Stages Of Intrusion Research Articles

Network Attack Scenarios Extraction and Categorization by Mining IDS Alert Streams

The past few years have witnessed significant increase in DDoS attacks on Internet, prompting network security as a great concern. With the attacks getting more sophisticated, automatically reasoning the attack scenarios in real time and cat- egorizing those scenarios become a critical challenge. However,the overwhelming flow of events generated by Intrusion Detection System (IDS) sensors make it hard for se- curity administrators to uncover hidden attack plans. This paper presents a semantic vector space model to extract and categorize attack scenarios based on First-order Log- ics (FOL) and linguistics. The modified Case Grammar is introduced to formalize the heterogeneous IDS alerts into uniform structured alert streams. The attack resolution is then used to generate attack semantic network. Afterwards, mutual information is used to determine the alert semantic context range. Based on the attack ontology and alert contexts, attack scenarios are extracted and the alerts are represented as attack semantic space vectors. Finally text categorization technique are used to categorize the intrusion stages. The preliminary results show our model has better performance than the traditional alert correlations.

Granites, dynamic magma chamber processes and pluton construction: the Aztec Wash pluton, Eldorado Mountains, Nevada, USA

ABSTRACTThe mid-Miocene Aztec Wash pluton is divisible into a relatively homogeneous portion entirely comprising granites (the G zone, or GZ), and an extremely heterogeneous zone (HZ) that includes the products of the mingling, mixing and fractional crystallisation of mafic and felsic magmas. Though far less variable than the HZ, the GZ nonetheless records a dynamic history characterised by cyclic deposition of the solidifying products of the felsic portion of a recharging, open-system magma chamber.Tilting has exposed a 5-km section through the GZ and adjacent portions of the HZ. A porphyry is interpreted as a remnant of a chilled roof zone that marks the first stage of felsic GZ intrusion. Subsequent recharging by felsic and mafic magma, reflected by repeated cycles of crystal accumulation and melt segregation in the GZ and emplacement of mafic flows in the HZ, rejuvenated and maintained the chamber. Kilometre-scale lobes of mafic HZ material were deposited as prograding tongues into the GZ during periods of increased mafic input. Thus, they are lateral equivalents of the cumulate GZ granites with which they interfinger. Conglomerate-like units comprising rounded, matrix-supported intermediate clasts in cumulate granite are located immediately above the lobes. These ‘conglomerates’ appear to represent debris flows shed from sloping upper surfaces of the lobes. Thus, the GZ can be viewed as comprising distal facies, remote from the site of mafic recharging in the HZ, and the HZ as comprising proximal facies.Elemental chemistry suggests that the GZ cumulate granites represent a second-stage accumulation from an already evolved melt, and that coarse, more mafic, feldspar+biotite+accessory mineral ± hornblende rocks trapped between mafic sheets in the HZ are the initial cumulates. Fractionated melt accumulated roofward and laterally, and was the direct parent of the ‘evolved’ GZ cumulates. The most highly fractionated, fluid-rich melts accumulated at the roof.

Rift‐zone development around a plume‐related magma centre on the Isle of Skye (Scotland): a model for stress inversions

ABSTRACT Using the example of the Isle of Skye in Scotland, we investigate the influence of pressure variations in upper‐crustal magma reservoirs on the development of rift‐type normal faulting around central volcanoes. The regional synmagmatic stress regime is of strike‐slip type in Scotland during the Lower Tertiary. During a prolonged period of overall high pressure in the Skye magma reservoir (gabbro intrusion stage), crustal extension results from the injection of basaltic dykes parallel to the trend of the far‐field maximum stress. During a subsequent period of pressure decrease in the reservoir (granites intrusion stage) normal faults trending parallel to the dykes are initiated. These faults tilt the upper‐crustal blocks along with the former dyke swarm and associated lava pile. Finite‐element modelling shows that a decrease of magma pressure in a circular cavity may lead, as in Skye, to a change from a regional strike‐slip to a local rift‐type normal stress regime.

