Cinder Cones Research Articles

Nursery Cultural Techniques Facilitate Restoration of Acacia koa Competing with Invasive Grass in a Dry Tropical Forest

Anthropogenic activity has caused persistent and prominent losses of forest cover in dry tropical forests. Natural regeneration of forest trees in grazed areas often fails due to lack of seed sources and consumption by ungulates. To address this, the effective restoration of such sites often requires fencing and outplanting nursery-grown seedlings. In the degraded, dry forests of tropical Hawaii, USA, an additional challenge to restoration of native forest trees is the introduced kikuyu grass (Cenchrus clandestinus). This invasive, rapidly growing rhizomatous plant forms deep, dense mats. We studied the use of nursery cultural techniques to facilitate the establishment of koa (Acacia koa) seedlings outplanted amidst well-established kikuyu grass on a volcanic cinder cone on the dry, western side of Hawaii Island. Seedlings were grown four months in three container sizes (49, 164, 656 cm3) and with four rates (0, 4.8, 7.2, and 9.6 kg m−3) of 15–9–12 (NPK) controlled-release fertilizer incorporated into media prior to sowing. After 16 months in the field, seedling survival was > 80% for all treatments with two exceptions: the non-fertilized 49 cm3 (78%) and 164 cm3 (24%) containers. After 10 years, only these two treatments had significantly lower survival (35% and 10%, respectively) than the other treatments. One year following planting, none of the non-fertilized seedlings had transitioned to phyllodes from juvenile true leaves, regardless of container size. For the fertilized 656 cm3 container treatment, 78%–85% of seedlings had phyllodes, with mean values increasing by fertilizer rate. Phyllodes are known to confer greater drought resistance than true leaves in koa, which may help to explain the improved survival of fertilized trees on this relatively dry site. Overall, nursery fertilization was more influential on seedling height and diameter response than container size after outplanting. However, the largest container (656 cm3) with the addition of fertilizer, produced significantly larger trees than all other treatments during the early regeneration phase; early growth differences tended to fade at 10 years due to inter-tree canopy competition. Although koa is able to fix atmospheric nitrogen through rhizobium associations, our data confirm the importance of nursery fertilization in promoting regeneration establishment. Nursery cultural techniques may play an important role in forest restoration of dry tropical sites invaded by exotic vegetation.

Morpho-chronology of monogenetic scoria cones from their level contour curves. Applications to the Chichinautzin monogenetic field, Central Mexico

The genesis, distribution and hazards associated with monogenetic volcanic fields pose particular difficulties derived from their dispersed character. Establishing a relationship between the spatial and the age distributions of volcanic cones is necessary both to understand the nature of monogenetic field formation and evolution and to set supported hazard-assessment criteria. We present here a new method –specifically developed to quantify the degree of age-dependent erosion of individual scoria cones– aimed to estimate the relative ages of undated scoria cones in a monogenetic volcanic field from a contour level morphometric analysis of the field digital elevation model (DEM). This method is based on the hypothesis that age and the degree and type of erosion causing significant morphological changes on scoria cones are markedly correlated. It is assumed that, at the time of their formation, monogenetic volcanoes have diverse, yet smooth shapes, which mechanical processes of wearing gradually change in different spatial scales. This evolution is largely evidenced both as changes of the volcano slopes and as height-dependent undulations of the cone surface generated by the hydrometeorological ablation in the otherwise uniform elevation contour lines. Here, we characterize the time-dependence of the shape and size of the altitude isoline undulations by means of the Elliptical Fourier Descriptor spectra of the contour curves of volcanic cones. To test the effects of the DEM data type and resolution on this morpho-chronological dating, we analyze the correlations of published radiometric ages of cones with two datasets of contour curves from the Sierra Chichinautzin monogenetic volcanic field in Central Mexico (SCVF): one obtained from airborne LIDAR surveys (INEGI, Mexico) and the other from a satellite radar mission (DLR, Germany).

Late Cenozoic volcanism in the Almaludag region, Azerbaijan province, northwest Iran: Evidence for post-collisional extension

