Titan-aegirine from early Tertiary ash layers in northern Denmark

Microprobe analyses on a xenocrystic suite of salites, aegirine-augites, aegirines, titan-aegirines and acmites from a lower Tertiary ash layer in northern Denmark are presented. The sodic pyroxenes show an unusual titan-enrichment and up to 42 mol.% of the component $\text{NaTi}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^{\mathrm{4+}}\text{M}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^{\mathrm{2+}}\text{Si}{}_3\text{O}{}_6\text{(}\text{M = Fe}{}^{\mathrm{2+}}\text{,}\text{Mn or Mg}\text{)}$, is estimated. Optical absorption measurements show no evidence for Ti³⁺. The titan-aegirines were formed during late to post-magmatic crystallization in a system with a high Ti⁴⁺/Fe²⁺ ratio and were followed by acmite showing enrichment in jadeite. Comparison with experimentally investigated titan-aegirine indicates crystallization far below the Mn₂O₃Mn₃O₄f₀₂ buffer.     

A shale buchite xenolith with Al-armalcolite and native iron in a lava from Asuk,Disko, central West Greenland

A native iron bearing buchite xenolith enclosed in basalt in a native iron bearing lava from Disko is similar in chemistry, apart from volatile components, to unheated Mesozoic to early Tertiary carbonaceous shale sediments from West Greenland, believed to have been the major contaminant and reducing agent causing the formation of the native iron in the volcanic rocks on Disko. The shale buchite has preserved original sedimentary lamination and experienced only a comparatively short-lived heating which allowed only short-range equilibration. The xenolith contains native iron and graphite, while the immediately enclosing basalt does not, and demonstrates the indigenous reducing properties of the shales when heated to high (1,150–1,200 ° C) temperatures at low pressures. Sedimentary clastic iron titanium oxide grains have reacted with the immediately surrounding matrix and completely recrystallized to aggregates of rutile and Al-armalcolite with up to 24 mol% Al₂TiO₅. The Al-armalcolites contain 5 to 11 mol% of the anosovite (Ti₃O₅) component. They show a considerable variation in iron-magnesium ratio due to small-scale variations in bulk chemistry to varying f _O2 and to the effects of progressive melting of the sediment. Glassy veins in the buchite, formed along original fractures in the sediment, contain an assemblage of cordierite, low Ca-pyroxene, plagioclase, ilmenite, ferropseudobrookite-rich armalcolite, iron metal, troilite and acid glass, and crystallized under higher oxygen fugacities than the buchite interior, probably due to influx from the less reduced enclosing basalt magma.     

The Lyngen Gabbro: the lower crust of an Ordovician Incipient Arc

We present evidence for the origin of the Lyngen Gabbro of the Ordovician Lyngen Magmatic Complex in Troms, Northern Norway. The two magmatic suites of the Lyngen Gabbro strike parallel NNE-SSW, and have distinct magmatic signatures. We define these signatures by using major and trace-element analyses together with selected major- and trace-element mineral analyses and ¹⁴³Nd/¹⁴⁴Nd-isotope whole-rock analyses of gabbroic to tonalitic plutonic rocks from seven detailed cross-sections from this large gabbro-complex. The Western suite of the Lyngen Gabbro precipitated from magma that may have been derived from the same system as the associated volcanic rocks. The gabbros have high An-content (An_>90) of their plagioclases relative to co-existing mafic minerals. Together with somewhat high _Nd(t) values (+6), this implies that the parental magmas were hydrous tholeiites similar to those found in back arc basins today. The Eastern suite, on the other hand, consist of cumulates that were precipitated from melts resembling those of ultra-depleted high-Ca boninitic magmas found in fore-arcs. Extremely high-An plagioclases (An_>95) co-exist with evolved mafic minerals and oxides, and the _Nd(t) values are lower (+4) than in the Western suite. The Eastern suite has no volcanic counterpart, but dikes intersecting the suites have compositions that possibly represent its parental magma. The oceanic Rypdalen Shear Zone generally separates the two suites in the north, but several non-tectonic transitions from boninitic to tholeiitic signatures southwards advocate that the magmatism happened concurrently. The magmatic proximity between the suites, the hydrous magmatism and the absence of a silicic or calc-alkaline mature arc section, suggests that the Lyngen Gabbro formed in the Iapetus Ocean under conditions presently found in incipient arcs later emplaced as outer arc highs.     