Catastrophic erosion of Hellas basin rim on Mars induced by magmatic intrusion into volatile‐rich rocks

Malea and Hesperia Plana form large sectors of the rim of Hellas basin that display partly eroded volcanic shields and plains. These regions have topographic profiles that appear to be several hundred meters lower than those of adjacent rim sectors and lack prominent massifs of remnant basement that would be expected to stand above the lava plains. We interpret that before the volcanic edifices were constructed, these regions were denuded by an early stage of voluminous sill intrusion into friable, volatile‐rich impact breccia. Magma‐volatile interactions may have resulted in catastrophic generation of debris flows deposited into the adjacent basin, particularly if CO2 were involved. Later, lavas covered the eroded terrain; in turn, the lavas were eroded locally by volatile interactions. Across Mars, huge channel systems, erosional features in volcanic terranes, and vast layered deposits may be due to magma‐volatile interactions.

Size effect and time-dependent nanohardness of ZrO2-based ceramics

A modified setup and a method of dynamic indentation with a triangular symmetric force pulse of controllable amplitude and duration are employed for analyzing the time-dependent elastic properties of ZrO2-based ceramics in a contact time range of 20 ms–4 s. It is shown that the duration of the loading-unloading cycle considerably affects the dynamic hardness: the variation of the contact time from 20 ms to 4 s leads to a 20% change in the dynamic hardness for P max=25 mN. The variation of the hardness sensitivity m to the strain rate upon a transition from the initial stage of indenter intrusion to the next stages from m 1=1.56 to m 2=0.49 may point to the difference in the mechanisms of mass transfer of a material under an indenter at these stages.

Automatic hypocenter determination of volcano induced seismic transients based on wavefield coherence — an application to the 1998 eruption of Mt. Merapi, Indonesia

In order to monitor the seismic activity of Mt. Merapi (Indonesia) over a long period of time, we installed a permanent array of both broadband and short-period seismometers during the summer of 1997. Considering the requirements of an automatic classification and localization system for seismic monitoring and surveillance at active volcanoes, we split this network into three small-aperture arrays distributed around the volcano. We introduce here a newly developed method to determine the hypocenters in an automatic, non-linear manner using the coherence of seismic waves observed at the different arrays. To test this method, we analyze a swarm of VT-B events recorded by the network. The first step in this algorithm is based on a modified smoothed coherence transform. In the second step, we perform a semblance analysis applied to the 3D problem, evaluating the quality of the estimated relative onset-times. After more than one year of dormancy, Mt. Merapi renewed its activity at the end of June 1998. This gave us the opportunity to analyze all stages of dome growth, collapse and new intrusion of magma using the associated seismicity in a post-processing sense. This also allowed us to calibrate and test our newly developed automatic monitoring system using the more pronounced waveforms of VT-B events. By detecting and classifying different event types automatically, we are able to localize a large number of VT-B events, which occurred just before the initial eruption. We are also able to resolve some properties of the wavefield at Mt. Merapi, which are essential for further interpretations. Finally, the results show that the source region of the VT-B type seismicity just before the 1998 eruption is closely related to the region of subsequent high volcanic activity and therefore may represent a promising tool to forecast future eruptions.

Growth and steady state stages of thermohaline intrusions in the Arctic Ocean

Thermohaline intrusions are a widespread feature of the Arctic Ocean pycnocline and may be important for the lateral transport of heat, salt, and other tracers. In an attempt to understand the dynamics of the intrusions, we present an analysis of hydrographic observations of a front north of Svalbard. Following intrusions from profile to profile, we find that they slope upward toward the cold, fresh side of the front. However, their slope is less than that of the background isopycnals, so that the intrusions slope between horizontal and isopycnal surfaces in the “wedge” of baroclinic instability. Our analysis proceeds in two stages. First, to determine what might have caused the initial growth of the intrusions, we compare the observed intrusion properties with predictions of an instability theory. The results suggest that the intrusions developed as a form of double‐diffusive interleaving, with fluxes dominated by salt fingering and additional forcing by baroclinicity. Second, to investigate the observed finite amplitude interleaving, we apply a steady state model to the observations. A key result is that diffusive convection, not salt fingering, must be the dominant form of double diffusion in order to reach steady state. This fundamental change in dynamics is discussed in the context of adjustment from the growth stage to an eventual steady state.

