The genesis and significance of N-MORB sub-types     

L. G. Viereck  M. F. J. Flower  J. Hertogen  H. -U. Schmincke  G. A. Jenner 《Contributions to Mineralogy and Petrology》1989,102(1):112-126

A global compositional dichotomy for N-MORB magma (N1/N2) is recognized on the basis of Na₂O, TiO₂, CaO, and Al₂O₃ contents, and their respective ratios. We have characterized the two magma sub-types by means of their trace element patterns, and attempted to explain the differences in major and trace element contents in terms of a partial melting model, using data from DSDP/IPOD Leg 82. Mass balance calculations for N-MORB glass and rock compositions indicate that differences between N1-and N2-MORB are consistent with simple differences (5%–10%) in the degree of partial melting of a plagioclase-(±spinel) lherzolite, at pressures <10 kbar, rather than their respective derivation from plagioclase- and spinel-lher-zolite sources. Based on published and calculated partition coefficients, and calculated source magmaphile trace element compositions, the calculations indicate that the overall range of N-MORB compositions may be derived by between approximately 8% and 20% partial melting of a fertile lherzolite source. Fluid dynamic and melt kinematic considerations will probably necessitate refinement of the model, but should also take account of its qualitative precepts.  相似文献   

Reflection Seismic Investigations In the Volcaniclastic Apron of Gran Canaria and Implications For Its Volcanic Evolution     

Thomas Funck  Thomas Dickmann  Roland Rihm  Sebastian Krastel  Holger Lykke-Andersen  Hans-Ulrich Schmincke 《Geophysical Journal International》1996,125(2):519-536

  相似文献   

IAVCEI: Who we are and what we do     

H-U Schmincke 《Bulletin of Volcanology》1993,55(6):457-466

IAVCEI: Who we are and what we do  相似文献   

Evolution of the Quaternary melitite-nephelinite Herchenberg volcano (East Eifel)     

Ulrich Bednarz  Hans-Ulrich Schmincke 《Bulletin of Volcanology》1990,52(6):426-444

The Quaternary Herchenberg composite tephra cone (East Eifel, FR Germany) with an original bulk volume of 1.17·10⁷ m³ (DRE of 8.2·10⁶ m³) and dimensions of ca. 900·600·90 m (length·width·height) erupted in three main stages: (a) Initial eruptions along a NW-trending, 500-m-long fissure were dominantly Vulcanian in the northwest and Strombolian in the southeast. Removal of the unstable, underlying 20-m-thick Tertiary clays resulted in major collapse and repeated lateral caving of the crater. The northwestern Lower Cone 1 (LC1) was constructed by alternating Vulcanian and Strombolian eruptions. (b) Cone-building, mainly Strombolian eruptions resulted in two major scoria cones beginning initially in the northwest (Cone 1) and terminating in the southeast (Cones 2 and 3) following a period of simultaneous activity of cones 1 and 2. Lapilli deposits are subdivided by thin phreatomagmatic marker beds rich in Tertiary clays in the early stages and Devonian clasts in the later stages. Three dikes intruded radially into the flanks of cone 1. (c) The eruption and deposition of fine-grained uppermost layers (phreatomagmatic tuffs, accretionary lapilli, and Strombolian fallout lapilli) presumably from the northwestern center (cone 1) terminated the activity of Herchenberg volcano. The Herchenberg volcano is distinguished from most Strombolian scoria cones in the Eifel by (1) small volume of agglutinates in central craters, (2) scarcity of scoria bomb breccias, (3) well-bedded tephra deposits even in the proximal facies, (4) moderate fragmentation of tephra (small proportions of both ash and coarse lapilli/bomb-size fraction), (5) abundance of dense ellipsoidal juvenile lapilli, and (6) characteristic depositional cycles in the early eruptive stages beginning with laterally emplaced, fine-grained, xenolith-rich tephra and ending with fallout scoria lapilli. Herchenberg tephra is distinguished from maar deposits by (1) paucity of xenoliths, (2) higher depositional temperatures, (3) coarser grain size and thicker bedding, (4) absence of glassy quenched clasts except in the initial stages and late phreatomagmatic marker beds, and (5) predominance of Strombolian, cone-building activity. The characteristics of Herchenberg deposits are interpreted as due to a high proportion of magmatic volatiles (dominantly CO₂) relative to low-viscosity magma during most of the eruptive activity.  相似文献   

Peralkaline felsic magmatism at the Nemrut volcano,Turkey: impact of volcanism on the evolution of Lake Van (Anatolia) IV     

Ray?MacdonaldEmail author  Mari?Sumita  Hans-Ulrich?Schmincke  Bogus?aw?Bagiński  John?C.?White  S?awomir?S.?Ilnicki 《Contributions to Mineralogy and Petrology》2015,169(4):34

