Neshveh intrusion which is located in the NW of Saveh City is a part of Sahand-Bazman magmatic arc within the Central Iranian zone. This intrusion consists of quartz-monzogabbro, quartz-mon- zodiorite, granodiorite and granite that have intruded into the Eocene volcano-sedimentary rocks. This intrusion is medium to high-K calc alkaline, metaluminous, and I-type granitoid. All phases of the Neshveh granitoid are characterized by LREE-rich patterns with high LREE/HREE ratio and negative Eu anomalies. Similarity of patterns suggests a comagmatic source for these rocks and demonstrates the role of magmaticdifferentiation in their evolution. Clinopyroxene classified as calcic type with varying from clinoenstatite-clinofferosillite to diopside and augite from quartz- monzogabbros to quartz-monzodiorite and granodiorite. Plagioclase composition varies from by- townite and labradorite in quartz-monzogabbros to andesine in quartz-monzodiorites and oligoc- lase in granodiorites and granites. Core of some plagioclases in granodiorites and granites shows the calcic composition which is labradorite and andesine in granodiorite and andesine in granites. Field investigations along with petrographic and geochemical studies indicate that all phases of the Neshveh intrusion derived from a common magma source as a result of mineral differentiation. Geochemical evidences show smooth differentiation trends in which most of major elements (ex- cept Al 2 O 3 , K 2 O and Na 2 O) are negatively correlated with SiO 2 and K 2 O, Ba, Rb, Ce, Nb, and Zr are
been inferred to have a bulk solid/liquid distribution coeﬃ- cient (D) similar to that of the light to middle rare earth ele- ments, Ce, Nd, and Pr, based on the constancy of the Mo/Ce, Mo/Nd, Mo/Pr ratios observed in various terres- trial samples (Sims et al., 1990; Newsom and Palme, 1984; Newsom et al., 1986). Hekla lavas show that although statis- tically indistinguishable, the Ce/Mo ratio decreases system- atically from 50 to 36 from basalts to rhyolites, indicating that Mo is slightly more incompatible than Ce during mag- matic diﬀerentiation (Fig. 3a). Both elements remain incom- patible (bulk D < 1) throughout the sequence however. In contrast to the relative incompatibility expected for mantle melting (Sun and McDonough, 1989), Mo is more incom- patible than Nb and Ta during magmatic diﬀerentiation at Hekla (Fig. 3c and d), with a decrease from 29 to 17 for Nb/Mo and 1.7 to 0.4 for Ta/Mo. This presumably reﬂects the removal of accessory phases that fractionate high ﬁeld strength elements (HFSE). Rubidium is more incompatible than Mo, the Rb/Mo nearly doubling from 8 to 14 from basalt to rhyolite (Fig. 3e). The K/Rb displays a concomi- tant decrease from 430 to 350. As a result, the K/Mo ratio increases only slightly from 4; 000 to 5; 000 (Fig. 3f). Therefore, the bulk D for Mo these in magmas must lie between that of K and that of Ce. This is conﬁrmed by inspection of the La/Mo ratio, which is relatively uniform in Hekla lavas (Fig. 3b). There seems to be a hint of diﬀer- ences in La/Mo and Ce/Mo ratios between basalt and dacite (Fig. 3a and b), and the ratios of andesite fall in between them, which could be an indication of mixing eﬀect. This concurs with the proposed three-stages model for Hekla magmas (Sigmarsson et al., 1992). The diﬀerence between basalt and dacite in La/Mo or Ce/Mo may have resulted from processes related to partial melting. While this is con- sistent with the three-stage model, it should be noted that the eﬀect is small; the LREE/Mo ratios for all Hekla lavas are very similar.
