9789afe21d93785c5d12de57cab30dc6 (MD5) Previous issue date: 1982-12-06

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