The Palaeoproterozoic Kangerluluk gold-copper mineralization (southeast Greenland): Pb and Nd isotopic constraints on its timing and genesis

The Ketilidian Mobile Belt (KMB) in South Greenland is dominated by the Palaeoproterozoic Julianehab Batholith (1,850–1,770 Ma) and is bordered by supracrustal sequences. The batholith is composed of granite, granodiorite, tonalite, diorite and subordinate gabbro and appinite and formed in a juvenile magmatic arc. The supracrustal rocks consist of psammites, pelites and subordinate, interstratified mafic volcanic rocks. A Rapakivi granite suite (1,755–1,735 Ma) intrudes them. Gold is an important metal in the KMB and occurs in various settings and element associations. Here, emphasis is placed on the Kangerluluk Cu–Au mineralization in the eastern part of the mobile belt. It is hosted within a remnant supracrustal succession dominated by redundant pillowed basalts. Structurally, a syn-volcanic association with gold can be distinguished from one that is clearly related to crosscutting quartz veins. In between, calc-silicate formation in the volcanic rocks occurred contemporaneously with a pervasive sericitization (bleaching) of leucocratic granitoids that are intrusive into the volcanic sequence. Bulk rock and mineral (sulfide) Pb isotope data are comparable in the Pb isotope space. The data define two groups of mineralization where one group is characterized by relatively higher 207Pb/204Pb at given 206Pb/204Pb ratios than the other. Pb stepwise leaching (PbSL) dating experiments performed on garnet and epidote associated with both groups of mineralization confirm the offset in the Pb isotope data. With the geochronological information from PbSL, the results indicate: (1) the initial gold mineralization was genetically related to metalliferous fluids associated with the emplacement of late intrusive stages of the Julianehab Batholith (1,800–1,770 Ma); and (2) local remobilization of the initial mineralization (1,700–1,750) involved a Pb isotopically evolved fluid, which tentatively can be correlated with the intrusion of the Rapakivi granites in the area. Radiogenic Pb was not only found in altered host rocks but also in various sulfides, suggesting that fluids may have percolated through and/or originated from uranium-bearing graphitic schists which are abundant in the sedimentary package of the KMB. Lead isotopic results suggest that the Rapakivi granites may have supplied heat for renewed circulation of fluids within the supracrustal rock pile.

三宅島２０００年噴火に伴う火山性地震・火山性微動

The 2000 Miyakejima volcano activities started on Jun. 26 after 17 years of quiescence. The NIED Miyakejima volcano observational network, mainly equipped with seismometers and tiltmeters, successfully and continuously detected the migrations of magma. The volcanic activities consist of four stages : the dike intrusion (Stage 1 : Jun. 26-27), the subsidence of volcanic body (Stage 2 : Jun. 27-Jul. 8), tilt-steps and successive collapses of the summit crater (Stage 3 : Jul. 8-Aug. 18), and the subsidence of volcanic body and episodic eruptions (Stage 4 : Aug. 18-). This paper summarizes characteristic seismic phenomena that occurred at each stage; i.e., VT (volcanotectonic) earthquakes, LP (long-period) earthquakes, and volcanic tremor. Significant phenomena are the 50-second pulse waves associated with the tilt-steps at Stage 3. They reflect subsurface magmatic processes and their temporal and spatial variations.

Metasomatic alteration associated with regional metamorphism: an example from the Willyama Supergroup, South Australia