1992; Chekol et al., 2011). Diﬀering models of magmatic evolution for Hekla have been proposed. Sigmarsson et al. (1992) suggested a multi-stage model whereby basaltic melt pools towards the bottom of a shallow crustal magma chamber undergoes fractional crystallisation and evolve along a line of liquid descent to basaltic andesite. This melt triggers melting of crustal lithologies to form a magma of dacitic composition, which in turn mixes with the basaltic andesite magma to form a melt of andesitic composition. This hybrid melt progresses along a line of liquid descent to generate the rhyolites. This model has been recently chal- lenged based on coupled radiogenic isotope data and geo- physical observations, that the diﬀerentiation of the basaltic parent melt to intermediate compositions of basaltic-andesites could be accounted for by simple closed system fractional crystallisation (Chekol et al., 2011). This model diﬀers from that of Sigmarsson et al. (1992) in that it suggests that these early basic to intermediate melts were generated within a deep seated magma chamber, this in turn supplied magma to a series shallower, crustal melt lenses which underwent a process of assimilation fractional crystallisation (e.g. DePaolo, 1981). Despite these two dif- fering models no fundamental diﬀerence exists with respect to the application of the Hekla suite to examine the mag- matic behaviour of Zr isotopes owing to the nature of the potential crustal assimilant.
Keywords: Thallium, stable isotopes, Hekla, Anatahan, magmaticdifferentiation
Geochemical research has unequivocally demonstrated through major, trace and long-lived radiogenic isotopes that intraplate and subduction-related volcanism taps a chemically heterogeneous mantle (e.g., Arculus and Powell 1986; Ellam and Hawkesworth, 1988; Hofmann, 1997; Hofmann and White, 1982; Jackson and Dasgupta, 2008; Stracke et al. 2005; White, 2015; Weaver, 1991; Zindler and Hart, 1986). For example, the addition of sediment, sediment melts, metasomatically enriched mantle, recycled oceanic crust and fluids derived thereof have all been invoked to explain chemical heterogeneity in basaltic lavas. Radiogenic Sr-Nd-Pb-Hf isotopes illustrate clear differences in mantle sources on a global scale. The inherent difficulty in interpretation of radiogenic signatures is that they can be explained by different evolutionary, time-dependent paths, simply by choosing variable source component(s) and elemental partition coefficients. ‘Canonical’ trace element ratios are also often used to ‘see-through’ magmatic processes and examine the inaccessible mantle source, the assumption being that the partitioning of the two ratioed elements is identical in the given phase assemblage. However, the use of trace element ratios to infer mantle sources requires primitive basalts, since crystal fractionation of trace element rich accessory phases (e.g., zircon and apatite) significantly affects many ‘canonical’ ratios. Thus lively debate persists, with starkly contrasting interpretations possible using the same geochemical signatures of primitive basalts (e.g., Samoa: Workmann et al., 2004 versus Jackson et al., 2007).
mid-ocean ridge basalts compared to the sub-arc mantle, regions central to the mediation of crust-mantle mass balances. Here we present the first stable vanadium isotope measure- ments of arc lavas, complemented by non-arc lavas and two co-genetic suites of fraction- ating magmas, to explore the potential of V isotopes as a redox proxy. Vanadium isotopic compositions of arc and non-arc magmas with similar MgO overlap with one another. However, V isotopes display strikingly large, systematic variations of ~2 ‰ during magmaticdifferentiation in both arc and non-arc settings. Calculated bulk V Rayleigh fractionation factors (1000 lna min-melt of -0.4 to -0.5 ‰) are similar regardless of the oxidation state of the
In contrast to the MORB dataset, Ce/Tl does not remain constant through magmaticdifferentiation at Hekla, and instead displays a steady decrease, consistent with Tl remaining incompatible whilst Ce is incorporated into fractionating clinopyroxene (Fig. 6b). Intriguingly, Anatahan, Ce/Tl is 335 ± 178 2sd, which is lower than the entire MORB dataset (Ce/Tl = 1280 ± 430 2sd), and instead overlaps with the Tonga back arc basin (221 ± 103 2sd; Jenner et al., 2015) and lavas from the Aleutian arc (426 ± 523 2sd; Nielsen et al., 2016a). The depressed and constant Ce/Tl in subduction-related settings could be a potential indicator of prior melt depletion of the mantle wedge. Future examination of other subduction zones will determine how sensitive Tl and Ce/Tl ratios are to the competing effects of wedge depletion and sediment addition.
the solubility varies significantly in different magmatic systems. In general, water solubility in felsic magmas such as those of rhyolite and andesite composition is significantly greater than the solubility in basalt melts (Hamilton et al. 1964; Dixon and Stolper 1995; Behrens and Jantos 2001; Zhang 1999). This would be expected because of the higher alkali/alkaline earth and Si/Al ra- tios in rhyolite and andesite melt compared with melts of basaltic composition. These solubility relationships have been modeled with a variety of empirical models (e.g., Spera 1974; Burnham 1975; Dixon and Stolper 1995; Behrens and Jantos 2001). However, quantitative linkage between solubility behavior in chemically simple melts and more complex natural magma compositions await detailed structural characterization of the water solution mechanisms in simple and complex magmatic melts.
