Papers by Ivan Petrinovic
Bajo el título genérico de "Geología de los Andes Centrales Meridionales: El Noroeste Argent... more Bajo el título genérico de "Geología de los Andes Centrales Meridionales: El Noroeste Argentino" se recopilan un conjunto de trabajos realizados en los últimos años en sectores del Noroeste Argentino. Las investigaciones realizadas se localizan en la región andina de ...
Journal of Volcanology and Geothermal Research, 2006
Two Pleistocene eruptions are studied, linked to an increment in the tectonic activity of an exte... more Two Pleistocene eruptions are studied, linked to an increment in the tectonic activity of an extensive system related to Calama Olacapato El Toro Fault (COT Fault). The first one, consisting of dense pyroclastic flows and pyroclastic surges interbedded with fall deposits, was caused by a phreatoplinian eruption. The second one, consisting of a succession of pyroclastic surges, derived from a phreatic eruption. Both eruption vents have been located in en echelon normal faults with an NNE trend, and conjugated to strike faults following an NNW trend. In both episodes pyroclastic deposits and ballistic blocks follow an E SSE trend, the direction to which the fault planes and topographical slope lean. The obsidianic deposit filling the first eruption vent has the same trend and dip as the main fault plane and provides (preliminary) evidences of syntectonic emplacement. On the other hand, pyroclastic surge deposits linked to the second episode offer evidences of syndepositional faulting with listric growth faults. It is concluded that this local horizontal area linked to the COT fault was intensely active during the Pleistocene and triggered both eruptions.
Journal of Volcanology and Geothermal Research, 2006
Two Pleistocene eruptions are studied, linked to an increment in the tectonic activity of an exte... more Two Pleistocene eruptions are studied, linked to an increment in the tectonic activity of an extensive system related to Calama–Olacapato–El Toro Fault (COT Fault). The first one, consisting of dense pyroclastic flows and pyroclastic surges interbedded with fall deposits, was caused by a phreatoplinian eruption. The second one, consisting of a succession of pyroclastic surges, derived from a phreatic eruption. Both eruption vents have been located in en echelon normal faults with an NNE trend, and conjugated to strike faults following an NNW trend. In both episodes pyroclastic deposits and ballistic blocks follow an E–SSE trend, the direction to which the fault planes and topographical slope lean. The obsidianic deposit filling the first eruption vent has the same trend and dip as the main fault plane and provides (preliminary) evidences of syntectonic emplacement. On the other hand, pyroclastic surge deposits linked to the second episode offer evidences of syndepositional faulting with listric growth faults. It is concluded that this local horizontal area linked to the COT fault was intensely active during the Pleistocene and triggered both eruptions.
The morphometry of volcanic edifices reflects the aggradational and degradational processes that ... more The morphometry of volcanic edifices reflects the aggradational and degradational processes that interact during their evolution. In association with VOGRIPA, a global risk identification project, we are currently constructing a database on the morphometry of volcanic edifices using digital elevation models (DEMs) from the Shuttle Radar Topography Mission (SRTM). Our aim is to compile and make available a global database of morphometric parameters that characterize the shape and size of volcanic edifices. The 90-meter SRTM DEM is presently the best public-access DEM dataset for this task because of its near-global coverage and spatial resolution that is high enough for the analysis of composite volcanic edifices. The Smithsonian Institution database lists 1536 active/potentially active volcanoes worldwide. Of these, ~900 volcano edifices can be analyzed with the SRTM DEMs, discarding volcanoes not covered by the dataset above latitudes 60°N and 56°S, submarine volcanoes, volcanoes with mostly negative topographies (i.e. calderas, maars) and monogenetic cones and domes, which are too small to accurately study with the 90-meter resolution. Morphometric parameters are acquired using an expressly written IDL-language code named MORVOLC. Edifice outline is determined via a semi-automated algorithm that identifies slope-breaks between user-estimated maximum and minimum outlines. Thus, volcanic edifices as topographic entities are considered, excluding aprons or ring plains and other far-reaching volcanic products. Several morphometric parameters are computed which characterize edifice size and shape. Size parameters are height (from base to summit), volume, base and summit areas and widths (average, minimum, maximum). Plan shape is summarized using two independent dimensionless indexes that describe the shape of the elevation contours, ellipticity (quantifies the elongation of each contour) and irregularity (quantifies the irregularity or complexity of each contour). Profile shape is summarized using dimensionless ratios (height/basal width, summit width/basal width) and slope statistics (mean, maximum interval, slope variation vs. height). A degree of radial symmetry is also calculated, as well as the azimuth of edifice elongation, the strike and dip of the basal surface and the number of summit and flank peaks. In addition to the morphometric parameters, graphs, profiles and maps are also generated. We anticipate that the database will be useful for regional comparisons, for quantitative and systematic classifications, and as a tool for studies of associated volcanological processes (e.g. Grosse et al., 2009, Geology).
