scholarly journals Reconnaissance geology and geophysics of the Mercurio structural dome, Chihuahua, Mexico

2019 ◽  
Vol 36 (3) ◽  
pp. 357-377
Author(s):  
Jorge Aranda Gómez ◽  
Vsevolod Yutsis ◽  
Edgar Juárez-Arriaga ◽  
Carlos Ortega-Obregón ◽  
Norma González-Cervantes ◽  
...  
Keyword(s):  
Detrital Zircon ◽  
Complex Structure ◽  
Volcanic Rocks ◽  
Normal Fault ◽  
Transitional Region ◽  
Rock Composition ◽  
Near Surface ◽  
Clastic Rocks ◽  
Sedimentary Succession ◽  
Structural Dome

The Mercurio structural dome is a poorly exposed and complex structure located in the transitional region between the Coahuila Calcareous Platform and the San Pedro El Gallo sector of the Sierra Madre Oriental, Mexico. It is located in the State of Chihuahua, close to the limits with Coahuila and Durango, Mexico. The dome is a circular structure, ~16 km in diameter, that can be seen in air-photos, satellite images, and shaded relief maps, but that has a subtle topographic expression on the ground. As seen in the field, the most conspicuous topographic features in the area are several hills with the morphology of volcanic necks that rise up to 250 m above the surrounding terrain. The deformation fringe of the dome is a series of cuesta-like low hills, less than 30 m high, where a poorly lithified volcano-sedimentary succession (litharenites, polymictic conglomerates, and ignimbrites) is almost completely masked by desert pavement, which is mainly constituted by well-rounded calcareous clasts derived from the Mesozoic sedimentary marine rocks and by less abundant Paleogene volcanic rocks exposed in the region. Inside the dome the following units are exposed: 1) the pre-volcanic basement in a NW-trending, upright, open anticline developed in limestone of the Aurora Formation, 2) a series of hills where is exposed a succession of epiclastic and volcanic rocks, which are similar, in age and lithology, to some facies of the Ahuichila Formation, and 3) a NW-trending dike, exposed at Cerro Dinamita, which is interpreted as an offshoot of the buried subvolcanic body that created the dome. The deformation fringe around the buried intrusive has a quaquaversal array in the bedding and forms a simple monocline-like structure in the NE part of the dome. A set of SE- and NW-trending plunging folds forms the SE and SW portions of the dome, respectively. The NW part of the fringe is nearly completely masked by volcanic rocks, but there is a ~W plunging syncline in the area. Geophysical data show a broad gravimetric high in the region, and there is a distinct aeromagnetic anomaly inside the dome. The morphological expression of the dome lies just east of a NW-trending lineament of gravity and magnetic anomalies, which may be the buried portion of a normal fault shown in geologic maps of the region northwest of the studied area. Another possible cause is an alignment of buried intrusive bodies suggested by the regional aeromagnetic data, a small diorite outcrop south of Sierra El Diablo, and presence of volcanic necks in the northern portion of Sierra Los Alamos. Available geological and geophysical information was used to model a near-surface, irregular intrusive body with variable magnetic susceptibilites. This variation in susceptibilities is consistent with observed differences in rock composition in the exposed volcanic rocks and with evidence that the structure was formed by a bimodal (andesite-rhyolite) magmatic system where mixing/mingling occurred. As a whole, the set of structures is interpreted as a dome formed by forceful magma injection into a previously folded Paleogene volcano-sedimentary succession. U-Pb zircon ages were used to bracket the age of the deformation pulses registered in the rocks. Litharenites from the deformed volcano-sedimentary succession yielded an Ypresian zircon age of ~51 Ma. A tilted, lithic-rich ignimbrite collected near the top of the exposed volcano-sedimentary succession has mean age of 46.4 +0.8/-1.6 Ma, and the Cerro Dinamita dike has a mean age of 29.37 ± 0.24 Ma. Thus, the youngest pulse of Laramide deformation in the area is younger than ~46 Ma and the re-folding, associated with emplacement of the dome occurred at ~29 Ma. Detrital zircon U-Pb ages from Mercurio sandstones suggest dominant sediment sources from plutonic and/or volcanic rocks exposed along western Mexico. Likely subordinate sources are Mesozoic sedimentary rocks in northern and central Mexico. Distribution of detrital zircon U-Pb ages in the studied samples is similar to that documented in sandstones of the Difunta Group at the Parras and La Popa basins, except that older grains (>1.0 Ga), documented in the clastic rocks of these basins, are scarce in the sandstones of the Mercurio area.