A tsunami occurs when a large body of water is suddenly displaced from its equilibrium position, generating long waves which propagate with a low energy loss from deep to shallow waters, where they rapidly decrease in velocity and reach high amplitudes in coastal areas. Volcano- related tsunamis can be associated with a variety of vol- canic activities, such as submarine explosions in shallow waters, dense pyroclastic flows entering in the water and submarine mass movements. Within the context of the present study, these volcanic activities are often associated with magmatic unrest. Non-magmatic unrest phenomena are often slow and continuous, suggesting that non- magmatic unrest manifestations (apart from phreatomag- matic and phreatic eruptions) are not advantageous for tsunami triggering, however, tsunamis can also be gener- ated as a secondary effect of non-magmatic outcomes (e.g., mass failures and PDC). In general, tsunamis due to vol- canic activity remain a poorly investigated field, with only a few recent studies (e.g., Maeno and Imamura 2007, 2011; Paris et al. 2014).
Magmatic phenomena such as volcanic eruptions on the earth’s surface show, among others, that melt is able to as- cend from partially molten regions in the earth’s mantle. The melt initially segregates through the partially molten source region and then ascends through the unmolten lithosphere until it eventually reaches the surface. Within supersolidus source regions at low melt fractions, melt is assumed to slowly percolate by two-phase porous flow within a deform- ing matrix (McKenzie, 1984; Schmeling, 2000; Bercovici et al., 2001), followed by melt accumulation within rising high-porosity waves (Scott and Stevenson, 1984; Spiegel- man, 1993; Wiggins and Spiegelman, 1995; Richard et al., 2012) or focusing into channels which can possibly penetrate into subsolidus regions. Stevenson (1989) carried out a linear stability analysis and found conditions at which flow insta- bilities may arise, which may result in different 3-D shapes like elongated pockets, channels or porosity waves (Richard- son, 1998; Wiggins and Spiegelman, 1995). Formation of 3- D channels within a deforming matrix has been demonstrated in Omlin et al. (2018) or Räss et al. (2014). Here we focus on the supersolidus source region and in particular on the dy- namics of porosity waves. An essential parameter controlling the width and phase velocity of porosity waves is the effec- tive shear and bulk matrix viscosity (Simpson and Spiegel- man, 2011; Richard et al., 2012). Most of the porosity wave model approaches used either equal bulk and shear viscosi- ties or simple laws in the form of
The younger gabbros show a wider variation in mineralogy and texture. They vary from medium- to coarse-grained, and from equigranular to sub-ophitic or moderately foliated. Many samples are essentially bimineralic, being composed of around 30-50 % clinopyroxene and 50-70 % plagioclase. The clinopyroxenes, which vary in composition from diopside to augite, typically have a dusky appearance due to fine exsolution textures. They are commonly partly altered to brown hornblende at the grain margins by late magmatic processes, and a few examples have large plates of poikilitic brown amphibole with little or no pyroxene present. Pervasive post-crystallisation hydrothermal alteration to pale green to colourless, fibrous (actinolitic) clinoamphibole is widespread. Plagioclase shows variable amounts of saussuritic and/or sericitic alteration.