We discuss the geology, petrology, and major and trace element geochemistry of Late Cenozoic volcanic rocks in the Almaludag region in the Western Azerbaijan province, northwest Iran. Geology of this region evolved through the northward subduction of the Neotethyan oceanic lithosphere and subsequent collision of the Arabian and Eurasian plates during the Alpine-Himalayan orogeny. Two different Late Cenozoic periods of volcanic activity are recognized: Episode I produced pyroclastic deposits and trachydacitic lava (1.47 Ma, U-Pb dating) and Episode II generated mafic lava and scoria cones (including spatter/cinder). Geochemical data indicate that Episode I lavas have high-silica adakitic compositions, similar to the post-collisional and continental adakites, that formed from the partial melting of the thickened lower crust. Episode II lavas vary in composition and fall into two distinct geochemical groups. The first group includes picrobasalt-basanite and tephrite compared to the more evolved trachybasalt and basaltic trachyandesite of the second group. Both of these groups show alkaline to shoshonitic affinities.The binary geochemical plots of the Episode II samples display compositional trends that indicate magmatic processes such as fractional olivine ± clinopyroxene crystallization. The major and minor elemental variations of these samples reflect a mantle source heterogeneity and minor crustal contamination. The REE (rare earth elements) patterns and spider diagrams indicate enrichment of the large ion lithophile elements (LILE) and depletion of the high field strength elements (HFSE) relative to the heavy rare earth elements (HREE), and reveal an enriched lithospheric mantle source which was previously metasomatized by subduction components. The mantle source of the Episode II lavas was enriched by fluids and melts which were released from a subducted slab between Late Mesozoic and Early Cenozoic in northwest Iran. The Si-undersaturated lavas of the first group of Episode II probably originated in the garnet stability field in the lithospheric mantle with carbonate residue or veins, suggesting that the mantle source probably underwent carbonate metasomatism. Geochemistry of the SiO2 rich lavas of the second group of Episode II is consistent with a melt extracted from a peridotitic mantle source. The compositional variation from the rocks of the first group to those in the second group suggests a diminishing degree of metasomatic veins-wallrock interactions.The Late Cenozoic mafic rocks in the Almaludag region probably formed through extension in a post-collision, post-orogenic setting. The extension was likely the result of the delamination of the thickened subcontinental lithospheric mantle (SCLM) and ensuing asthenospheric upwelling after the collision of the Arabian and Eurasian plates.

Sequence modeling in zircon double-dating of early Holocene Mt. Erciyes domes (Central Anatolia)

Abstract Mt. Erciyes (3917 m), the highest stratovolcano in Central Anatolia, Turkey, is considered active based on three recently dated early Holocene dome eruptions that were also correlated with tephras in the Mediterranean and the Black Sea. Despite the demonstrated Holocene activity of Mt. Erciyes, the eruptive chronostratigraphy of these events and their hazard potential for the nearby Kayseri metropolitan area (population ~1.4 million) remain poorly constrained. Here, we apply zircon double-dating (ZDD) based on (U–Th)/He thermochronology and U–Th–Pb crystallization ages, where intra-grain crystallization age differences were used for disequilibrium correction. Individual ZDD ages were refined via sequence modeling to reconstruct the eruption timing of four early Holocene domes peripheral to Mt. Erciyes. Sequence modeling, which incorporated petrological, volcanological, and stratigraphic constraints, yielded the following eruption ages (uncertainties stated at 1σ): 8.8 ± 0.8 ka for stratigraphically directly superimposed Perikartin and Karagullu, 8.9 ± 0.5 ka for Dikkartin, and 9.4 ± 1.3 ka for previously undated Yilanli Dag, located within the perimeter of Kayseri. A model where all four early Holocene domes are assumed to have erupted simultaneously suggests an age of 8.9 ± 0.4 ka. Earlier eruptive phases of Mt. Erciyes were identified by ZDD at ca. 85–88 ka (fall-out deposits and Carik Tepe lava) and at ca. 105 ka (xenoliths from two peripheral scoria cones). Zircon crystallization ages reveal protracted magmatic activity beneath Mt. Erciyes since ca. 800 ka, in agreement with dated volcanic activity, and preceding magmatic phases at ca. 2–3 Ma that included the eruption of the widespread Valibaba Tepe Ignimbrite with a U–Pb zircon age of 2.73 ± 0.02 Ma. A volume estimate for the Quaternary edifice of ~300 km3 translates into an integrated long-term eruptive magma flux of ~0.4 km3/ka for post-collisional Mt. Erciyes, within uncertainty of the Late Pleistocene–Holocene flux estimate of >0.1 km3/ka based on dome volumes and eruption ages. The near-synchronous eruptions of a suite of four evolved domes, in three cases with sizable early explosive venting, calls for a hazard assessment that combines the impact of multiple simultaneous eruptions.

Experimental evidence for decompression melting of metasomatized mantle beneath Colima Graben, Mexico