Geology, 2009
... volcano types has been studied in detail, such as cinder cones (eg, Wood, 1980; Riedel et al.... more ... volcano types has been studied in detail, such as cinder cones (eg, Wood, 1980; Riedel et al., 2003), oceanic shields (eg, Cullen et al ... 4). Within this large cone subgroup is a set of paired or twin cones (Atitlán-Tolimán, Fuego-Acatenango, and San Pedro–San Pablo), which are ...
Journal of Volcanology and Geothermal Research, 2010
Polygenetic, silicic collapse calderas are common in the central Andes. Here we describe in detai... more Polygenetic, silicic collapse calderas are common in the central Andes. Here we describe in detail the Cerro Aguas Calientes caldera in NW Argentina, which comprises two caldera-forming episodes that occurred at 17.15 Ma and 10.3 Ma. We analyse the significance of its structural setting, composition, size and the subsidence style of both caldera episodes. We find that the caldera eruptions had a tectonic trigger. In both cases, an homogeneous dacitic crystal-rich (>60 vol.% of crystals) reservoir of batholithic size became unstable due to the effect of increasing regional transpression, which favoured local dilation through minor strike–slip faults from which ring faults nucleated and permitted caldera collapse.Both calderas are similar in shape, location and products. The 17.15 Ma caldera has an elliptical shape (17 × 14 km) elongated in a N30° trend; both intracaldera and extracaldera ignimbrites covered an area of around 620 km2 with a minimum volume estimate of 140 km3 (DRE). The 10.3 Ma episode generated another elliptical caldera (19 × 14 km), with the same orientation as the previous one, from which intracaldera and outflow ignimbrites covered a total area of about 1700 km2, representing a minimum eruption volume of 350 km3(DRE).In this paper we discuss the significance of the Cerro Aguas Calientes caldera in comparison with other well known examples from the central Andes in terms of tectonic setting, eruption mechanisms, and volumes of related ignimbrites. We suggest that our kinematic model is a common volcano-tectonic scenario during the Cenozoic in the Puna and Altiplano, which may be applied to explain the origin of other large calderas in the same region.
Earth and Planetary Science Letters, 2001
The evolution of Andean volcanism including the formation of late Miocene to Recent collapse cald... more The evolution of Andean volcanism including the formation of late Miocene to Recent collapse calderas on the Puna plateau is generally interpreted in terms of the kinematic framework of the Nazca and South American Plates. We present evidence that caldera dynamics and associated ignimbrite volcanism are genetically linked to the activity of first-order NW–SE-striking zones of left-lateral transtension on the local and regional scales. Consequently, ages of collapse calderas indicate activity of these fault zones which initiated at about 10 Ma on the Puna plateau. The onset of such faulting points to a change in the deformation regime from dominantly vertical thickening to orogen-parallel stretching upon reaching maximum crustal thickness and critical surface elevation. Horizontal magma sheets that formed at mid-crustal level possibly due to heat advection by volume increase of asthenospheric mantle below thickened crust were tapped by sub-vertical faults. This accounts well for the observed tectono-magmatic phenomena at surface. It follows that formation of collapse calderas and eruption of voluminous ignimbrites appear to be related to the mechanical evolution of the Andean plateau rather than to changes in the geometry of the Wadati–Benioff zone or plate boundary kinematics.