The Olary Domain, part of the Curnamona Province, a major Proterozoic terrane located within eastern South Australia and western New South Wales, Australia, is an excellent example of geological region that has been significantly altered by metasomatic mass-transfer processes associated with regional metamorphism. Examples of metasomatically altered rocks in the Olary Domain are ubiquitous and include garnet–epidote-rich alteration zones, clinopyroxene- and actinolite-matrix breccias, replacement ironstones and albite-rich alteration zones in quartzofeldspathic metasediments and intrusive rocks. Metasomatism is typically associated with formation of calcic, sodic and/or iron-rich alteration zones and development of oxidised mineral assemblages containing one or more of the following: quartz, albite, actinolite–hornblende, andradite-rich garnet, epidote, magnetite, hematite and aegerine-bearing clinopyroxene. Detailed study of one widespread style of metasomatic alteration, garnet–epidote-rich alteration zones in calc-silicate host rocks, provides detailed information on the timing of metasomatism, the conditions under which alteration occurred, and the nature and origin of the metasomatic fluids. Garnet–epidote-bearing zones exhibit features such as breccias, veins, fracture-controlled alteration, open space fillings and massive replacement of pre-existing calc-silicate rock consistent with formation at locally high fluid pressures and fluid/rock ratios. Metasomatism of the host calc-silicate rocks occurred at temperatures between ∼400°C and 650°C, and involved loss of Na, Mg, Rb and Fe 2+, gain of Ca, Mn, Cu and Fe 3+ and mild enrichment of Pb, Zn and U. The hydrothermal fluids responsible for the formation of garnet–epidote-rich assemblages, as well as those involved in the formation of other examples of metasomatic alteration in the Olary Domain, were hypersaline, oxidised, and chemically complex, containing Na, Ca, Fe 3+, Cl, and SO 4 2−. Sm–Nd geochronology indicates that the majority of garnet–epidote alteration occurred at 1575±26 Ma, consistent with field and petrographic observations that suggest that metasomatism occurred during the retrograde stages of a major amphibolite-grade regional metamorphic event, and prior to the latter stages of regional-scale intrusion of S-type granites at 1600±20 Ma. The fluids responsible for metasomatism within the Olary Domain are inferred to have been derived from devolatilisation of a rift-related volcano-sedimentary sequence, perhaps containing oxidised and evaporitic source rocks at deeper structural levels, during regional metamorphism, deformation and intrusion of granites. At the present structural level, there is no unequivocal evidence for the fluids to have been directly sourced from granites.

Interaction among upper crustal, lower crustal, and mantle materials in the Port Mouton pluton, Meguma Lithotectonic Zone, southwest Nova Scotia

The Port Mouton pluton is unique among the Late Devonian peraluminous granitoid bodies in the Meguma Lithotectonic Zone of southwestern Nova Scotia in its lithological heterogeneity, extensive physical and chemical interaction with the country rocks, clear evidence for mingling and mixing with mafic magmas, and highly abundant pegmatites. New U–Pb age determinations on monazite establish an intrusion age of 373 ± 1 Ma, similar to the ages of other Meguma Lithotectonic Zone granitoid plutons and mafic intrusions. Field relations, petrology, and geochemistry define three stages of intrusion of the Port Mouton pluton: (i) early stage, discontinuously exposed around the outer margin of the pluton, dominated by coarse-grained tonalite-granodiorite, and with Rb/Sr < 0.55, Eu/Eu* > 0.40, and GdN/LuN < 2; (ii) middle stage, occupying the interior of the pluton, dominated by medium-grained granodiorite-monzogranite, and with Rb/Sr > 0.55, Eu/Eu* < 0.40, and GdN/LuN > 2; and (iii) late stage, consisting of abundant minor sheets throughout the pluton, dominated by fine-grained tonalite, granodiorite, and leucogranite that are similar to rocks of the early and middle stages. The Port Mouton pluton shows a wider range of 87Sr/86Sri (0.7036-0.7154), and a wider range and generally higher εNdi (–3.72 to +2.12), than other granitoid rocks in the Meguma Lithotectonic Zone, potentially reflecting a complex, partially equilibrated, interaction among mantle, lower crust, and upper crust. Field, petrological, and chemical evidence for the involvement of mantle-derived magmas and melting of upper crust permit modelling of the Port Mouton pluton granitoid compositions by three simultaneous mixing equations. These mixing model results suggest that the early stage granitoid rocks can form from simple three-component mixing relationships when the bulk distribution coefficients between residuum and melt for Sr and Nd range from 1.05 to 1.18, or two-component mixing combined with fractionation of material like the known felsic lower crust. The middle stage granitoid rocks only yield solutions involving two-component mixing and fractionation of material unlike the known felsic lower crust. We conclude that the Late Devonian mafic magmas played a major role in the formation of granitoid magmas in the Meguma Lithotectonic Zone by supplying heat and material to cause partial fusion of the Avalon lower crust.