The Application of Seismic Reflection Techniques for Subsurface Mapping in the Precambrian Shield near Flin Flon, Manitoba

1975 ◽  
Vol 12 (12) ◽  
pp. 2036-2047 ◽  
Author(s):  
Z. Hajnal ◽  
Mel R. Stauffer
Keyword(s):  
Seismic Reflection ◽  
Complex Structure ◽  
Volcanic Rocks ◽  
Field Studies ◽  
Low Velocity ◽  
Near Surface ◽  
Precambrian Shield ◽  
Rock Types ◽  
Flin Flon ◽  
Subsurface Mapping

Some of the conditions necessary for the use of seismic reflection techniques for subsurface mapping in Precambrian Shield terranes have been determined from field studies carried out near Flin Flon, Manitoba.In areas of unconsolidated overburden, geoflex-type surface energy sources provide sufficient energy. However, in outcrop regions, boreholes have to be drilled to a minimum depth of 1.5 m, preferably in patterns of 2–6 holes. Explosives with a higher detonation velocity than those presently available would be useful.A near-surface, low velocity layer was discovered on top of all examined rock types, and appears to be the result of open fractures in the rock. The thickness of this layer varies from 20–44 m in the rocks studied.A velocity contrast of 783.3 m/s exists between the Amisk volcanic rocks and Missi sedimentary rocks, making reflection mapping possible. Seismic events which were interpreted as reflections were identified, near contacts between these formations in the subsurface. A fault contact between Amisk and Missi rocks has been mapped to a depth of about 1.6 km, and a normal stratigraphic contact between the Amisk and Missi Groups has been mapped to a depth of about 0.25 km.Because of the complex structure in most Precambrian Shield terranes, it is necessary to locate seismic lines carefully with respect to the geological features being studied. In particular, it is best to keep the line within a rock unit that has constant velocity throughout, and to use short lines, so that a limited number of structures are intersected.

scholarly journals Metamorphic gabbro and basalt in ophiolitic and continental nappes of the Zermatt region (Western Alps)

2021 ◽  
Vol 114 (1) ◽  
Author(s):  
Kurt Bucher ◽  
Ingrid Stober
Keyword(s):  
Volcanic Rocks ◽  
Western Alps ◽  
Rock Composition ◽  
Rock Interaction ◽  
Near Surface ◽  
Hp Metamorphism ◽  
Alteration Processes ◽  
Rock Alteration ◽  
Shallow Crust ◽  
Basic Rocks

AbstractThe composition of meta-gabbro and meta-basalt occurring abundant and widespread in all nappes of the nappe stack exposed in the Zermatt region of the Western Alp shows distinct patterns related to the geodynamic origin of metamorphic basic rocks. Eclogitic meta-basalts of the ophiolitic Zermatt-Saas Unit (ZSU) show enriched MORB signatures. The meta-basalts (eclogites) of the continental fragment of the Theodul Glacier Unit (TGU) derive from pre-Alpine metamorphic continental intraplate basalts. Meta-basalts (eclogites) from the continental basement of the Siviez-Mischabel nappe (SMN) derive from MORB thus a genetic relation to the TGU eclogites can be excluded. All basic igneous rocks experienced post-magmatic alteration by fluid-rock interaction ranging from processes at the seafloor, in the shallow crust, during subduction zone hydration, in the exhumation channel and late Alpine regional metamorphisms. The consequences of these alteration processes can be identified at various levels in the rock composition data. It was found that the REE data are little affected by fluid-rock alteration. Some trace elements, notably Cs, Rb, and Ba are typically massively altered relative to igneous compositions in all three groups of meta-basalts. Generally, meta-basalts from the TGU and the SMN preserved the features of the original composition whilst the ZSU meta-volcanic rocks experienced massive alteration. For the ZSU meta-volcanic rocks it is evident that Zr was gained and Y lost during high-pressure fluid-rock interaction indicating a mobile behavior of the two elements during HP-metamorphism in contrast to their behavior in hydrothermal near-surface fluid-rock interaction.

scholarly journals Volcanism in The Pre-Semilir Formation at Giriloyo Region; Allegedly as Source of Kebo-Butak Formation in the Western Southern Mountains