Sedimentary Geology, 2010
Variations in clay–mineral assemblages in ancient continental deposits are frequently used to rec... more Variations in clay–mineral assemblages in ancient continental deposits are frequently used to reconstruct past climate changes. In active settings, volcanic events can supply highly labile volcaniclastic material, which can easily be transformed into smectite via diagenesis, which can produce a noticeable footprint in clay–mineral assemblages. Southern Central Andean foreland deposits are appropriate case studies to ascertain whether the climatic signal was preserved in the clay assemblages of their fine-grained sediments as tectonic uplift, volcanism, and sedimentation have been interacting since the Cretaceous. We have studied a 1400-m-thick coarsening-upward Palaeogene succession of the Tin Tin basin (northern Calchaquí Valley, Argentina), applying X-ray diffraction (XRD), electron microscopy, and detailed sedimentary facies analysis with the aim of comparing tendencies in the vertical fluctuations of clay minerals with evidence from sedimentological facies.Illite–muscovite plus smectite account for 78% to 100% of the clay minerals in the fine fraction, with kaolinite and chlorite in subordinate amounts. The vertical variation of sedimentary settings from an overbank/lacustrine domain to fluvial braided plains and an aeolian dune field suggests a gradual increase in aridity upsection. However, smectite abundances do not show a gradual decreasing trend compatible with progressively lower hydrolyzing conditions; their relative abundances vary widely throughout the section, depicting pulse-like, abrupt fluctuations. Despite the absence of field evidence for volcanic influence, several indications of volcanic and volcaniclastic material have been found under scanning electron microscopy (SEM) in levels with high smectite abundances from the middle to the top of the succession. They include quartz crystals showing embayments and skeletal forms, with smectite filling the voids, microcrystalline silica, as well as heulandite crystals in close association with authigenic smectite. The XRD analyses of these levels evidence well-crystallized smectite, which is characteristic of a volcaniclastic origin. Therefore, the increase in smectite abundance in these beds reflects a significant volcaniclastic contribution, which is also evidenced by a centimetre-thick ash layer topward in the sequence. The only smectite-rich level near the base of the Tin Tin section also contains well-crystallized smectite associated with heulandite, thus probably evidencing volcaniclastic input. We infer that most of the smectite in these sediments formed during early diagenesis, probably through the dissolution of labile tuffaceous material. Textural and morphological analysis by SEM is essential to determine whether clay–mineral assemblages could be interpreted in terms of palaeoclimate.
Journal of South American Earth Sciences, 2005
The Catalão I carbonatite complex, central Brazil consists of ultramafic silicate rocks with subo... more The Catalão I carbonatite complex, central Brazil consists of ultramafic silicate rocks with subordinate carbonatite and associated phoscorite, nelsonite, and monazitite. In the Lagoa Seca area, lacustrine sediments discordantly overlie a 15-m thick unit of horizontally layered alkaline rocks that consist of a basal apatitite/nelsonite overlain by monazitite. The unit contains cylindrical to conic pipes filled with breccia, limited at the top by a discordance and at the bottom by phoscorites and carbonatites. X-ray diffraction and microprobe studies show that the pipes are filled dominantly by gorceixite and ilmenite, with subordinate apatite, calcite, pyrochlore, baryte, anatase, vivianite, and quartz and rare perovskite. This assemblage has possible primary phases and common alteration products of late-stage phoscorite-series rocks, such as carbonate nelsonites. The lower and intermediate portions of some pipes are fine grained, with cross- and coarsening-upward bedding. These structures are typical of diluted particulate flows (e.g. surges), which suggests that magma fragmentation occurred inside the chamber. The rocks and structures described here seem to represent an extreme case in which surge-like deposits formed within a conduit or even inside the magma chamber, implying that surge processes may develop at higher-than-atmospheric pressures.
Tectonophysics, 2009
The interpretation of Acocella et al. about (i) westward increase of strike-slip motion, (ii) str... more The interpretation of Acocella et al. about (i) westward increase of strike-slip motion, (ii) strain partitioning, (iii) symmetry of the Central Andes, as well as (iv) the interpreted cause for the occurrence of magmatic centres behind the arc, from the Late Miocene onward, is largely speculative and contains major flaws. We demonstrate all above, that successive phases of deformation from Middle Eocene to Quaternary in the edge of the Puna-Eastern Cordillera, as well as the occurrence of arc/intraplate signatures in the magmatic centres of the Eastern Cordillera, result in complex geological framework which requires more detailed and intensive work in order to achieve sustainable interpretations.