Primitive subduction zone magmas provide information about the composition and thermal structure of the underlying mantle wedge. In the Colima Graben, Mexico, primitive lavas erupted from cinder cones range from high magnesium calc-alkaline basalts to high-K trachybasalts. This chemical diversity suggests that the sub-arc mantle wedge from which they derive is heterogeneous. To explore the conditions of magma generation in the wedge beneath Colima we used an inverse experimental approach to constrain multiple saturation points on the liquidus surface of a primitive high-K basanite (COM-1). Equilibrium piston-cylinder experiments were carried out between 1.0 and 2.4 GPa under hydrous (1.8–3.8 wt% H2O) and oxidizing (ƒO2 = − 0.5 to 4.3 log units relative to NNO) conditions. COM-1 + 3.8 wt% H2O is shown to be multiply-saturated with a phlogopite-bearing spinel pyroxenite assemblage (cpx + opx + phl + sp) close to its liquidus at 1.9–2.4 GPa and 1300 ºC. Experimental mapping of the liquidus surface reveals a multiple saturation point (MSP) where a lherzolitic phase assemblage of ol + cpx + opx + sp + phl coexist. The topology of the MSP indicates a peritectic of the form cpx + opx + phl + sp = liquid + ol. Four bracketing experiments define the MSP of COM-1 as 1300 ± 10 °C, 1.7 ± 0.1 GPa, ∆NNO = 3.4 ± 0.5 log units, for melt containing 3.6 ± 0.4 wt% H2O. The MSP olivine is too forsterite-rich (Fo92-94) to be in equilibrium with mantle lherzolite, but matches phenocryst core compositions in the natural basanite. Thus, experimental results indicate that COM-1 was produced by incongruent melting of an olivine-free, phlogopite-pyroxenite source that itself is the result of metasomatism of mantle wedge by slab-derived fluids. These conditions provide a valuable constraint on the thermal structure and chemical composition of the mantle wedge beneath Colima.

Evidence for primitive magma storage and eruption following prolonged equilibration in thickened crust

In continental arcs, the exposure of primitive eruptive products at the surface is typically a result of rapid magmatic transfer through the crust. As a result, the initially primitive magma experiences minimal crustal residence and thus insignificant differentiation towards more evolved products. This rapid transfer of primitive magma through thickened crust is commonly recorded from smaller, monogenetic cinder cones. Manantial Pelado (35.5° S) is a long-lived stratocone in the Southern Andean Volcanic Zone (SVZ) overlying thick continental crust (45–50 km) that produces almost exclusively mafic material. As Manantial Pelado is surrounded by extensive silicic volcanism, the study of its mafic exposure as a stratocone can be used to further understand magmatic origins of long-lived volcanic systems. Our study uses textural, geochemical, and geochronological data from lavas collected from Manantial Pelado to characterize its magmatic petrogenesis, assess the primitive nature, and explain processes in the crust within the SVZ. A geologic description of the volcano reveals a mostly monotonous eruptive history of basaltic andesites that are now accessible through glacially carved valleys. New 40Ar/39Ar dating constrains most of the volcano’s cone constructing phase to last from ~ 220 to 190 ka. At ~ 30 ka, small-volume activity and different petrography of more intermediate magmas were present reflecting a change in the volcano’s character. A combination of the whole-rock and mineral-scale data reveals that basaltic andesites at Manantial Pelado are among the most primitive magmas in the thickened crust of the SVZ. Evidence for this primitive signature consists of textural and zonation patterns in olivine, the presence of Cr-spinel in olivine cores, and elevated Fo and Ni content within olivine cores. This data combined with elemental diffusion modeling provides evidence for a primitive signature for these lavas. Intermediate Fo olivines with uniform core compositions (Fo80–84) suggest that basaltic andesites reside in the crust in quasi-closed system environments for extended storage prior to eruption (~ 25–6000 years). Diffusive equilibration in those intermediate Fo olivines masks the primitive nature of the magmas. These results suggest that mafic magmas can have a protracted storage history in the crust that does not significantly alter their primitive bulk composition before reaching the surface. We argue that these are important processes in understanding the magmatic origin of long-lived systems and the presence of compositionally homogenous olivines at intermediate Fo content may represent cryptic evidence for recharge with primitive magmas that experienced prolonged crustal storage.

Growth of Grimmia mosses on volcanic tephra: Geoecological processes of biocrust development in Haleakalā crater (Maui, Hawai′i)