2019 ◽  
Vol 4 (3) ◽  
pp. 217
Author(s):  
Sri Mulyaningsih ◽  
Muchlis Muchlis ◽  
Nur W.A.A.T. Heriyadi ◽  
Desi Kiswiranti
Keyword(s):  
Hanging Wall ◽  
Volcanic Rocks ◽  
Normal Fault ◽  
Geological Mapping ◽  
Surface Mapping ◽  
Clastic Rocks ◽  
Volcanic Sequence ◽  
Rock Formations ◽  
Basaltic Composition ◽  
Absolute Age

Kebo-Butak Formation was known to be the oldest volcanic rocks limited in regional terms in the lower Baturagung Hills, Gedangsari area, Gunungkidul Regency. The main constituents of the Kebo-Butak Formation consist of intersection of volcanic-clastic rocks and calcareous sediments, locally also found basalt lava with pillow structures; which distinguished it from other volcanic rock formations in the Southern Mountains. This study aims to determine the relationship of volcanic rocks exposed in Giriloyo with the Kebo-Butak Formation in the Baturagung Hills; the chronostratigraphy and the history of volcanic  activities that produced the volcanic rocks of Giriloyo. This research was approached by volcanic geological mapping using surface mapping suported by gravity anayses. From the bottom to the top of the frontier areas result volcaniclastic rocks consisting of black tuffs with several fragments of volcanic bombs with basalt composition intersecting with thin basaltic lava inserted by calcareous claystone having an age of N5-7 (Early Miocene); pyroxene-rich basalt volcanic sequence consists of thick layers of tuff with creamy-brown color intersecting with lava and breccia inserted by calcareous sandstone aged N7-8; dikes, lava and agglomerates with basaltic composition and lava and agglomerates with andesitic composition. Stratigraphically, the volcanic rocks exposed at Giriloyo correlated with the volcanic rocks exposed at Karangtalun (Wukirsari) were under the Semilir Formation, bordered with normal fault N210oE/77o, the hanging wall composed by light grey tuff of Semilir Formation. Gravity analyses found high anomalies below the Semilir Formation exposed at Karangtalun-Munthuk (east of study area) continued to below the Giriloyo area. The high anomalies were identified as the igneous/ignimbrite volcanic sequence. Descriptively and stratigraphically, the Giriloyo volcanic sequence are a part of Kebo-Butak Formation. The petrogenesis of the volcanic rocks will be discussed in further research to interpret magmatological properties, the evolving paleo-volcano, and the absolute age of the rocks.

scholarly journals Seismic and gravity constraints on the crustal architecture of the Intermontane terranes, central Yukon

2017 ◽  
Vol 54 (7) ◽  
pp. 798-811 ◽  
Author(s):  
Andrew J. Calvert ◽  
Nathan Hayward ◽  
Rajesh Vayavur ◽  
Maurice Colpron
Keyword(s):  
Large Scale ◽  
Upper Cretaceous ◽  
Volcanic Rocks ◽  
Three Dimensional ◽  
Flower Structure ◽  
Alluvial Deposits ◽  
Near Surface ◽  
Clastic Rocks ◽  
Reflection Data ◽  
First Arrival

In 2004, two seismic reflection lines were shot across the Mesozoic Whitehorse trough and adjacent terranes. Three-dimensional first-arrival tomographic inversion is used to constrain lithology to 800–1200 m depth, and surface structures are extrapolated into the middle crust using the coincident reflection data. In the Yukon–Tanana terrane, the metasedimentary Snowcap assemblage is characterized by velocities of 4.5–5.5 km/s, while in Quesnellia, velocities of 5.0–6.0 km/s occur at 500 m depth, and probably represent igneous rocks of the Tatchun batholith. Across the Whitehorse trough, velocities >4.0 km/s correspond to clastic rocks of the Jurassic Laberge and Triassic Lewes River groups; velocities <4.0 km/s probably present the clastic Jurassic to Cretaceous Tantalus Formation. Several near-surface units with velocities of 2.0–3.0 km/s are identified; some correlate well with volcanic rocks of the Upper Cretaceous Carmacks Group, but others could be attributable to alluvial deposits or faulting. The Big Salmon fault is interpreted to dip southwest, implying that rocks of the Yukon–Tanana terrane extend beneath Quesnellia. Stikinia and Quesnellia underlie up to 5–8 km of Triassic to Early Cretaceous sedimentary strata, and appear to be a single allochthon within an 18–20 km deep synform above the Yukon–Tanana terrane, which we name the Northern Intermontane synform. In general, reflection geometries in the upper crust are complex, but are consistent with large-scale imbricate structures that have been dissected into numerous blocks by displacement along moderately to steeply dipping strike-slip faults, which may be part of a crustal-scale flower structure extending to the base of the crust.

