| Abstract: | Photographs obtained by the ANGUS survey system at 21??N reveal many similarities to the geological processes delineated at other spreading centers and in particular those observed in the Galapagos Rift at 86??W. The region of recent volcanism is restricted to a narrow zone (Zone 1) approximately 1 km wide. This suggests that the width of the magma chamber feeding these flows is also narrow at the top. Variations in sediment cover are used to subdivide the flows within Zone 1 into three sheet-flow/pillow-flow pairs. The youngest pair appears to have erupted form a linear fissure 8 km long running parallel to the valley axis. This fissure is part of a larger en echelon pattern of eruptive fissures. Active hydrothermal vents associated with the youngest flows are situated directly above the apparent eruptive fissure. The high (350??C) temperature for some of the fluids exiting from the vents suggests a highly restricted circulation system involving, at times, little to no mixing with cold seawater. The lava terrain in the remainder of Zone 1 and bordering regions is characterized by extensive fracturing, further suggesting a narrow upper dimension to the magma chamber and also that subsurface hydrothermal deposition of massive sulfides may lead to a reduction in the mixing processes. ?? 1981. |
| Genre: | Article |
| ProdID: | 70011921 |
| Citation Author: | Ballard, R. D.; Francheteau, J.; Juteau, T.; Rangan, C.; Normark, W. |
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| Citation End Page: | 10 |
| Citation Issue: | 1 |
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| Citation Language: | English |
| Citation Larger Work Title: | Earth and Planetary Science Letters |
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| Citation Number Of Pages: | 10 |
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| Citation Search Results Text: | East Pacific rise at 21??N: The volcanic, tectonic, and hydrothermal processes of the central axis; 1981; Article; Journal; Earth and Planetary Science Letters; Ballard, R. D.; Francheteau, J.; Juteau, T.; Rangan, C.; Normark, W. |
| Citation Start Page: | 1 |
| Citation Volume: | 55 |
| Citation Year: | 1981 |
| Type: | citation/reference |
| Text: | East Pacific rise at 21??N: The volcanic, tectonic, and hydrothermal processes of the central axis; 1981; Article; Journal; Earth and Planetary Science Letters; Ballard, R. D.; Francheteau, J.; Juteau, T.; Rangan, C.; Normark, W. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Thu, 1 Jan 1981 00:00 -0600 |
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