This research examines high-elevation biocrusts on volcanic tephra in Haleakalā Crater, Maui, Hawai′i; geomorphic, ecological, and pedological processes are discussed, in order to provide an integrated geoecological view of linkages that have influenced biocrust genesis. The study considers four spatial scales: (i) the landscape scale; (ii) the site scale; (iii) the miniature scale and, (iv) the microscopic scale. (i) Biocrusts grow at ~ 2335 m on a hydrologic basin circumscribed by four cinder cones which contributed tephra materials during eruptions between 11000 and 5000 BP, ~2700 BP, and 970 ± 50 BP. Basin landforms provide multiple clues about past geomorphic processes that have affected crust evolution, including intermittent runoff, which decreased the length of cryptobiosis periods, allowing poikilohydric mosses to gradually expand into dense biocrusts; and widespread frost activity, which caused tephra sorting and extensive slope creep on cinder cones. Ubiquitous signs of current frost disturbance are also found on basin soils. (ii) The study site, located amidst bare volcanic tephra—ash and lapilli—includes mainly two organisms: an acrocarpous moss, Grimmia torquata, and a foliose lichen, Peltigera rufescens. Biocrusts attained 40.23% groundcover;G. torquata was found on 64 undisturbed specimens, and showed 78.3% frequency on 46 sampling plots, whereas P. rufescens grew on 23.4% of specimens. Biocrusts also supported 13 vascular species. The most common were grasses, with 5.6% cover and 67.4% total frequency, including Trisetum glomeratum (47.8%) and Deschampsia nubigena (19.6%); other vascular plants reached just 0.85% combined cover. Tests show 72% of vascular-plant cover was statistically correlated with presence of biocrusts, suggesting these have beneficial—presumably pedological—effects on vascular plant growth. (iii) Biocrust microtopography was characterized by intermingling areas of rolling, 15–35 mm-high, protrusions, and 40–75 mm-high pinnacles. (iv) Soil micromorphology indicated crust growth was probably influenced by a host of genetic processes, including wind abrasion and erosion; aeolian dust deposition; soil desiccation during seasonal wet-dry cycles; rainwash and raindrop impact; diurnal temperature cycles; and bioturbation by burrowing fauna. The interactions among these agents are integrated into an idealized crust developmental sequence during the past few millennia.

Geochemical characterization of alchichica maar volcano, Serdán-oriental Basin, eastern Trans-Mexican Volcanic Belt: Insights on polymagmatic evolution at monogenetic volcanic clusters

Monogenetic volcanic fields usually comprise short-lived isolated volcanoes. However, new vents might build over or near to the older ones, resulting in the construction of complex, compound, nested, or overlapping volcanic structures formed by the superposition of individual monogenetic edifices. In the present study, we examine the case of Alchichica Maar volcano that cut through a series of pre-volcanic materials, including sheets of lava flows, pyroclastic deposits, paleosols, and scoria cone deposits. Major and trace elements are used to characterize geochemically each of the different pre-maar and maar units that integrate the Alchichica volcano, allowing to investigate the source composition, syn-eruptive, and crustal magmatic processes and the genetic relationship between the Alchichica maar and the underlying volcanic rocks. Typical lithologies are medium-K calc-alkaline rocks, including basaltic andesites for the lava flow and the scoria cone, and basalts for the maar units and the pre-maar pyroclastic unit. They also present slight variations in La/Sm, Ba/La, Zr/Nb, Ce/Yb, Ce/Pb, and Dy/Yb ratios suggesting different petrological processes such as variable amounts of partial melting in a heterogeneous spinel mantle, fractional crystallization, and crustal contamination during magma ascent. Our results reveal a polymagmatic activity, with different magma batches fed the pre-maar and the maar eruptions. They also allowed depict and confirm a time gap between the eruptive phases of the Alchichica maar formation, which is an add on the polycyclic character of the phreatomagmatic volcanism at this maar and previously described with the volcanostratigraphy examination. In addition, we conclude that the Alchichica maar cannot be defined as a polygenetic volcano; instead, it forms part of a cluster of Late Pleistocene to Holocene overlapped monogenetic volcanoes.

Hydrothermal Precipitation of Sanidine (Adularia) Having Full Al,Si Structural Disorder and Specular Hematite at Maunakea Volcano (Hawai'i) and at Gale Crater (Mars)

AbstractHydrothermal high sanidine and specular hematite are found within ferric‐rich and gray‐colored cemented basaltic breccia occurring within horizontal, weathering‐resistant strata exposed in an erosional gully of the Pu'u Poliahu cinder cone in the summit region of Maunakea volcano (Hawai'i). The cone was extensively altered by hydrothermal, acid‐sulfate fluids at temperatures up to ~400 °C, and, within strata, plagioclase was removed by dissolution from progenitor Hawaiitic basalt, and sanidine and hematite were precipitated. Fe2O3T concentration and Fe3+/∑Fe redox state are ~12 wt.% and ~0.4 for progenitor basalt and 46–60 wt.% and ~1.0 for cemented breccias, respectively, implying open‐system alteration and oxic precipitation. Hydrothermal high sanidine (adularia) is characterized by full Al,Si structural disorder and monoclinic unit‐cell (Rietveld refinement): a = 8.563(19) Å, b = 13.040(6) Å, c = 7.169(4) Å, β = 116.02(10)°, and V = 719.4(19) Å3. Hematite (structure confirmed by Rietveld refinement) is the predominant Fe‐bearing phase detected. Coarse size fractions of powdered hematite‐rich breccia (500–1000 μm) are dark and spectrally neutral at visible wavelengths, confirming specular hematite, and SEM images show platy to polyhedral hematite morphologies with longest dimensions >10 μm. Smectite and 10‐Å phyllosilicate, both chemically dominated by Mg as octahedral cation, are additional diagenetic hydrothermal alteration products. By analogy and as a working hypothesis, high sanidine (Kimberly formation) and specular hematite (Mt. Sharp group at Hartmann's Valley and Vera Rubin ridge) at Gale crater are interpreted as diagenetic alteration products of Martian basaltic material by hydrothermal processes.

