Ring Fault Research Articles

Геоактивные зоны и структура растительных сообществ в связи с новыми открытиями в космической геологии

The purpose of the work is to find out how plants react to such zones and whether their phytoindication is possible. Two territories of the Perm territory were studied: the Vishersky Nature Reserve and forests near Perm. The research methodology included lineament and geostructurometric analysis of space images and special maps using ring structures discovered on the Earth’s surface by Yu. I. Fivenskii, as well as phyto- and bioindication of small geoactive zones. It was found that in the forests near Perm favorable zones of such zones occupy 1.44% of the territory and within their limits the safety of common pine (Pinus sylvestris L.) is 29–42 times higher. Phytoindication of small geoactive zones of 1.0 and 3.0 m by common pine was shown in the zones of influence of these zones: 0–18 cm — the radius of inhibition with the absence of trees; 19–29 cm — the depression zone with small trees; 30–48 cm — the comfort zone with medium and large trees. Two types of networks formed by zones of 1.0 and 8.0 m in size near Perm (on the plain) and in the reserve (in the mountains) were compared. In the mountains, with high geodynamic activity of territories, the networks are oriented in one direction, while on the plain their orientation is misaligned by 30°. In the reserve, large trees of Siberian spruce (Picea obovata Ledeb.) were located on small geoactive zones of 1.0 and 8.0 m, and trees of Siberian pine (Pinus sibirica Du Tour) — on zones 1.0 and 3.0 m in combination with zones 16, 32 and 55 m. In the subgolets zone, ring structures of perennial plants were also found on the first two types of zones. In addition, along the edges of the swamps, chains of trees were found whose direction coincides with ring faults, and the chains themselves are similar to the structure of small geoactive zones networks, and this fractality requires field verification. The hypothesis recharge of plants within geoactive zones is proposed, which also explains the successful growth of trees on rocks, where the amount of available soil is minimal.

Nonlinear resonance characteristics of a dual-rotor system with a local defect on the inner ring of the inter-shaft bearing

In this paper, the nonlinear resonance characteristics of a dual-rotor system are investigated with the consideration of a local defect on the inter-shaft bearing of the system. A simplified model of the dual-rotor system is proposed by considering that there is a local defect on the inner ring of inter-shaft bearing. The local defect is modelled as an inverted isosceles trapezoidal groove, which can make great influence on the inter-shaft bearing force due to the change of radial clearance of the inter-shaft bearing. The motion equations of the dual-rotor system are formulated by using the Lagrange equation. The Runge-Kutta method is employed to solve the motion equation. The amplitude-frequency response curve of the dual-rotor system is obtained, the abnormal resonance characteristics are analyzed. In addition, the influence of defect parameters, rotors and support parameters and inter-shaft bearing parameters on the amplitude-frequency characteristics of the system are discussed. The results show that there are two main resonance peaks and four abnormal resonance peaks on the amplitude-frequency response curve of the dual-rotor with a local defect on the inner ring of the inter-shaft bearing. Through analyzing the vibration response of the abnormal resonance peaks, it is found that the first two abnormal resonances are caused by the combined resonance, which are related to the inner ring fault and the rotational speed of high or low pressure rotors, and the last two resonances are caused by the induced resonance of the inner ring fault. At the same time, when the parameters of defect, rotors and support and inter-shaft bearing change, the resonance of the system also shows the corresponding change law.

Fault Diagnosis of Intershaft Bearing Using Variational Mode Decomposition with TAGA Optimization

To efficiently extract the features of aeroengine intershaft bearing faults with weak signal, the variational mode decomposition (VMD) method based on the tolerant adaptive genetic algorithm (TAGA) (TAGA-VMD) is proposed by introducing the idea of tolerance into the traditional adaptive genetic algorithm in this paper. In this method, the tolerant genetic algorithm was adopted to find the optimum empirical parameters K and α of VMD. A fault simulation experiment system of intershaft bearings was built for the inner ring fault and outer ring fault of bearings to verify the proposed TAGA-VMD method. The results show that the proposed method can effectively extract the fault feature frequency of intershaft bearings, and the error between the extracted fault feature frequency and the theoretical value of fault frequency is less than 0.1%. The efforts of this study provide one promising fault feature extraction approach for aeroengine intershaft bearing fault diagnosis with weak signal.