Application of cathodoluminescence to magmatic quartz in a tin granite - case study from the Schellerhau Granite Complex, Eastern Erzgebirge, Germany

A model of the cooling history of tin-bearing granitic magma forming the Schellerhau granites (Eastern Erzgebirge, Germany) is shown on the basis of quartz textures. Similar grain size, similar grain habit and correlatable growth textures of phenocrysts in different granite varieties give proof of a common crystallization history before the melts of the Schellerhau granite varieties were intruded. Four nucleation events occurred during crystallization in different crustal levels between about 20 and 1 km depth. The parental melt of the Schellerhau granites is interpreted to have contained<2.5 wt% H2O originally. The water content of the melt during the subvolcanic intrusion stage amounted to more than 5 wt% and characterizes highly evolved residual melts that enable the formation of tin deposits. This study contributes to a better understanding of the development and behaviour of fractionated tin-bearing granitic melts, and links quartz cathodoluminescence (CL) with microanalytical studies.

Gypsum precipitation/dissolution as an explanation of the decrease of sulphate concentration during seawater intrusion

The precipitation of gypsum during the intrusion of seawater in a coastal aquifer is shown to be a possible cause of the decrease of the sulphate concentration with respect to the conservative freshwater/seawater mixing observed in many field studies. Results of previously published laboratory column experiments and the application of a multicomponent reactive transport model show that gypsum precipitates during the first stages of seawater intrusion, causing a decrease in sulphate concentration. As the resultant front advances, the water becomes undersaturated with respect to gypsum when the content of seawater <50%. At that point, water samples exhibit a deficit of sulphate of several mmol/l, in the range of the field values reported in papers on intrusion in coastal aquifers. Thus, in addition to bacterial sulphate reduction by organic matter, gypsum precipitation is a possible explanation for the non-conservative behaviour of sulphate during seawater intrusion.

Multistage emplacement of the Mount Givens pluton, central Sierra Nevada batholith, California

The ca. 90 Ma Mount Givens pluton is one of the largest granodioritic to granitic intrusions in the Sierra Nevada batholith of California. Emplacement of the pluton occurred during a critical time in the tectonic evolution of the central Sierra Nevada magmatic arc, marked by a transition from regional contraction to dextral transcurrent shear. A model for the emplacement of the intrusion is developed based on detailed mapping of the pluton and its wall rocks and characterization of its internal structure by measurements of the anisotropy of magnetic susceptibility (AMS) at 351 stations. One of the key results of the study is documentation of a strong correlation between petrologic and structural fabrics in the pluton, and determination that these fabrics reflect internal magma chamber dynamics more than regional tectonic strain. The ∼80-km-long, 15–30-km-wide pluton crystallized from a multiphase, three-segment magma chamber marked by a bulbous northern lobe and linear central and southern segments. The pluton is interpreted to be tabular in shape with a thickness of ∼5 km. Most of the space for the pluton was created by piecemeal block downdrop of the magma chamber floor along three principal fracture sets, the most important of which were steeply dipping, northwest-trending fractures formed parallel to the structural grain of the arc, and vertical, north-trending extension fractures formed in response to a component of arc-parallel dextral shear. Some of these fractures acted as magma conduits, episodically filling the pluton as source rocks became depleted in melt. An initial, voluminous intrusive event (stage 1) quickly filled the southern chamber with granodiorite magma, but only partially filled the northern and central chambers. Stage 2 magmatism involved underplating of megacrystic granite in the northern chamber and lateral flow of a large batch of this magma from the northern to the central chamber, the latter delineated by a 20-km-long belt of megacrystic granite containing subhorizontal magnetic lineations that connects the pluton segments. Floor downdrop eventually ceased to be an effective space-making process in the northern lobe, and renewed magmatism (stage 3) led to expansion and doming of the chamber. As the northern lobe cooled, a ring fault ruptured within the viscoelastic stage 1–2 carapace, allowing ring dike intrusion (stage 4) and sinking of a central flap of consolidated material. The temporal and spatial variations in emplacement mechanisms demonstrated for the Mount Givens pluton (i.e., fracture generation, floor downdrop, underplating, inflation, ring diking) suggest that end-member models (e.g., fracture vs. diapir) are oversimplifications of the pluton assembly process.

