Pillow lavas and fluvio-lacustrine deposits in the northeast of Paraná Continental Magmatic Province, Brazil
18
Citation
51
Reference
10
Related Paper
Citation Trend
Keywords:
Pillow lava
Alluvial fan
Lava field
Lithostratigraphy
The Xujiatun gigantic pillow lava in Yixian County of Western Liaoning occurs in the sedimentary interbed of volcanic rocks, which belong to the second subcycle of Yixian cycle. The gigantic pillow lava, characterized by huge pillow bodies (5 to 8 m) and diverse shapes,constitutes a distinctive landscape of volcanic rocks. Each pillow body is generally composed of three parts, i.e. chilled border, transitional belt and core, which distinguish each other in their colors, quantity and size of vesicles and amygdales. Belonging to basaltic andesite, the pillow lava could be petrologically and geochemically compared with the underlying volcanic rocks. The pillow lava was formed as a result of condensation of magma in lake, when it effused again during the intermittent of volcanic activity in the second subcycle. It belongs to continental volcanic rock,which is obviously different from marine basaltic pillow lava.
Pillow lava
Lava field
Cite
Citations (0)
Pillow lava may be the most abundant type of lava morphology on Earth throughout most of Earth’s history. Pillow presence always implies eruption/emplacement of lava into (1) a medium with a significantly different viscosity than that of the lava, and (2) a medium in which heat can be removed efficiently enough from the lava/medium interface to prevent whole scale physical and chemical homogenization. Although the ‘medium’ is most commonly water, pillow-shaped lava can also form by intrusion into wet sediment or even emplacement into cooler, higher viscosity magma. During glaciovolcanic eruptions, pillow lava forms in a variety of different environments including (1) eruptions into water at variable confining pressures (e.g. pillow ridges/mounds), (2) intrusion into unconsolidated volcaniclastic materials (e.g. pepperite and pillowed dike margins), (3) eruption into water-filled, ice-confined tunnels, and (4) flow of subaerial lava into englacial lakes (e.g. pillow lava deltas).
Pillow lava
Lava dome
Subaerial
Effusive eruption
Lava field
Cite
Citations (0)
Ash Mountain, South Tuya, and Tuya Butte are three small basaltic volcanoes in the Stikine volcanic belt of northern British Columbia. The volcanoes rise 700, 500, and 400 m above their bases and are about 3.2, 1.6, and 2.6 km 3 in volume, respectively. They began eruptive activity under several hundred meters of overlying glacial ice, or water in an ice‐impounded lake, and undegassed pillow lava was erupted and forms the bases of all three. Later, as the vents grew into shallow water, explosive phreatomagmatic activity erupted partly degassed glassy tuffs. Finally, when the volcano emerged through the surface of the ice or water (or the water was drained), degassed subaerial lava flows were erupted and were converted to assemblages of foreset‐bedded pillow breccia and pillow lava when subaerial flows crossed a shoreline and flowed into meltwater lakes. The undegassed subglacial pillow base of Ash Mountain is overlain by partly degassed pillows and hyaloclastite tuff cut by dikes; at South Tuya the pillow base is overlain by hyaloclastite tuffs and lenses of pillow lava; at Tuya Butte the pillow base is overlain by foreset‐bedded pillow lava, pillow breccias, and hyaloclastite tuffs, which in turn are overlain by subaerial lava flows composing a small shield volcano. The undegassed basal subglacial pillow lava of the three volcanoes contain 0.10 ± 0.01 wt % sulfur and ∼0.5 wt % H 2 O. The overlying partly degassed assemblages contain 0.06 ± 0.02% sulfur and ∼0.2% H 2 O at Ash Mountain, 0.07±0.01% sulfur at South Tuya, and 0.03±0.01% sulfur at Tuya Butte. The differences in the degree of degassing can be related to the nature of eruption and quenching and the distance of flow of the subaerial lava. When the volcanoes switched from subglacial to shallow water or subaerial eruptions, as shown by change to more explosive activity and then to subaerial lava flows (and by a marked reduction of sulfur in volcanic glass), the magma shifted from tholeiitic to alkalic composition. This transition occurs at each of the three volcanoes. The tholeiitic and alkalic magmas cannot be related by shallow crystal fractionation and apparently originated by differing degrees of deep melting at a mantle source. Prior to eruption the tholeiitic melts overlay alkalic melts in shallow chambers underlying each of the volcanoes because of their lower density and were, therefore, the first to erupt under subglacial conditions. As the volcano grew through the ice (or ice‐impounded water), the volcanic conduit vented to the atmosphere, producing a partial depressurization of the conduit and the subsurface chamber. This sudden reduction in confining pressure caused enhanced vesiculation of volatile saturated melts, particularly of the more volatile‐rich alkalic melts, causing them to rise to the top of the chamber and erupt.