Plutonic record of a caldera-forming silicic eruption: The shatter zone of the Cadillac Mountain granite, coastal Maine

Abstract Although it is widely accepted that large silicic calderas are associated with voluminous synvolcanic intrusive complexes at depth, geological evidence for caldera-forming eruptions preserved in plutonic rocks has largely been elusive. Here, we document a rare example of such evidence in the Cadillac Mountain intrusive complex, Maine (USA), where erosion has revealed a remarkable marginal “shatter zone” that records evidence for a major caldera-forming eruption. This shatter zone, up to >1 km wide, is bounded by a steep ring fault at its outer margin, which grades inward into Cadillac Mountain granite. Its outer margins are characterized by intensely brecciated and deformed country rock injected by felsite veins, reflecting explosive fragmentation associated with eruptive decompression. This marginal facies grades inward to a chaotic mélange of variably rounded and remelted country rock blocks in granitic matrix, reflecting debris eroded from ring fault conduit walls and milled in an eruptive jet before collapsing onto crystal mush. Further inward, blocks up to 80 m in size were stoped from the collapsing chamber roof and settled onto strong mush. Textural and chemical variations in the shatter zone matrix reveal syneruptive ascent of distinct silicic and more mafic magma from depth, which was likely drawn through the highly permeable shatter zone toward areas of low pressure beneath active vents. The Cadillac Mountain shatter zone provides clear evidence for a major eruption preserved in the plutonic record and supports the origin of some granites as the cumulate roots of large silicic volcanic systems.

Fault Dynamic Modeling and Characteristic Parameter Simulation of Rolling Bearing with Inner Ring Local Defects

To further study the fault mechanism and fault features of rolling bearings, a two‐DOF rolling bearing fault dynamic model with inner ring local defects considering the bearing radial clearance and time‐varying displacement excitation is established based on Hertz contact theory. By comparing the simulated fault signal with bearing fault test data in the time domain and frequency domain, the accuracy of the established fault dynamic model is verified. Finally, the change rules of the characteristic parameters of the bearing inner ring fault signal, including effective value, absolute mean value, square root amplitude, peak value, kurtosis factor, pulse factor, peak factor, and shape factor, are simulated by the fault dynamic model. The results highlight that the proposed fault dynamic model is in good agreement with the experimental results. The model can simulate the fault signal characteristic parameters with the change of defect width, external load, and rotating speed effectively. The study in this paper is of engineering application value for bearing condition monitoring and fault diagnosis.

Research on bearing diagnosis technology based on wavelet transform and one-dimensional convolutional neural network

Aiming at the fault diagnosis of rolling element bearings, propose a method for fine diagnosis of bearings based on wavelet transform and one-dimensional convolutional neural network. First use wavelet transform to decompose the experimental data; Use the resulting low-frequency signal as a one-dimensional convolutional neural network input, bearing fault identification. The experiment uses the deep groove ball bearing of Case Western Reserve University as the research object, Use this method to identify the normal and outer ring faults of the bearing. the result shows: This method can be effectively applied to the precise identification of bearings.

Research on early weak structural damage detection of aeroengine intershaft bearing based on acoustic emission technology

Until now, there is no effective method to detect the early weak structural damage of the aero engine intershaft bearing. In this article, an online method based on acoustic emission technology is used to detect the early weak structural damage of aeroengine intershaft bearing. The combination of maximum correlated kurtosis deconvolution and bandpass filter is proposed to enhance and denoise fault characteristic signals of the aero engine intershaft bearing. The Hilbert envelope demodulation is used to extracting the bear fault characteristic frequency. Under aeroengine working conditions, the experiment of an intershaft bearing with outer ring fault is carried out. The result shows that bearing outer ring fault characteristic frequency and bearing vibration frequencies clearly appear in the envelope spectrum of the acoustic emission signal. Therefore, online detection of early weak structure damage of aeroengine intershaft bearing is realized by acoustic emission technology under the background of strong noise.