Eleomelanite, (K2Pb)Cu4O2(SO4)4, a new mineral species from the Tolbachik Volcano, Kamchatka, Russia

ABSTRACT The new mineral eleomelanite, (K2Pb)Cu4O2(SO4)4, was found in the Arsenatnaya fumarole on the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik Volcano, Kamchatka, Russia. It is associated with euchlorine, fedotovite, wulffite, chalcocyanite, dolerophanite, dravertite, hermannjahnite, alumoklyuchevskite, klyuchevskite, piypite, cryptochalcite, cesiodymite, anglesite, langbeinite, calciolangbeinite, metathénardite, belomarinaite, aphthitalite, krasheninnikovite, steklite, anhydrite, hematite, tenorite, sanidine, sylvite, halite, lammerite, urusovite, and gold. Eleomelanite occurs as interrupted crusts up to 6 mm across and up to 0.3 mm thick consisting of equant, prismatic, or tabular crystals or grains up to 0.3 mm. It is translucent and black. The luster is oleaginous on crystal faces and vitreous on a cleavage surface. Dcalc is 3.790 g/cm3. Eleomelanite is optically biaxial (–), α 1.646(3), β 1.715(6), γ 1.734(6), 2Vmeas. = 60(15)°. The chemical composition (wt.%, electron-microprobe) is K2O 9.62, Rb2O 0.49, Cs2O 0.24, CaO 1.23, CuO 35.28, PbO 19.25, SO3 34.78, total 100.89. The empirical formula calculated based on 18 O apfu is (K1.88Pb0.79Ca0.20Rb0.05Cs0.02)Σ2.94Cu4.07S3.99O18. Eleomelanite is monoclinic, P21/n, a 9.3986(3), b 4.8911(1), c 18.2293(5) Å, β 104.409(3)°, V 811.63(4) Å3, and Z = 2. The strongest reflections of the powder XRD pattern [d,Å(I)(hkl)] are: 7.38(44)(101), 3.699(78)(112), , 3.173(40)(211), 2.915(35)(114), 2.838(35)(204), , and . The crystal structure was solved using single-crystal XRD data, R1 = 4.78%. It is based on heteropolyhedral Cu–S–O chains composed of Cu-centered polyhedra with [4+1+1] Cu2+ coordination and SO4 tetrahedra. Adjacent Cu–S–O chains are connected via chains of (K,Pb)O8 and KO10 polyhedra. Eleomelanite belongs to a novel structure type but has common structural features with klyuchevskite, alumoklyuchevskite, wulffite, parawulffite, and piypite. The name is derived from the Greek ελαιν (eleon), oil, and μλας (melas), black, due to its black color and oleaginous luster on crystal faces that are uncommon for sulfate minerals.

Pre-eruptive storage, evolution, and ascent timescales of a high-Mg basaltic andesite in the southern Cascade Arc

Crustal storage and transit play a critical role in the compositional evolution of arc magmas; however, the enigmatic nature of lower crustal magma storage and early differentiation limit our understanding of the connections between the physical processes of subduction zones and the architecture of the arc crust. We present new geochemical data and applications of existing barometric and chronometric tools to interrogate the mantle source compositions, crustal storage depths, and ascent timescales of a primitive, high-Mg, clinopyroxene-bearing cinder cone, the basaltic andesite of Box Canyon, located in the vicinity of Lassen Volcanic National Park, CA, in the southern Cascades. Petrographic examination in addition to bulk and in situ geochemical analyses (XRF, LA-ICP-MS, and EPMA) of tephra and lava-derived samples reveals co-crystallization of clinopyroxene and olivine as phenocrysts and glomerocrysts with ~ Mg# 80 and > Fo85, respectively. Phase equilibria experiments of analogous Cascade Arc magma compositions estimate crustal storage of the observed phase assemblage at pressures in the lower crust > 700 MPa. Reverse zonation in olivine and clinopyroxene phenocryst interiors from core-rim analytical profiles record a lower crustal mafic mixing event. Results from one-dimensional, multi-elemental olivine and clinopyroxene diffusion models fit to these interior mixing zones provide an assessment of available trace element (Ti, La, Yb, Ce, and Nd) diffusion chronometers in clinopyroxene by considering multiple element profiles within two phases that experienced the same pre-eruptive conditions. While multi-elemental and multi-phase diffusion timescales span two to three orders of magnitude, Ni in olivine profiles provide the most-robust estimate of 19.1 ± 8.6 years from mixing-to-eruption. Our results provide new constraints on arc crustal differentiation processes, indicate rapid crustal transit timescales in agreement with a growing database of diffusion-based ascent timescales of basaltic magmas, and demonstrate significant, systematic deviation of diffusion timescales calculated from natural zonation of rare earth elements in clinopyroxene and Ti in clinopyroxene and olivine.