Tasman Sea spreading center. Seamounts in diﬀerent tectonic settings show distinct patterns in the orientations of volcanic rift zones and elon- gation axes, and widespread Bouguer gravity highs broadly share these orientations, suggesting they may reﬂect the ediﬁces’ magma plumb- ing systems. These trends align closely with principal stress directions predicted by Behn et al. (2002) for a spreading center with signiﬁcant mechanical coupling across transforms ( 𝜒 = 0.10–0.15; Figure 12). This level of coupling is more likely at slow spreading systems like the Tasman Sea and is consistent with the complex, asymmetric faulting regimes com- monly observed at inside and outside corners of such regimes, with the high variability attributed to the delicate balance between magmatic and amagmatic strain (Behn et al., 2002; Bird et al., 2002; Buck et al., 2005). Across the chain, T e is also substantially lower than expected, plotting pre- dominantly on or above the 150 ∘ C isotherm with no clear age progression. Reduced T e values are often explained using viscoelastic relaxation, but this reduction is usually more modest and the T e values should retain a
At present the volcanic activity of the CVC is located in the Colima volcano while Nevado de Colima is con- sidered an extinct volcano. However, there is evidence of successive stages of activity in the latter edifice as re- cent as ~250,000 years BP, with the dating (K/Ar) of the Atenquique conglomerate derived in turn from La Calle andesite  . This andesite outcrops at the top of Nevado in an area of ~20 km 2 . Reference  re- ports an age of 9370 ± 400 yr B.P. for charcoal debris directly overlying debris avalanche deposits SE of the caldera of the ancestral Colima volcano implying that construction of the ancestral Colima volcano edifice took place before that date. In fact, these authors established a period in which the two modern structures of Nevado II-III and Paleo Fuego-Fuego were active, indicating that their contemporaneous growth poses the problem of the existence of a single reservoir feeding them, or the existence of two independent magmatic chambers after the evolution of a common, primitive volcano. The period of simultaneous activity in both structures may cor- respond to the transition period in which volcanic activity was migrating from north to south. Our models reach depths of ~20 km along L0 and suggest the existence of independent magma chambers for each volcanic edifice, which appear to be interconnected at depth. Our model thus favors the possibility of an even deeper magma chamber feeding all the more superficial ones. This deeper magma chamber is probably connected with the tec- tonic process that separates at depth the subducting Rivera and Cocos plates ; the plates begin to separate between depths of 140 - 200 km according to their horizontal, tomographic slices. However, one must bear in mind that the degraded resolution of their method at depths less than 100 km may obscure shallower phenomena. As pointed out earlier, their surface location of the place at which the Rivera and Cocos plates begin to separate at depth is slightly to the west of the Central and Northern Colima rift.
Measurement of gas emissions from volcanoes in a state of unrest can provide valuable information regarding the evo- lution of the magmatic system and play a key role in erup- tion forecasting strategies (e.g. Merapi 2010 crisis; Surono et al., 2012). In recent years, tremendous progress in instru- mentation has been made with the development of minia- ture UV spectrometers (e.g. Oppenheimer, 2010), open-path Fourier transform infrared (FTIR) spectroscopy (e.g. Hor- rocks et al., 2001) and multi-species gas-sensing systems (e.g. Aiuppa et al., 2006), making rapid measurement of all major gas species a relatively straightforward endeavour given favourable conditions.
pattern more similar to the magmatic Mountain Pass deposit ((La/Lu) cn ≈ 3900; Figure 10 ) [ 73 , 74 ].
Minerals 2018, 8, x FOR PEER REVIEW 14 of 19
as Ba. Moreover, the Mountain Pass REE deposit is a well-known example of primary euhedral barite crystals in a carbonatite. In the RFeC, the vertical geochemical variation in Cl and Ba (Figure 8) appears to reflect the intensity of hydrothermal activity. As mentioned, barite is more soluble in a Cl-rich fluid . The presence of Cl can be related to the hydrothermal fluids or can be sourced from magmatic activity [38,63]. Therefore, the upper part of the deposit, which is rich in Cl and poor in Ba, could have been exposed to more intense hydrothermal activity, resulting in extensive resorption of primary barite. Inversely, the lower part, which is richer in Ba and poorer in Cl, is interpreted as a better preserved portion that was exposed to lesser hydrothermal activity. Petrographic observations also support this lower hydrothermal activity in the lower portion of the RFeC: (1) the brecciation is significantly less intense; (2) the crystal sizes are larger; and (3) the barite crystals feature a pristine core and an altered rim (Figure 4C,F). Furthermore, the preliminary results from fluid inclusion gas analyses by solid probe mass spectrometry  revealed a progressive decrease in secondary fluid inclusions trapped in carbonates with depth . Moreover, the REE pattern of the deeper zone are typical of magmatic REE deposits such as Mountain Pass (Figure 10) [73,74]. The upper part of the RFeC has a chondrite-normalized REE pattern similar to the Bear Lodge hydrothermal-influenced carbonatite ((La/Lu) cn ≈ 540 ; Figure 10) while the deeper zone of the RFeC has a chondrite- normalized REE pattern more similar to the magmatic Mountain Pass deposit ((La/Lu) cn ≈ 3900; Figure 10) [73,74].