Thermal and mechanical aspects of magma emplacement in giant dike swarms

We consider the thermal history and dynamics of magma emplacement in giant feeder dikes associated with continental flood basalts. For driving pressure gradients inferred for giant dike swarms, thicknesses of &lt;10 m would enable dikes to transport magma laterally over the distances observed in the field (up to thousands of kilometers) without suffering thermal lock‐up. Using time‐dependent numerical solutions for the thermal evolution of a dike channel under laminar and turbulent flow conditions in the presence of phase transitions, we investigate the possibility that the observed dike thicknesses (of the order of 100 m) result from thermal erosion of the country rocks during dike emplacement. This implies that the observed range of dike widths in giant dike swarms may reflect variations in the source volume and not the excess magma pressure. It is found that the total volume of intruded magma required to produce an order of magnitude increase in dike width via wall rock melting broadly agrees with the estimated volumes of individual flows in continental flood basalts. The presence of chilled margins and apparently low crustal contamination characteristics of some giant dikes may be consistent with turbulent magma flow and extensive melt back during dike emplacement. In this case, measurements of the anisotropy of magnetic susceptibility most likely indicate magma flow directions during the final stages of dike intrusion. Shear stresses generated at the dike wall when the dike starts to freeze strongly decrease with increasing dike width, which implies that thicker dikes may have less tendency to produce consistent fabric alignment. Our results suggest that if the dike was propagating downslope off a plume‐related topographic swell, the mechanism responsible for flow termination could possibly have been related to underpressurization and collapse (implosion) of the shallow magma plumbing system feeding the intrusion. Radial dikes that erupted at the periphery of the topographic uplift might have increased (rather than decreased) extensional stresses in the crust within the topographic uplift upon their solidification.

Emplacement of the Joshua Flat-Beer Creek Pluton (White Inyo Mountains, California): a story of multiple material transfer processes

Abstract The Joshua Flat-Beer Creek Pluton (JBP) in the White Inyo Mountains, California, is part of the Inyo batholith, which intruded a Neoproterozoic to Lower Cambrian metasedimentary sequence at about 180–160 Ma ago. Contact metamorphism around the JBP reached hornblende-hornfels- to lower amphibolite-facies conditions. The intrusion consists of three distinct phases. Field relations suggest an intrusion sequence Marble Canyon Diorite-Joshua Flat Monzonite-Beer Creek Granodiorite as nested diapirs. In the Marble Canyon Diorite as well as the Joshua Flat Monzonite the subsequent intrusions led to brecciation and stoping, but also to mingling and mixing between the Joshua Flat Monzonite and the Beer Creek Granodiorite. Fabrics in the contact aureole document several emplacement mechanisms such as stoping and dyking, ductile downward flow, partial melting and magma chamber expansion. The relative importance of the different emplacement mechanisms through time is as follows: the Marble Canyon Diorite probably intruded as dyke/sill, whereas stoping and dyking, ductile downward flow together with assimilation acted during the emplacement of the Joshua Flat Monzonite. Magma chamber expansion represents only the latest stage of intrusion during the emplacement of the Beer Creek Granodiorite into the already existing magma chamber of the JBP. AMS, quartz c -axis and strain measurements support the field observations.

Dike surface lineations as magma flow indicators within the sheeted dike complex of the Troodos Ophiolite, Cyprus

Mesoscopic flow lineations and anisotropy of magnetic susceptibility (AMS) have been measured for dikes within the Cretaceous‐age Troodos ophiolite with the goal of comparing the direction of initial magma flow through dike conduits immediately following crack propagation with that of flow of subsequent magma emplaced during later stages of dike growth. Dike margin indicators of flow include cusp axes and elongate vesicles found high in the ophiolite pseudostratigraphy and ridge‐and‐groove structures termed hot slickenlines found throughout the complex. A unique flow direction is determined where elongate vesicles near dike margins display imbrication with respect to the margin. Significant changes in vesicle elongation directions across dikes likely indicate either changes in magma flow direction after dike propagation or back‐flow of magma during the waning stages of intrusion. Surface lineations generally lie subparallel to the direction of flow inferred from AMS determinations on cores within 5 cm of dike margins. Surface lineations also lie subparallel to the long axis (ε1) of the orientation ellipsoid defined by long axes of groundmass plagioclase phenocrysts measured in sections from AMS cores. Correlation of surface lineations with interior indicators of flow (AMS, plagioclase trachytic texture) indicate that the surface features are good proxies for grain‐scale magma flow directions during dike propagation in Troodos dikes. Orientations of surface flow features in the dikes of the Troodos ophiolite indicate an approximately equal mix of subhorizontal to near‐vertical magma flow, contradicting the paradigm of primarily vertical flow of magma beneath continuous axial magma chambers at oceanic spreading centers. Our data are consistent with a model of magma emplacement both vertically and horizontally away from isolated magma chambers beneath axial volcanoes spaced along a ridge crest.