scholarly journals Morphotectonic Analysis along the Northern Margin of Samos Island, Related to the Seismic Activity of October 2020, Aegean Sea, Greece

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 102
Author(s):  
Paraskevi Nomikou ◽  
Dimitris Evangelidis ◽  
Dimitrios Papanikolaou ◽  
Danai Lampridou ◽  
Dimitris Litsas ◽  
...  
Keyword(s):  
Fault Zone ◽  
Seismic Activity ◽  
Volcanic Rocks ◽  
Active Tectonics ◽  
Normal Fault ◽  
Aegean Sea ◽  
Northern Margin ◽  
The North ◽  
Eastern Aegean ◽  
Half Graben

On 30 October 2020, a strong earthquake of magnitude 7.0 occurred north of Samos Island at the Eastern Aegean Sea, whose earthquake mechanism corresponds to an E-W normal fault dipping to the north. During the aftershock period in December 2020, a hydrographic survey off the northern coastal margin of Samos Island was conducted onboard R/V NAFTILOS. The result was a detailed bathymetric map with 15 m grid interval and 50 m isobaths and a morphological slope map. The morphotectonic analysis showed the E-W fault zone running along the coastal zone with 30–50° of slope, forming a half-graben structure. Numerous landslides and canyons trending N-S, transversal to the main direction of the Samos coastline, are observed between 600 and 100 m water depth. The ENE-WSW oriented western Samos coastline forms the SE margin of the neighboring deeper Ikaria Basin. A hummocky relief was detected at the eastern margin of Samos Basin probably representing volcanic rocks. The active tectonics characterized by N-S extension is very different from the Neogene tectonics of Samos Island characterized by NE-SW compression. The mainshock and most of the aftershocks of the October 2020 seismic activity occur on the prolongation of the north dipping E-W fault zone at about 12 km depth.

scholarly journals Reservoir characteristics in the Cretaceous volcanic rocks of Songliao Basin, China: A case of dynamics and evolution of the volcano-porosity and diagenesis

2018 ◽  
Vol 37 (2) ◽  
pp. 607-625 ◽  
Author(s):  
Haitao Sun ◽  
Dakang Zhong ◽  
Weijia Zhan
Keyword(s):  
Volcanic Rocks ◽  
Songliao Basin ◽  
Pyroclastic Rock ◽  
Rock Composition ◽  
Volcanic Tuff ◽  
Volcanic Breccia ◽  
Pore Evolution ◽  
Diagenetic Evolution ◽  
Pore Types ◽  
Volcanic Reservoirs

To explain the strong spatial heterogeneity of volcanic reservoirs porosity in the Songliao Basin and provide new ideas for predicting good volcanic reservoirs in other similar basins, the relationship between the pore evolution process and lithology of volcanic reservoirs has been described in this article. With the description and interpretation of core, thin section, scanning electron microscope, and the results of mercury injection experiment, this article clarifies the lithology, pore types, and pore structure features of the volcanic reservoirs in the Songliao Basin. The rocks of volcanic reservoirs in study area contain pyroclastic rock and volcanic lavas. The most common lithologies are rhyolite, volcanic breccia, and volcanic tuff. The pore size, morphology, and structure vary greatly between these three lithologies, the reason of which we think is the different volcanic eruption process as well as rock composition and its structure. The digenetic evolution of rhyolite includes gas dissipation of magmatic condensation; vesicles fulfilling by hydrothermal fluid; kaolinization and sericitization of feldspar phenocrysts; carbonation, devitrification, and recrystallization of felsic matrix; and finally, the dissolution of feldspar phenocrysts and felsic matrix. As for volcanic breccia, it usually go through the compaction, quartz and calcite filling the original pores between volcanic breccias, and dissolution of mineral debris together with tuff matrix. Similar with the rhyolite, volcanic tuff also undergoes the carbonation and kaolinization of felsic matrix, the dissolution of feldspar and felsic matrix, and compaction. Due to these comprehensive processes, a comprehensive analysis of volcanic rock lithology, which can indicate lithology distribution vertically and horizontally, is very necessary during volcanic reservoirs evaluation and prediction. These detailed analyses will help explorers to find potential reservoirs by distinguishing the diagenetic evolution and pore characteristic of volcanic reservoirs.