Nemrut volcano, adjacent to Lake Van (Turkey), is one of the most important peralkaline silicic centres in the world, where magmatism for ~570,000 years has been dominated by peralkaline trachytes and rhyolites. Using onshore and Lake Van drill site tephra samples, we document the phenocryst and glass matrix compositions, confirming a complete spectrum from very rare mafic to dominantly silicic magmas. Magma mixing has been common and, along with the multi-lineage nature of the magmas, indicates that Nemrut has been a very open system where, nevertheless, compositionally zoned caps developed during periods of relative eruptive quiescence. Geothermometry suggests that the intermediate-silicic magmas evolved in an upper crustal magma reservoir at temperatures between 1100 and 750 °C, at fO₂ close to the FMQ buffer. The silicic magmas either were halogen poor or exsolved a halogen-rich phase prior to or during eruption. An unusual Pb-rich phase, with up to 98.78 wt% PbO, is interpreted as having exsolved from the intermediate-rhyolitic magmas.  相似文献   

Deposition of rheomorphic ignimbrite D (Mogán Formation), Gran Canaria, Canary Islands, Spain     

Gustav Kobberger  Hans-Ulrich Schmincke 《Bulletin of Volcanology》1999,60(6):465-485

 Rheomorphic ignimbrite D (13.4 Ma, Upper Mogán Formation on Gran Canaria), a multiple flow–single cooling unit, is divided into four major structural zones that differ in fabric and finite strain of deformed pyroclasts. Their structural characteristics indicate contrasting deformation mechanisms during rheomorphic flow. The zones are: (a) a basal zone (vitrophyre) with pure uniaxial flattening perpendicular to the foliation; (b) an overlying shear zone characterized by asymmetric fabrics and a significantly higher finite strain, with an ellipsoid geometry similar to stretched oblate bodies; (c) a central zone with a finite strain geometry similar to that of the underlying shear zone but without evidence of a rotational strain component; and (d) a slightly deformed to non-deformed top zone where the almost random orientation of subspherical pyroclasts suggests preservation of original, syn-depositional clast shapes. Rheomorphic flow in D is the result of syn- to post-depositional remobilization of a hot pyroclastic flow as shown by kinematic modeling based on: (a) the overall vertical structural zonation suggested by finite strain and fabric analysis; (b) the relation of shear sense to topography; (c) the interrelationship of the calculated vertical cooling progression at the base of the flow (formation of vitrophyre) and the related vertical changes in strain geometry; (d) the complex lithification history; and (e) the consequent mechanisms of deformational flow. Rheomorphic flow was caused by load pressure due to an increase in the vertical accumulation of pyroclastic material on a slope of generally 6–8°. We suggest that every level of newly deposited pyroclastic flow material of D first passed through a welding process that was dominated by compaction (pure flattening) before rheomorphic deformation started. Received: 25 June 1997 / Accepted: 28 October 1998  相似文献   

IAVCEI News     

H. -U. Schmincke 《Bulletin of Volcanology》1988,50(6):419-420

  相似文献   

IAVCEI news     

H -U Schmincke 《Bulletin of Volcanology》1990,53(1):72-72

  相似文献   

Arc volcanism: Edited by S. Aramaki and I. Kushiro,Elsevier, 1983, 634p., US$97.75, Dfl. 230.00     

H.-U. Schmincke 《Geochimica et cosmochimica acta》1984,48(11):2398

  相似文献   

Models for the origin of accretionary lapilli   总被引：1，自引：0，他引：1  

R. Schumacher  H. -U. Schmincke 《Bulletin of Volcanology》1995,56(8):626-639

Binding between initially cohesionless ash particles to form concentric accretionary lapilli is provided primarily by the capillary forces of liquid bridges from condensed moisture and by electrostatic attraction. Capillary forces are strong bonds if the particles are in close contact, but they decrease rapidly with increasing particle spacing. Electrostatic attraction between charged ash particles is much weaker but effective over larger distances, increasing the frequency of collision between them.Experimental results of liquid film binding of volcanic ash showed that agglomeration was most successful between 15 and 25 wt.%, defining the agglomeration window for the formation of accretionary lapilli. Below 5–10 wt.% and above about 25–30 wt.% of water, concentric agglomeration was inhibited. Particles <350 m could be selected from a wider particle population in the experiments using only small amounts of water, which can explain the growth of accretionary lapilli in pyroclastic surges around agglomeration nuclei. Experiments testing the behavior of volcanic ash in electric fields showed that ash clusters formed instantaneously when the ash entered the field between a corona discharge gun and a grounded metal plate. The maximum grain size incorporated into the artificial clusters was about 180 m but >90 wt.% of ash was <45 m.Accretionary lapilli form in turbulent ash clouds when particles carrying liquid films of condensed moisture collide with each other and when the binding forces exceed the grain dispersive forces. Larger particles >500 m act as agglomeration nuclei in surges, accreting ash <350 m around them. In pyroclastic flows the aggregates are thought to originate from already size-sorted ash at the interface between the lower avalanche part of the flow and its overriding elutriation cloud. The fine-grained rims around accretionary lapilli found close to source are interpreted to be accreted dominantly by electrostatic attraction of very fine ash similar to clustering in elutriation clouds.  相似文献