Time-varying fault feature extraction of rolling bearing via time–frequency sparsity

The joint time–frequency (TF) distribution is a critical method of describing the instantaneous frequency that changes with time. To eliminate the errors caused by strong modulation and noise interference in the process of time-varying fault feature extraction, this paper proposes a novel approach called second-order time–frequency sparse representation (SOTFSR), which is based on convex optimization in the domain of second-order short-time Fourier transform (SOSTFT) where the TF feature manifests itself as a relative sparsity. According to the second-order local estimation of the phase function, SOSTFT can provide a sparse TF coefficient in the short-time Fourier transform (STFT) domain. To obtain the optimal TF coefficient matrix from noisy observations, it is innovatively formulated as a typical convex optimization problem. Subsequently, a multivariate generalized minimax concave penalty is employed to maintain the convexity of the least-squares cost function to be minimized. The aim of the proposed SOTFSR is to obtain the optimal STFT coefficient in the TF domain for extraction of time-varying features and for perfect signal reconstruction. To verify the superiority of the proposed method, we collect the multi-component simulation signals and the signals under variable speed from a rolling bearing with an inner ring fault. The experimental results show that the proposed method can effectively extract the time-varying fault characteristics.

Monitoring temporal variations in the geothermal activity of Miocene Lesvos volcanic field using remote sensing techniques and MODIS – LST imagery

Many islands of the Aegean Sea show strong geothermal activity due to volcanism in the area. In this paper, Robust Satellite Techniques (RST) are used to isolate, from other known possible sources, those thermal anomalies possibly related to geothermal activity in the Miocene volcanic field of Lesvos Island (Northern Aegean). For this purpose, 12 years (2003–2014) of daily Night-time Land Surface Temperature (LST) products, from Moderate Resolution Imaging Spectroradiometer (MODIS) acquisitions were analyzed. The final dataset contained 770 thermal anomalies whose spatial correlation with geological and structural data of Lesvos - such as caldera rims, ring faults, major tectonic lineaments and hydrothermal alterations mapped by processing SENTINEL-2 MSI satellite images – has been particularly investigated. In the approximately 20 ma geothermal field of Lesvos, geothermal activity seems to be also associated with the extensional regime of the broader area that leads to lithosphere thinning and consequent heat transfer in the multi-fractured terrain of Lesvos through volcanic and tectonic faults. Achieved results seem to confirm the possibility to use RST-based thermal anomalies to identify temporal variations in the geothermal activity probably due to the uplifting and circulation of the hydrothermal waters.

Evolution of the Alu-Dalafilla and Borale volcanoes, Afar, Ethiopia

The Danakil depression marks a progressive change from continental rifting in Afar to seafloor spreading further north in the Red Sea. Extension and volcanism in this incipient spreading centre is localised to the ~70-km-long, 20-km-wide active Erta Ale volcanic segment. Here, we combine remote sensing and major element geochemical analysis to determine the structure and composition of three volcanoes on the Erta Ale Volcanic Segment: the Alu dome, the Dalafilla stratovolcano and the Borale stratovolcano. We investigate the evolution and compositional variation within and between these volcanic complexes. Our results show that most flows are sourced from scoria cones and fissures, representing in total 15 phases of volcanism that occurred within four major eruptive stages, most likely occurring in the last 80 thousand years (kyr). The first stage represents large-scale fissure volcanism, comprising submarine basaltic phases. Stage two involves basaltic fissure volcanism around Alu. The third stage is dominated by trachy-andesite to rhyolitic volcanism from the volcanic edifices of Alu, Dalafilla and Borale and the fourth by a resumption of small-scale basaltic/trachybasalt fissure systems. Geochemical modelling indicates a paucity of crustal assimilation and mixing within the sub-volcanic magmatic system. Spatial analysis of volcanic cones and fissures within the area indicate the presence of a cone sheet and ring faults. The fissures are likely fed by sills connecting the magma source with the volcanic edifices of Alu and Borale. Our results reveal the cyclic nature of both eruption style and composition of major volcanic complexes in rift environments, prior to the onset of seafloor spreading.

Feature extraction by enhanced analytical mode decomposition based on order statistics filter

The methods of mode decomposition based on the amplitude of spectrum are widely used in the fault diagnosis of bearings and gears in rotating machinery such as centrifuges, slurry pumps, fans, etc. Analytical mode decomposition with excellent filtering could set the bisecting frequency to distinguish useful modes. However, the vibration signal of equipment in actual operation is complex. This paper is devoted to the research of a novel spectral segmentation mode decomposition method. The proposed enhanced analytical mode decomposition takes advantage of the trend of spectrum fluctuations. In order to obtain the most critical bisecting frequency, the trend spectrum estimation method was proposed based on order statistics filter. The filtering effect of enhanced analytical mode decomposition was verified by the simulated signal. The experimental results show that the proposed method is efficient and the bearing inner and outer ring faults in the rotating machine can be successfully extracted.