Japan. The magmatic influence was large inside the Unzen Graben, especially in the eastern region. The spatial variations from soil gas survey were identical to those from the groundwater survey. On the other hand, the traverse across the fault zone suggested that the fracture zone of the fault system played a key role in providing a path for a magmatic fluid from a deep environment to the ground surface. Our study shows that the soil gas survey can provide a convenient tool for the identification of magmatic influences.
Int J Dev BioI 39 51 68 (1995) Odontoblast differentiation JEAN VICTOR RUCH*, HERVE LESOT and CATHERINE BEGUE KIRN Institut de 8iologie Medica/e, INSERM U 424, Strasbourg, France CONTENTS InIrod uctio[.]
Some relationships between two quantities or variables are so complicated that we sometimes introduce a third quantity or variable in order to make things easier to handle. In mathematics this third quantity is called a parameter. Instead of one equation relating say, x and y, we have two equations, one relating x with the parameter, and one relating y with the parameter. In this unit we will give examples of curves which are defined in this way, and explain how their rates of change can be found using parametric differentiation.
The source of the carbon may be graphite which is present in hornfelses and the basement mica schists. Low salinity fluids in Older Pegmatites, quartz veins and hornfelses could have formed from low salinity late magmatic fluids. However, some mixing took place between magmatic fluids and metamorphic fluids to form CO 2 -H 2 O inclusions. High salinity magmatic fluids are only associated with
The second problem can be partially resolved by using melt and fluid inclusion studies for samples representative of magmatic-hydrothermal transition (see reviews in Roedder, 1992; De Vivo and Frezzotti, 1994; Lowenstern, 1995; Frezzotti, 2001). These are not necessarily intrusive or volcanic rocks that host mineralisation or bear hydrothermal alteration. In theory and in practice, any magma that is saturated in volatiles can further evolve by losing volatiles during degassing or separation of immiscible volatile-rich melts. At this point silicate melts and their immiscible volatile- rich products coexist and can be preserved if trapped as inclusions by crystallising minerals (e.g., Roedder and Coombs, 1967; Reyf and Bazheyev, 1977; Harris, 1986; Naumov et al., 1990; Lowenstern et al., 1991; Solovova et al., 1991; Frezzotti, 1992; Solovova et al., 1992; De Vivo et al., 1993; Lowenstern, 1993; Yang and Bodnar, 1994; De Vivo et al., 1995; Reyf, 1997; Kamenetsky et al., 1999; Thomas et al., 2000; Davidson and Kamenetsky, 2001; Fulignati et al., 2001). Such inclusions are still magmatic in nature but their compositions are much closer to hydrothermal solutions as potentially ore-forming elements preferentially partition into late magmatic immiscible phases ( e.g., Candela and Holland, 1984; Shinohara, 1994; Webster, 1997).
To constrain the seismic interpretation, it is recommended to measure the elastic and anelastic rock properties of small rock specimens in the laboratory under in situ pressure, tem- perature, and fluid content conditions. However, in mag- matic geothermal systems, the host rock is often highly im- permeable and the fluid transport predominately takes place within macro-fracture networks, rather than through the ma- trix. Such fractures are not present in the rock samples inves- tigated in the laboratory, due to their limited size. Therefore, laboratory experiments only provide the properties of rela- tively intact rock and indicators for the presence or absence of fluids need to be deduced from fluid–rock interactions at larger scales through rock physics concepts. Various such concepts of differing complexity have been used over the last 20 years to interpret seismic tomograms from geothermal ex- ploration campaigns in magmatic environments.