Locally Thin Crust and High Crustal VP/VS Ratio Beneath the Armenian Volcanic Highland of the Lesser Caucasus: A Case for Recent Delamination

AbstractThe Arabia‐Eurasia continental collision created the Caucasus Mountains and the Anatolian and Iranian plateaus. Between the two plateaus, the Armenian Highland features young Holocene‐aged volcanoes. In this study, the P‐wave receiver functions from a new seismic array reveal a thick crust (up to ~52 km thick) beneath the Central Greater Caucasus and an unusually thin crust (32–35 km thick) beneath the northwestern part of Armenia near the Aragats stratovolcano and Gegham volcanic ridge formed by Pleistocene to Holocene monogenetic cinder cones. The average crustal VP/VS ratio in the Armenian Highland is anomalously high (≥1.9), with the highest value approaching 2.1 under the Gegham Ridge. Such high VP/VS ratios cannot be explained by an overall mafic crustal composition. Instead, the presence of partial melts is inferred in the lower crust based on the depth of the low‐velocity structure obtained by inversion of receiver function waveforms. Our study suggests that the postcollisional volcanism was potentially facilitated by the small‐scale removal of lithospheric mantle, resulting in a localized thinner crust balanced by thermal buoyancy and dynamic flow in the uppermost mantle beneath the Armenian Highland.

Internal Structure and Hydrothermal Fluid Circulation of Parícutin Volcano, Mexico: Insights Gained From Near‐Surface Geophysics

AbstractNumerous investigations of Parícutin volcano have been made since its formation during 1943–1952, but none has utilized geophysical techniques until now. This report summarizes the results of near‐surface geophysical surveys conducted during 2017–2019, involving self‐potential, ground‐temperature measurements, and a 3D resistivity model of the scoria cone. Interpretation of the integrated data enabled the definition of the geometry of the eruption's feeder dyke and a better understanding of the near‐surface spatter facies. These geophysical data also better characterized the buried morphology of a horseshoe‐shaped crater produced by a cone collapse early in the eruption, as well as the contact between lava flows and overlying pyroclastic fallout deposits. Moreover, the measured conductivities detected several meter‐scale zones of convective hydrothermal fluid circulation within the cone. Collectively, the data of this study demonstrate a powerful approach to discern the relationship between the internal structure of a monogenetic cone and its associated hydrothermal system.

A new mineral species zincobradaczekite, NaCuCuZn2(AsO4)3, and a new isomorphous series bradaczekite–zincobradaczekite in the alluaudite group

A new alluaudite-group mineral zincobradaczekite, a Zn–Cu ordered highly zincian analogue of bradaczekite, was discovered in sublimates of the Yadovitaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with bradaczekite, lammerite, lammerite-β, borisenkoite, mcbirneyite, sanidine, hematite, tenorite, pseudolyonsite, lyonsite, starovaite, rutile, tripuhyite, pseudobrookite, piypite, langbeinite, calciolangbeinite, aphthitalite, alumoklyuchevskite, and palmierite. Zincobradaczekite forms oblique-angled prismatic crystals up to 0.02 × 0.02 × 0.08 mm3 and equant or tabular crystals up to 0.05 mm. It is transparent, blue, greenish-blue, grey-blue or bluish-grey. The lustre is vitreous. Dcalc is 4.71 g cm−3. Zincobradaczekite is optically biaxial (–), α 1.786(5), β 1.846(8), γ 1.90(1), 2Vmeas. 80(5)o. Chemical composition (wt%, electron microprobe) is Na2O 4.07, K2O 0.53, CaO 0.01, MgO 0.71, MnO 0.01, CuO 19.89, ZnO 24.21, Al2O3 0.02, Fe2O3 0.90, TiO2 0.03, P2O5 0.41, V2O5 1.05, As2O5 47.10, SO3 1.01, and total 99.95. The empirical formula based on 12 O apfu is Na0.90K0.08Cu1.70Mg0.12Zn2.03Fe3+0.08(As2.79S0.09V0.08P0.04)Σ3.00O12. The simplified chemical formula is NaCu2Zn2(AsO4)3. Zincobradaczekite is monoclinic, C2/c, a 12.0375(13), b 12.4500(13), c 7.2213(8) A, β 117.506(7)o, V 959.90(18) A3 and Z 4. The strongest reflections of the powder XRD pattern [d,A(I)(hkl)] are 6.21(31)(020), 3.416(70)(310, − 112), 3.200(17)(002), 2.779(23)(− 402), 2.691(100)(− 132, 240), 1.841(20)(152) and 1.680(14)(− 642). The crystal structure was solved (single-crystal XRD, R = 4.38%). The simplified crystal chemical formula is A(1)□A(1)ʹCuA(2)□A(2)ʹNaM(1)CuM(2)Zn2(AsO4)3 (□—vacancy) and the end-member formula is NaCuCuZn2(AsO4)3. Zincobradaczekite and bradaczekite, ideally NaCuCuCu2(AsO4)3, are isostructural. In the Yadovitaya fumarole, Mg-poor bradaczekite forms an isomorphous series with zincobradaczekite, whilst in the neighbouring Arsenatnaya fumarole only a Zn-depleted and Mg-enriched variety of bradaczekite occurs. Zincobradaczekite and bradaczekite differ from other anhydrous alluaudite-group arsenates by increased values of the c and β unit-cell parameters due to the strong Jahn–Teller distortion of M(1)O6 octahedron predominantly occupied with Cu2+.