Acidic compounds in biodegraded petroleum

Twelve oil samples have been characterised by titration, FT-IR and chromatographic analysis to determine the differences between the organic acid composition of biodegraded and non-biodegraded oils. The biodegraded oils have higher total acid and total base contents, both by titration and extraction. The molecular weight ranges of the extracted acids are lowest in the biodegraded oils, and the equivalent weight calculations indicate a dominance of multi-functional molecules. Gel permeation chromatography gives a molecular weight range with most of the molecules between 300 and 500 g/mol. FT-IR shows that the extracted acids from biodegraded oils are more carboxylic and aliphatic while the non-degraded oils are more phenolic. Molecular analysis of the derivatised extracts give UCM envelopes for biodegraded oils, and no molecular identification. The results indicate that the acidic constituents in biodegraded oils are a product of the biodegradation, as the composition is very different from the non-biodegraded oils.     

Direct Sensor Orientation for Large Scale Mapping—Potential, Problems, Solutions

Georeferencing is one of the most important tasks in photogrammetry. Traditionally it has been achieved indirectly using the well-known method of aerial triangulation. With the availability of integrated GPS and inertial measurement units (IMU), this situation changed. Direct determination of exterior orientation is now possible. Today, direct and integrated sensor orientation is used for a wide range of sensors including lidar and SAR, as well as for digital line scanner systems and aerial cameras. This paper investigates the performance of direct and integrated sensor orientation for large scale mapping using the data-set of the 'Integrated Sensor Orientation' test of the European Organisation for Experimental Photogrammetric Research (OEEPE—now known as EuroSDR). The concept, potential, problems and solutions of direct and integrated sensor orientation are discussed.     

Lithospheric structure of the Tornquist Zone resolved by nonlinear P and S teleseismic tomography along the TOR array

The main aim of the TOR project is to study the lithospheric–asthenospheric boundary structure under the Sorgenfrei–Tornquist Zone, across northern Germany, Denmark and southern Sweden. Relative arrival-time residuals of teleseismic P and S phases from 51 earthquakes, recorded by 150 seismic stations along the TOR array, were used to delineate the transition zone in the studied area. The effects of crustal structures were investigated by correcting the teleseismic residuals for travel-time variations in the crust based on a 3D crustal model derived from other data. The inversion was carried out for S phases. The results were then compared with the corresponding P-wave models. As expected, the derived models show that the relatively old and cold Baltic Shield has higher velocity at depth than the younger lithosphere farther South. The models show two sharp and distinct increases in depth to velocities which are low compared to our reference model, as we move from South to North. The location and sharpness of these boundaries suggests that the features resolved are, at least partially, compositional in origin, presumably related to mantle depletion. A sharp and steep subcrustal boundary is found roughly coincident with the southern edge of Sweden. This is below where the edge of the Baltic Shield is usually placed, based on surface geological evidence (the Sorgenfrei–Tornquist Zone). Another less significant transition is recognised more or less beneath the Elbe-lineament. Relatively high d(V_p / V_s) ratios under the central part of the profile (Denmark) indicate relatively low S-velocity in an area where a gravity high supports the hypothesis of extensive mafic intrusions.     

