Cone sheet
A cone sheet is a type of high-level igneous intrusion found in partly eroded central volcanic complexes. Cone sheets are relatively thin inclined sheets, generally just a few metres thick, with the geometry of a downward-pointing cone. Viewed from above, their outcrop is typically circular to elliptical. They were originally described from the Ardnamurchan, Mull and other central complexes of the British Tertiary Volcanic Province (now recognised as part of the North Atlantic Igneous Province).
Occurrence
Cone sheets are widely distributed at the lower levels of volcanic complexes.
| Name | Location | Age | Dominant rock type | Reference |
|---|---|---|---|---|
| Ardnamurchan | Scotland | Paleogene | dolerite | |
| Tejeda | Gran Canaria | Miocene | trachyte, phonolite | [1] |
| Jabal Arknu | Libya | Tertiary | [2] | |
| Otoge | Japan | Miocene | [3] | |
| Zarza | Mexico | Cretaceous | gabbro | [4] |
| Houshihushan | China | Cretaceous | granite porphyry | [5] |
| Boa Vista | Cape Verde | Miocene | phonolite | [6] |
Formation
Soon after cone sheets were first described, their formation was explained in terms of intrusion along conical fractures extending from the top of an intrusive body into the overlying rocks, caused by high magmatic pressure.[7]
References
- ↑ Donoghue, Eleanor; Troll, Valentin R.; Harris, Chris (2010). "Fluid–Rock Interaction in the Miocene, Post-Caldera, Tejeda Intrusive Complex, Gran Canaria (Canary Islands): Insights from Mineralogy, and O- and H-Isotope Geochemistry". Journal of Petrology. 51: 2149–2176. doi:10.1093/petrology/egq052.
- ↑ Tawadros, E. Edward (2011). Geology of North Africa. Boca Raton: CRC Press. p. 79.
- ↑ Takada, A. (1987). "Structure of a cauldron in the Otoge Ring Complex, Shitara district, Aichi Prefecture, central Japan". Journal of the Geological Society of Japan. 93 (2): 107–120. doi:10.5575/geosoc.93.107.
- ↑ Johnson, S. E.; Paterson, S. R.; Tate, M. C. (1999). "Structure and emplacement history of a multiple-center, cone-sheet–bearing ring complex: The Zarza Intrusive Complex, Baja California, Mexico". Geological Society of America Bulletin. 111: 607–619. doi:10.1130/0016-7606(1999)111<0607:SAEHOA>2.3.CO;2.
- ↑ Wen, X.; Ma, C.; Mason, R.; Sang, L.; Zhao, J. (2015). "Subterranean origin of accreted lapilli in cone-sheets of the houshihushan sub-volcanic ring complex, Shanhaiguan, China". Journal of Earth Science. 26: 661–668. doi:10.1007/s12583-015-0581-4.
- ↑ Ancochea, Eumenio; Huertas, María José; Hernán, Francisco; Brändle, José Luis (2014). "A new felsic cone-sheet swarm in the Central Atlantic Islands: The cone-sheet swarm of Boa Vista (Cape Verde)". Journal of Volcanology and Geothermal Research. 274: 1–15. doi:10.1016/j.jvolgeores.2014.01.010.
- ↑ Magee C.; Stevenson C.; O'Driscoll B.; Schofield N.; McDermott K. (2012). "An alternative emplacement model for the classic Ardnamurchan cone sheet swarm, NW Scotland, involving lateral magma supply via regional dykes" (PDF). Journal of Structural Geology. 44: 73–91. doi:10.1016/j.jsg.2012.08.004.