40Ar/39Ar step-heating dating of phlogopite and kaersutite megacrysts from the Železná hůrka (Eisenbühl) Pleistocene scoria cone, Czech Republic

40Ar/39Ar step-heating dating of phlogopite and kaersutite megacrysts from the Železná hůrka (Eisenbühl) Pleistocene scoria cone, Czech Republic

Timescales from magma mixing to eruption in alkaline volcanism in the Eifel volcanic fields, western Germany

Diffusion profiles in olivine crystals from the final mafic eruption products of the compositionally zoned Laacher See tephra deposit were measured to identify recharge and eruption-triggering events prior to the eruption of the Laacher See volcano (12.9 kyr). These products represent the hybrids of mixing between phonolite and intruding basanite at the bottom of the reservoir, which is likely related to the eruption-triggering event. Additionally, olivine crystals from ten basanitic scoria cones and maar deposits (East Eifel) and two nephelinites (West Eifel) were analyzed to constrain histories of olivine in Quaternary basanite magmas. Olivine crystals from the Laacher See hybrids vary in core composition (Fo83–89) and show reversely zoned mantles with high Fo87.8–89 compared to olivine in East Eifel basanites erupted in nearby, older scoria cones. Towards the crystal margin, olivine in the hybrids develop a normally zoned overgrowth (Fo86.5–87.5). Olivine from East Eifel basanites show similar zonation and core compositions (Fo80–88) but have less forsteritic mantles (Fo83–88) indicating that these basanites are less primitive than those recharging the Laacher See reservoir (> Fo89). Olivine in the West Eifel nephelinites show mantles similar to those from Laacher See (Fo87.5–90), but have normal zoning and high-Fo cores (Fo88–92). This indicates that olivine in the Laacher See hybrids were entrained by a near-primary basanite from older cumulates just before hybridization of the basanite with the phonolite. Diffusion modeling indicates maximum timescales between entrainment and eruption of Laacher See of 30–400 days that are comparable to those calculated for olivine from basanitic scoria cones (10–400 days).

Geomorphology of the post-caldera monogenetic volcanoes at Deception Island, Antarctica — Implications for landform recognition and volcanic hazard assessment

Deception Island is one of the most active volcanoes in Antarctica, with more than 20 monogenetic eruptions during the Holocene. The latest episodes of 1967, 1969, and 1970 have shown that volcanic activity on Deception Island can become a concern for tourists, scientists, and military personnel working on or near the island.The objective of this work is to identify eruptive processes and the geomorphic evolution of post-caldera monogenetic volcanic edifices at Deception Island by morphometric analyses, supported by field observations. Morphometric analysis has been used since the 1970s to analyse scoria cones, but it has rarely been applied to other monogenetic volcanoes, such as tuff cones and tuff rings. Tuff cones and tuff rings represent the most common landforms during Deception Island's recent geological past, with over 70 scattered eruptive vents inside and along the caldera rim. These volcanic landforms have been studied based on field observations and later, Digital Elevation Model analyses. Their geometry ranges from 10 to 100 m in height, and diameters vary between 300 and 2500 m. The morphometric data suggest that tuff cones have a more circular crater than tuff rings, with a significant separation between the two landforms using the height (Hco) and basal width (Wco) parameters. Tuff cones have Hco/Wco ratios with values between 0.04 and 0.16 and outer slopes between 7° and 34°. Tuff rings have lower Hco/Wco ratios that are between 0.01 and 0.04 and lower outer slopes between 3° and 21°.This study shows that basic shape parameters in combination with slope angle analysis can be used to discriminate among different types of monogenetic volcanoes. The initial eruptive-related morphometric diversity, however prevents correlation of eruption ages with morphometric parameters, or constructing a relative chronology of the monogenetic eruptions. This work provides a better comprehension of the potential evolution of a future eruption and a broader understanding of volcanic hazards on Deception Island.