Stratigraphy of the Middle Devonian boundary: Formal definition of the susceptibility magnetostratotype in Germany with comparisons to sections in the Czech Republic, Morocco and Spain

One major difficulty in geology is high-resolution correlation among widely separated sections, especially in the Paleozoic where magnetostratigraphy polarity is not well established because rocks are often remagnetized, where critical biostratigraphic zonation may be poor or lacking, or where structural complexities make correlations very difficult. To address this problem, we have been using magnetostratigraphy susceptibility measurements. Here, we report our work from the Middle Devonian in Europe and North Africa. The Middle Devonian (Emsian–Eifelian) global boundary stratotype section and point (GSSP), located in the Eifel Hills, western Germany, was ratified by the International Subcommission on Stratigraphy in 1985, after careful evaluation of the biostratigraphy for this and many other sections. The boundary interval has been characterized using biostratigraphy, and the beginning of the Eifelian stage has been specifically defined by the first occurrence of the conodont Polygnathus costatus partitus. We have collected the Eifel Hills section for magnetic susceptibility (MS) measurement and here we establish it as the magnetostratotype for the Emsian–Eifelian stage boundary, by formally defining the magnetostratigraphy susceptibility for the section. We then collected, measured and compared the magnetostratotype to four other sections for which conodont biostratigraphy has been studied and where P. costatus partitus is present; two Emsian–Eifelian sections in Morocco and two sections in the Czech Republic (including the Emsian–Eifelian parastratotype). Finally, we have measured the MS for the El Puerto Creek section in the Cantabrian Mountains of Spain and identified the location of the Emsian–Eifelian boundary within the section based on MS comparison to the GSSP in conjunction with excellent biostratigraphic indicators, primarily brachiopods. While the conodont zonation in the El Puerto Creek section is poorly defined, we believe that the correspondence between the MS and biostratigraphy in the section allows the identification of the Emsian–Eifelian boundary. These results indicate that this method can be successfully applied to marine sequences where ambiguities in correlation exist.     

Temporal development of the 1999 intrusive episode in the Eyjafjallajökull volcano, Iceland, derived from InSAR images

Eyjafjallajökull volcano, located in southern Iceland, is characterized by its quiet nature. Only about a handful of earthquakes associated with the volcanic system had been detected prior to the 1990s. Earthquake swarms did, however, occur in 1994 and 1999. Here we investigate the spatio-temporal evolution of a magmatic intrusion associated with the 1999 earthquake swarm via analysis of produced surface deformation. A series of interferometric synthetic aperture radar (InSAR) images, spanning various periods of the intrusion, show that in 1999 surface deformation occurred mainly on the southern flanks of the volcano. The deformation amounts to more than 20 cm of range change. Inverse modeling resolves the deformation source to be a sill intrusion at 6.3 km depth. Sill opening was up to 1 m and the total intruded volume amounts to ～0.03 km³. The InSAR data display a migration of the center of deformation through time, enabling us to create time-dependant sill-opening models. Furthermore, we investigate the spatio-temporal distribution of earthquakes and find that the distribution supports the InSAR derived model and additionally provides indications for a possible site of a feeder channel. Magmatic flow-rate estimates indicate an initial intrusion rate of 4–6 m³/s, declining over a few weeks.     

震后地形变与孔隙压力瞬态变化的相互关系

大震改变地壳的应力,从而触发地震及其余震。一系列随时间变化的过程,包括余滑、孔隙流体的流动、下地壳和上地幔粘性的张驰、断层附近应力和孔隙压力调整以及地震的触发进程。然而,尽管进行过多次尝试,但通过直接场地的观测,很难将这些过程区分开来。这里我们采用一种星载雷达干涉图和冰岛南部地震带两个6.5级地震地热井水位变化过程结合的测量法。干涉图记录到的形变既不能用余滑也不能用粘-弹性张驰来解释,但它与地震发生后最初两个月孔隙弹性物质的回跳一致,这可以用地震引起水位变化的快速恢复(1—2个月)来证实,相反余震序列的持续时间达到3.5年,这表明余震的持续时间并不是由孔隙流体的流动控制的,但是,因为表面应变是由地壳浅部孔隙压力的变化控制的,因此,我们不能排除在余震发生深度存在较长时间的孔隙压力瞬态变化。余震的持续时间与随速度和状态变化的摩擦定律控制的地震活动变化速率模型是一致的。