Material failure and caldera collapse: Insights from the 2018 Kilauea eruption

The Failure Forecast Method (FFM) was introduced as an empirical model for forecasting catastrophic material failures related to natural hazards, such as landslides and volcanic eruptions, with mixed success. During the 2018 eruption of Kilauea volcano, Hawaii, the draining of the summit magma reservoir into the Lower East Rift Zone resulted in the formation of a new caldera at the summit. I tested the applicability of the FFM to caldera collapse by analyzing the cyclical earthquake swarms and ground deformation that occurred between 62 sudden major caldera collapse events. The progression of both the cumulative moment release of the cyclical earthquakes and the GNSS displacement show a major change in mid-June. In late May through early June, the progression of the parameters is consistent with strain localization or creep progression related to the development or activation of the ring fault system. From late June until the end of the eruption, parameter progression is roughly steady with initial accelerating increases in cumulative moment and displacement that shift to approximately linear progression. Analysis of repeating earthquake families in the cyclical swarms showed that the behavior of the repeaters was consistent with that of the cyclical swarms as a whole and suggested that each family undergoes its own progression of activation to termination. While the FFM analysis identified the system change in mid-June, it did not demonstrate an ability to forecast collapse events or the end of the eruption.

Ore-controlling structures of the Xiangshan volcanic Basin, SE China: Revealed from three-dimensional inversion of Magnetotelluric data

We report a high-resolution three-dimensional (3D) Magnetotelluric (MT) study to define the mineralizing system of the Xiangshan (XS) volcanic Basin, which hosts the largest volcanic-related uranium deposits in China. MT data from 81 stations were collected and inverted, using a 3D Truncated Newton (TRN) inversion algorithm. The generated electrical resistivity model reveals a high resistivity layer in the shallow, followed by a conductivity layer, and they were formed respectively by the Cretaceous Ehuling Formation and Daguding Formation. Under these Cretaceous formations, a series of high resistivity features delineate the Precambrian metamorphic basement. The contact zone between the high resistivity and conductivity layer corresponds to the inter-formational surface in the Cretaceous volcanic cover, whereas the contact zone between the volcanic cover and metamorphic basement represents the unconformity surface which was supported by gravity data. The identified faults in the 3D resistivity model coincide with the NE- and NS-trending faults observed on the surface. These faults are the crucial ore-controlling structures with high permeability allowing the ore-forming fluids to migrate upwards. We reveal a possible genetic model for the uranium mineralization in the XS volcanic Basin. The mixture of the descending meteoric water and ascending magmatic fluids along the deep faults formed the ore-forming fluids. The precipitation and enrichment of uranium were prone to occur in the ring faults, interfaces, unconformity surfaces and those geologic contacts intersecting with faults, where the physical and chemical properties of the ore-forming fluids were changed. Given that the mafic magmatism generally was coeval with the uranium mineralization, the deep-seated magmatism is supposed to be the force that drove the fluids upwards and governed the circulative convection of ore-forming fluids in the XS volcanic Basin.

Volcanic geological features and geochemical implications of Late Jurassic volcanoes in Duolun volcanic‐eruption basin of Inner Mongolia, China

Duolun volcanic‐eruption basin is part of the Mesozoic Tectono‐Magmatic Belt in the Great Khingan–Taihang Mountains. A lot of previous studies about this region have been made in geochronology, geomorphic genesis, magmatic origin, and Mesozoic Plate tectonic evolution. This article summarizes petrological features of volcanic rocks, lithofacies, volcanic sedimentary sequences, volcanic mechanism, and characters of volcanic eruptions in Duolun volcanic‐eruption basin. The volcanic sedimentary strata in this region are distributed along a series of NE and NNE tectonic belts, and accumulation thicknesses are controlled by volcanic edifices. We identified a total of seven volcanic edifices in Duolun volcanic‐eruption basin. For some typical volcanic edifices, we had studied their compositions, structures, geometries, and spatial distributions in detail, setting up regional volcanic tectonic framework. In the Manketouebo (J3m) cycle, the intensity of the eruption was large, characterized by large broken volcanoes in the early stage, and small dome and cone volcanoes in the late stage. In the Baiyingaolao (J3b) cycle, the strong volcanic activities manifested as Plinian‐type, are characterized by a large circular or nearly circular caldera at the top, moreover, late extrusive and intrusive domes in different cycles, ring faults and radial faults were also developed. Geochemical researches indicate that Duolun volcanic rocks have the basic characteristics of crust–mantle mixed source, and the tectonic environment for the Late Jurassic volcanic rocks is related to the collisional orogeny. Our work has great significance for further research on genesis of volcanic rocks, magma evolution, deep dynamics mechanism and their relationship between mineralization.