scholarly journals PHYSICAL-MECHANICAL PROPERTIES OF METAVOLCANIC ROCKS OF THE MOUNTAIN CRIMEA

2018 ◽  
Vol 13 (4-5) ◽  
pp. 36-51
Author(s):  
J. V. Frolova ◽  
V. V. Ladygin ◽  
E. M. Spiridonov ◽  
G. N. Ovsyannikov
Keyword(s):  
Mechanical Properties ◽  
Magnetic Susceptibility ◽  
Volcanic Rocks ◽  
Low Grade ◽  
Secondary Mineral ◽  
Grade Metamorphism ◽  
Clastic Rocks ◽  
Metavolcanic Rocks ◽  
Physical Density ◽  
Characteristic Values

The article considers the petrogenetic features of the volcanogenic rocks of the Middle Jurassic age of the Mountain Crimea and analyzes their influence on physical (density, porosity, water absorption, and magnetic susceptibility) and physical-mechanical properties (strength, modulus of elasticity, and Poisson's ratio). Among volcanogenic strata there are subvolcanic, effusive and volcanogenic-clastic rocks. All volcanic rocks were altered under the influence of the regional low-grade metamorphism of the zeolite and prehnite-pumpellyite facies, which resulted in a greenstone appearance. Among the secondary mineral the most common are albite, chlorite, quartz, adularia, sericite, calcite, pumpellyite, prenite, zeolites, epidote, sphene, and clay minerals. It is shown that low-grade metamorphism is characterized by heterogenious transformations: there are both slightly modified, practically fresh differences, and fully altered rocks. Tuffs are usually altered to a greater extent than effusive and subvolcanic rocks. In general, effusive and volcanogenic-clastic rocks differ markedly in their physicalmechanical properties, which is due to the peculiarities of their formation: the former are substantially more dense and stronger, less porous and compressible. However, these differences are leveled as a result of intensive changes in mineral composition and porosity in the process of low-grade metamorphism. The most characteristic values of metavolcanite properties were revealed. It is shown that among all studied parameters, the magnetic susceptibility most clearly correlates with the degree of rocks alteration.

scholarly journals THE LOWER SILURIAN TERRIGENOUS DEPOSITS OF THE LAOELING-GRODEKOVO TERRANE (SOUTH PRIMORYE): MATERIAL COMPOSITION AND FORMATION SETTINGS

2021 ◽  
pp. 25-44
Author(s):  
A.I. Malinovsky ◽  
◽  
V.V. Golozubov ◽  
Keyword(s):  
Sedimentary Basin ◽  
Volcanic Rocks ◽  
Source Area ◽  
Island Arc ◽  
Material Composition ◽  
Recycling Rate ◽  
Composition Analysis ◽  
Rock Composition ◽  
South Primorye ◽  
Genetic Interpretation

This paper studies the original results of the material composition analysis of the Early Silurian terrigenous deposits of the Kordonka formation of the Paleozoic – Early Mesozoic Laoeling-Grodekovo terrane of the South Primorye. The research is aimed at reconstructing paleogeodynamic setting of the deposition of sediments of the formation, and determining the type and mother rock composition of the feed sources based on the complex genetic interpretation of the material composition of rocks. It was established that mineralogically and geochemically formation of the rocks correspond to the typical graywackes and represent petrogenic or “first cycle” rocks formed mainly through the source rock failure. They are characterized by a low maturity, low lithodynamic recycling rate of mother rocks and their rapid burial. The interpretation of the results of the complex study of the material composition of the rocks was carried out on the basis of its comparison with the compositions of ancient rocks and modern sediments formed in the well-known geodynamic settings. The obtained data indicate that deposits of the Kordonka formation accumulated in a sedimentary basin connected with an oceanic island arc. Being built by basic and intermediate volcanic rocks as well as by igneous and sedimentary rocks that constituted its base, this island arc was the source area that supplied clastic material to the aforementioned sedimentary basin.

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