An electron microscope study of intrusions into alarm substance cells of the channel catfish

Thin and ultrathin sections of the epidermis of two channel catfish Ictalurus punctatus were studied in light and electron microscopes, respectively, to learn more about intrusions of entire other cell types into alarm substance cells, first noted in 1981. Several degrees of intrusion and several stages in the process of total intrusion are described: microvillus‐like projections, pseudopod‐like projections, telophase‐stage projections, total cell intrusion. In addition, several different cell types intrude: lymphocyte‐like cells, general epidermal cells, virus‐infected cells and other alarm substance cells. These findings indicate that the alarm substance cell is extraordinarily subject to invasion by other cell types. They suggest that its plasma membrane may have been modified so as to be somewhat less effective in preserving cell integrity (and thus more easily release its alarm pheromone on injury) than is the case with most other cell types or that the alarm substance acts as an attractant for other epidermal cells.

An electron microscope study of intrusions into alarm substance cells of the channel catfish

Thin and ultrathin sections of the epidermis of two channel catfish Ictalurus punctatus were studied in light and electron microscopes, respectively, to learn more about intrusions of entire other cell types into alarm substance cells, first noted in 1981. Several degrees of intrusion and several stages in the process of total intrusion are described: microvillus-like projections, pseudopod-like projections, telophase-stage projections, total cell intrusion. In addition, several different cell types intrude: lymphocyte-like cells, general epidermal cells, virus-infected cells and other alarm substance cells. These findings indicate that the alarm substance cell is extraordinarily subject to invasion by other cell types. They suggest that its plasma membrane may have been modified so as to be somewhat less effective in preserving cell integrity (and thus more easily release its alarm pheromone on injury) than is the case with most other cell types or that the alarm substance acts as an attractant for other epidermal cells.

Shoshonite‐hosted endeavour 48 porphyry copper‐gold deposit, Northparkes, central New South Wales

The Endeavour 48 copper‐gold orebody is the most recent discovery in the Northparkes Project, located in the Goonumbla district of central New South Wales. The discovery resulted from a small team conducting a systematic appraisal of high‐quality geological and geophysical datasets collected over 20 years of exploration in the Goonumbla district. A key element of the discovery was a rigorous assessment of low‐level aeromagnetic data coupled with persistence in drilling narrow, pipe‐like targets. The Endeavour 48 deposit is a shoshonite‐hosted porphyry copper‐gold deposit. Mineralisation is associated with quartz stockworks and a late‐stage magmatic derived sericitic overprint, and is closely related to at least two stages of quartz monzonite porphyry intrusion. These are genetically related to the biotite quartz monzonite stock (Endeavour 31) which forms the base of the deposit. The mineralisation is hosted by the intrusions, volcaniclastic sandstones, coarse volcaniclastic breccias and latitic (shoshonitic) lavas. The intrusive and volcanic suite are shoshonitic, based on their petrographic and geochemical characteristics. Pervasive biotite‐magnetite ± K‐feldspar alteration forms the earliest alteration phase which is overprinted by sericite, carbonate, albite, hematite, biotite, magnetite ± K‐feldspar related to the main quartz‐bornite stockwork veining. The final alteration assemblage is a strong pervasive sericite‐carbonate‐albite‐clay mineral overprint, which is associated with high‐grade disseminated copper and gold mineralisation. Endeavour 48 lies on Endeavour Linear and the mineralising porphyries, together with quartz veining, follow this trend. A low‐angle fault (Altona Fault) truncates the top of the deposit 50 m below surface.