Pillow lava
Subaerial
Breccia
Lava field
Cite
Citations (37)
Axial Seamount, an active submarine volcano on the Juan de Fuca Ridge at 46°N, 130°W, erupted in January 1998 along 11 km of its upper south rift zone. We use ship‐based multibeam sonar, high‐resolution (1 m) bathymetry, sidescan sonar imagery, and submersible dive observations to map four separate 1998 lava flows that were fed from 11 eruptive fissures. These new mapping results give an eruption volume of 31 × 10 6 m 3 , 70% of which was in the northern‐most flow, 23% in the southern‐most flow, and 7% in two smaller flows in between. We introduce the concept of map‐scale submarine lava flow morphology (observed at a scale of hundreds of meters, as revealed by the high‐resolution bathymetry), and an interpretive model in which two map‐scale morphologies are produced by high effusion‐rate eruptions: “inflated lobate flows” are formed near eruptive vents, and where they drain downslope more than 0.5–1.0 km, they transition to “inflated pillow flows.” These two morphologies are observed on the 1998 lava flows at Axial. A third map‐scale flow morphology that was not produced during this eruption, “pillow mounds,” is formed by low effusion‐rate eruptions in which pillow lava piles up directly over the eruptive vents. Axial Seamount erupted again in April 2011 and there are remarkable similarities between the 1998 and 2011 eruptions, particularly the locations of eruptive vents and lava flow morphologies. Because the 2011 eruption reused most of the same eruptive fissures, 58% of the area of the 1998 lava flows is now covered by 2011 lava.
Seamount
Lava field
Pillow lava
Effusive eruption
Lava dome
Submarine volcano
Seafloor Spreading
Cite
Citations (78)
Pillow lava
Seafloor Spreading
Rift zone
Lava field
Cite
Citations (43)
Pillow lava
Lava field
Subaerial
Volcanic plateau
Silicic
Stratovolcano
Shield volcano
Volcanic cone
Effusive eruption
Rift zone
Cite
Citations (13)
Lava field
Pillow lava
Lava dome
Subaerial
Scoria
Meltwater
Effusive eruption
Cite
Citations (13)
Abstract We present geological observations and geochemical data for the youngest volcanic features on the slow spreading Mid‐Atlantic Ridge at 8°48′S that shows seismic evidence for a thickened crust and excess magma formation. Young lava flows with high sonar reflectivity cover about 14 km 2 in the axial rift and were probably erupted from two axial volcanic ridges each of about 3 km in length. Three different lava units occur along an about 11 km long portion of the ridge, and lavas from the northern axial volcanic ridge differ from those of the southern axial volcanic ridge and surrounding lava flows. Basalts from the axial rift flanks and from a pillow mound within the young flows are more incompatible element depleted than those from the young volcanic field. Lavas from this volcanic area have 226 Ra‐ 230 Th disequilibria model ages of 1000 and 4000 years whereas the older lavas from the rift flank and the pillow mound, but also some of the lava field, are older than 8000 years. Glasses from the northern and southern ends of the southern lava unit indicate up to 100°C cooler magma temperatures than in the center and increased assimilation of hydrothermally altered material. The compositional heterogeneity on a scale of 3 km suggests small magma batches rising vertically from the mantle to the surface without significant lateral flow and mixing. The observations on the 8°48′S lava field support the model of low‐frequency eruptions from single ascending magma batches that has been developed for slow spreading ridges.
Lava field
Pillow lava
Magma chamber
Rift zone
Shield volcano
Lava dome
Cite
Citations (6)
Pillow lava
Breccia
Shield volcano
Lava field
Magma chamber
Flood basalt
Cite
Citations (23)
Pillow lava
Lava field
Lava dome
Felsic
Cite
Citations (62)