Iop Conference Series: Earth and Environmental Science, 2008
Chemical Geology, 2007
Peridotite xenoliths from the late-Cretaceous Alto Paranaíba and Goiás mafic–alkalic magmatic pro... more Peridotite xenoliths from the late-Cretaceous Alto Paranaíba and Goiás mafic–alkalic magmatic provinces of central and southeast Brazil reveal the existence of compositionally and temporally distinct lithospheric mantle beneath these areas. Garnet and spinel–lherzolites and spinel–harzburgites from the Alto Paranaíba province are generally depleted in Ca, Al and Re, which indicates that they are residues of melt extraction. Old Re-depletion model ages (average 2.4 Ga) for these peridotites show that this area is underlain by the early-Proterozoic to late-Archean melt-depleted lithospheric mantle of the São Francisco Craton. In contrast, spinel–lherzolites from the Goiás alkalic province, located 500–600 km northwest of the Alto Paranaiba province, have major- and trace-element compositions similar to modern fertile mantle. Most Goiás peridotites have fertile mantle 187Os/188Os (0.1261–0.1292), but two samples with lower 187Os/188Os define Re-depletion model ages of ∼ 1.2 Ga.The compositional distinction between the lithospheric mantle samples is mirrored in the kamafugitic rocks of these two provinces, which suggests that the composition of these magmas was strongly influenced, or determined entirely, by the lithospheric mantle. Most of the kamafugitic rocks have 187Os/188Os higher than observed for peridotite, which suggests that the source of these magmas is a mixture of lithospheric peridotite of varying age, veined and/or interlayered with various olivine-poor components. The relatively limited range in Sr, Nd, and Hf isotopic composition of the mafic–alkalic magmas indicates that the olivine-poor component was added regionally, overprinting the incompatible-element characteristics of the lithospheric mantle beneath these provinces. The age of metasomatism in the lithospheric mantle of this area is poorly constrained, but the isotopic characteristics of the mafic–alkalic magmatism suggest that this event may have occurred during the mid- to late-Proterozoic assembly of the Brasília mobile belt.
Journal of Volcanology and Geothermal Research, 2010
This article identifies the Pucarilla–Cerro Tipillas Volcanic Complex and its major eruptive sour... more This article identifies the Pucarilla–Cerro Tipillas Volcanic Complex and its major eruptive source, the Luingo caldera (26° 10′S–66° 40′W). Detailed geological mapping, stratigraphic sections, facies analysis and correlations, including the identification of typical caldera components, allow us to infer the position of a collapse caldera, elongated at N65° and with a diameter of 19 km × 13 km, which is responsible for an eruption of 135 km3 (DRE) of magma. The high-crystal contents of the associated ignimbrites, combined with its tectonic setting, indicate that regional and local tectonic structures played a crucial role in the formation of the caldera.The Luingo caldera is located on the south-eastern border of the Puna, and is the south-easternmost recognised caldera of the Altiplano–Puna plateau. The age of the caldera and its products is 12.1 to 13.5 Ma. Based on its location near the Cerro Galán Complex (2 to 6.5 Ma), we can imply that volcanism existed in the area for about 10 Ma. The caldera morphology and product distribution account for a middle Miocene paleao-topography similar to the present one.