Detailed geomorphology of debris avalanches of El Estribo volcanic complex (Central Mexico)

ABSTRACT The El Estribo Volcanic Complex, located to the south of Pátzcuaro Lake (Central Mexico), forms an elevation based on a shield volcano crowned by a cinder cone. Two debris avalanches, dated at 28,000 and 14,000 ybp, cover an area of 4 km2 with a typical hummocky topography. The zone is a state natural protected area with no previous studies of hazard and risk from mass movement processes. Herein, we present a detailed geomorphological map of the debris-avalanche area, scale 1:20,000. The approach applied used two hierarchical levels, geomorphological landscapes and landforms. The fault scarp was mapped using high-resolution digital elevation models obtained whit unmanned aerial vehicles (UAV) survey. We describe and characterized four main geomorphological units, 20 subunits, 66 hummocks, and the general drainage network. This map is a valuable tool to identify and quantify risks from mass movement processes.

Petrovite, Na10CaCu2(SO4)8, a new fumarolic sulfate from the Great Tolbachik fissure eruption, Kamchatka Peninsula, Russia

AbstractPetrovite, Na10CaCu2(SO4)8, is a new sulfate mineral discovered on the Second scoria cone of the Great Tolbachik fissure eruption. The mineral occurs as globular aggregates of tabular crystals up to 0.2 mm in maximal dimension, generally with gaseous inclusions. The empirical formula calculated on the basis of O = 32 is Na6(Na1.80K0.20)Σ2Na(Ca0.82Na0.06Mg0.02)Σ0.90(Cu1.84Mg0.16)Σ2(Na0.52□0.48)Σ1S8.12O32. The crystal-chemical formula is CuNa6−2xCax(SO4)4, which, forx≈ 0.5, results in the idealised formula Na10CaCu2(SO4)8. The crystal structure of petrovite was determined using single-crystal X-ray diffraction data; the space group isP21/c,a= 12.6346(8),b= 9.0760(6),c= 12.7560(8) Å, β = 108.75(9)°,V= 1385.1(3) Å3,Z= 2 andR1= 0.051. There are one Cu and six Na sites, one of which is also occupied by the essential amount of Ca. The Cu atom forms five Cu–O bonds in the range 1.980–2.180 Å and two long bonds ≈ 2.9 Å resulting in the formation of the CuO7polyhedra, which share corners with SO4tetrahedra to form isolated [Cu2(SO4)8]12−clusters. The clusters are surrounded by Na sites, which provide their linkage into a three-dimensional framework. The Mohs’ hardness is 4. The mineral is biaxial (+), with α = 1.498(3), βcalc= 1.500, γ = 1.516(3) and 2V = 20(10) (λ = 589 nm). The seven strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 7.21(27)(110); 6.25(38)(102); 4.47(31)(212); 3.95(21)(30$\bar{2}$); 3.85(17)(121); 3.70(36)(202); and 3.65(34)(22$\bar{1}$). The mineral is named in honour of Prof Dr Tomas Georgievich Petrov (b. 1931) for his contributions to mineralogy and crystallography and, in particular, for the development of technology for the industrial fabrication of jewellery malachite.

Tectonically controlled carbonate-seated maar-diatreme volcanoes: The case of the Volsci Volcanic Field, central Italy

Quaternary carbonate-seated maar-diatremes in the Volsci Range are one of the most intriguing products of the west-directed subduction of the Adriatic slab that drove the development of the Apennine mountain belt in Central Italy. The Volsci Volcanic Field is characterized by phreatomagmatic surge deposits, rich in accidental carbonate lithics, and subordinate Strombolian scoria fall deposits and lava flows, locally sourced from some tens of monogenetic eruptive centers (at least fifty tuff rings and scoria cones). We investigate the subsurface maar-diatreme processes in terms of relationships between faulting and explosive magma-water interaction, as well as the distribution pattern of the eruptive centers. With this aim, we present the following new data: i) description of the fold-and-thrust belt structure and associated eruptive centers, ii) componentry of volcanic rock-types, iii) determination of grain-size, degrees of whiteness and roundness of carbonate lithic inclusions, iv) micropaleontological analysis of carbonate lithics. We show that the clustering of eruptive centers is controlled by tectonic features. A first order control is tentatively related to crustal laceration and deep magma injection along a ENE-trending Quaternary lateral tear in the slab and to Mesozoic rift-related normal faults. A second-order control is provided by orogenic structures (mainly thrust and extensional faults). In particular, magma-water explosive interaction occurred at multiple levels (< 2.3 km depth), depending on the structural and hydrogeologic setting of the Albian-Cenomanian carbonates, which are intersected by high-angle faults. The progressive comminution, rounding and whitening of entrained carbonate lithics allow us to trace multistage diatreme processes. Finally, our study bears implications on volcanic hazard assessment in the region.