Journal of Volcanology and Geothermal Research, 2006
Los Gemelos and El Saladillo are both monogenetic, strombolian, basaltic shoshonitic volcanoes th... more Los Gemelos and El Saladillo are both monogenetic, strombolian, basaltic shoshonitic volcanoes that constitute the easternmost recognized examples of mafic Plio-Quaternary volcanism in the southern Central Andes. Two regional faults delimit the borders of the Calchaquí valley, as thrusts with opposite vergence: the eastern Calchaquí fault and the western Toro Muerto fault. While Los Gemelos are set in the hanging wall of Calchaquí back-thrust fault, El Saladillo are set in the footwall of Toro Muerto fault. As Los Gemelos volcanoes have well preserved morphological features, we highlight some relationship between them and their tectonic setting. Kinematic data and one new measurement, that indicate right strike-slip movement in the vicinity of Los Gemelos during the Pleistocene Holocene. The emplacement of these volcanoes should be related to a transpression zone parallel to the valley, where the alignment of the cones is outlining the trend of conjugated faults. The magmas were derived from a small degree of partial melting of an enriched, garnet-bearing mantle source. The analysed rocks have primitive signature (high Ni, Cr, Co and MgO concentrations; presence of chromite and forsteritic olivine) and evidence for crustal contamination with felsic rocks (quartz ± plagioclase ± K-feldspar xenocrysts with coronas, reaction rims and/or embayments; high 87Sr/86Sr ratios, negative ɛNd values). The high Cr and Ni content, high Mg# and low crystal content suggest that no major fractional crystallization occurred, therefore precluding long residence periods. Rapid magma ascent across 60 km of continental crust was guided by magmatic overpressure favoured by important tectonic stresses also avoiding significant residence time at upper crust depth. Thus, we invoke a process of assimilation during turbulent ascent (ATA) to explain the contamination at crustal levels. Los Gemelos volcanoes were formed around 35,000 yr. as inferred from the age of lacustrine sediments overlying the lava flows. These ages agree well with the age of paleolakes of tectonic origin in NW Argentina, suggesting a common tectonic cause for both effects.
Tectonophysics, 2009
The interpretation of Acocella et al. about (i) westward increase of strike-slip motion, (ii) str... more The interpretation of Acocella et al. about (i) westward increase of strike-slip motion, (ii) strain partitioning, (iii) symmetry of the Central Andes, as well as (iv) the interpreted cause for the occurrence of magmatic centres behind the arc, from the Late Miocene onward, is largely speculative and contains major flaws. We demonstrate all above, that successive phases of deformation from Middle Eocene to Quaternary in the edge of the Puna–Eastern Cordillera, as well as the occurrence of arc/intraplate signatures in the magmatic centres of the Eastern Cordillera, result in complex geological framework which requires more detailed and intensive work in order to achieve sustainable interpretations.
Journal of Volcanology and Geothermal Research, 2006
This field-based and analytical laboratory study focuses on the genetic relationship between bimo... more This field-based and analytical laboratory study focuses on the genetic relationship between bimodal volcanic centres and fault types of an important tectonic transfer zone in the southern Central Andes, the NW–SE striking Calama–Olacapato–Toro (COT) volcanic belt. More specifically, tectono–magmatic relationships are examined for the 0.55 Ma Tocomar, the 0.78 Ma San Jerónimo and the 0.45 Ma Negro de Chorrillos volcanic centres in the Tocomar area (66°30 W–24°15 S). Structures of the COT volcanic belt, notably NW–SE striking strike-slip faults and NE–SW trending normal faults, accommodated differential shortening between major N–S striking thrust faults on the Puna Plateau. We present evidence that bimodal volcanism was contemporaneous with activity of these fault types in the COT volcanic belt, whereby eruption and composition of the volcanic rocks in the Tocomar and San Jerónimo–Negro de Chorrillos areas appear to have been controlled by the kinematics of individual faults. More specifically, rhyolitic centres such as the Tocomar are associated with normal faults, whereas shoshonitic–andesitic monogenetic volcanoes, e.g., the San Jerónimo and Negro de Chorrillos centres, formed at strike-slip dominated faults. Thus, the eruption of higher viscous rhyolite magmas appears to have been facilitated in tectonic settings characterized by horizontal dilation whereas ascent and effusive volcanic activity of less viscous and hot basaltic andesites to shoshonites were controlled by subvertical strike-slip faults. While the Tocomar rhyolites are interpreted to be derived from an anatectic crustal source, geochemical characteristics of the San Jerónimo and Negro de Chorrillos shoshonitic andesites are in agreement with a deeper source. This suggests that the composition of erupted volcanic rocks as well as their spatial distribution in the Tocomar area is controlled by the activity of specific fault types. Such volcano–tectonic relationships are also evident from older volcanic centres of the COT volcanic belt. This points to a close genetic relationship between bimodal volcanism and the upper-crustal deformation regime, whereby episodes of increased volcanic activity correlate with deformation episodes in the Central Andes.
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Papers by Ivan Petrinovic