Crustal Strength Variations Inferred From Earthquake Stress Drop at Axial Seamount Surrounding the 2015 Eruption

AbstractVariations in stress drops of earthquakes associated with the April and May 2015 eruption of Axial Seamount, on the Juan de Fuca Ridge, suggest a reduction in crustal strength as a result of the eruption. Seismicity during the inflation and deflation periods was well recorded by ocean bottom seismometers located within and along the caldera. We use these nearby recordings and an empirical Green's function spectral ratio method to obtain corner frequencies for stress drops of earthquakes on caldera ring faults. We find stress drops from 0.6 to 43 MPa for 423 ring fault earthquakes (1.6 ≤ MW ≤ 3.6) and an average stress drop two times higher during the inflation period (6.4 MPa) prior to the eruption, than during the subsequent deflation (3.2 MPa). Stress drops also correlate with spatially varying shear wave speed, possibly reflecting a region of pervasive cracking in the northern caldera.

Caldera Collapse Geometry Revealed by Near‐Field GPS Displacements at Kīlauea Volcano in 2018

AbstractWe employ near‐field GPS data to determine the subsurface geometry of a collapsing caldera during the 2018 Kīlauea eruption. Collapse occurred in 62 discrete events, with “inflationary” deformation external to the collapse, similar to previous basaltic collapses. We take advantage of GPS data from the collapsing block and independent constraints on the magma chamber geometry from inversion of deflation prior to collapse onset. This provides an unparalleled opportunity to constrain the collapse geometry. Employing an axisymmetric finite element model, the co‐collapse displacements are best explained by piston‐like subsidence along a high angle (∼85°) normal ring fault that may steepen to vertical with depth. Reservoir magma has compressibility of 2→15 × 10−10 Pa−1, indicating bubble volume fractions from 1% to 7% (lower if fault steepens with depth). Magma pressure increases during collapses are 1 to 3 MPa, depending on compressibility. Depressurization of a triaxial point source in a homogeneous half‐space fits the data well but provides a biased representation of the source depth and process.

Active Normal Faulting, Diking, and Doming Above the Rapidly Inflating Laguna del Maule Volcanic Field, Chile, Imaged With CHIRP, Magnetic, and Focal Mechanism Data

AbstractThe Laguna del Maule volcanic field (LdMVF) in Chile, a rapidly inflating silicic volcanic system without historical eruption, is intersected by active regional faults. The LdMVF provides an opportunity to observe how faults influence, accommodate, or are driven by an actively deforming large silicic system. Here we use Compressed High Intensity Radar Pulse (CHIRP) acoustic reflection data to map the fault network in sediments captured within the eponymous lake at the LdMVF and combine our fault maps with the volcanic history, earthquake locations, focal mechanisms, and lacustrine magnetic data to interpret how faults and magmatism interact. Our seismic data image dominantly dip‐slip faults forming grabens within the lake, subparallel to regional faults. No indications exist in the seismic data to suggest that fault patterns were created by the volcanic system, either ring or radial faults. Fault strikes interpreted from seismic and magnetic data are consistent with mapped dike and fault orientations on land. We therefore interpret that active faults at the LdMVF are tectonic rather than volcanic in origin, forming a transtensional zone that hosts the magmatic system. However, vertical motion along a NS‐striking fault near the center of uplift suggests trapdoor‐style faulting above the volcanic center in which tectonic faults are reactivated to accommodate magmatic inflation and overlying deformation. Magnetic anomalies follow regional faults, suggesting that faults also provide migration pathways. Depositional patterns indicate a prior episode of uplift followed by quiescence, indicating that significant magmatically related uplift at the LdMVF can occur without an associated major eruption.

A Detection Method for Bearing Faults Using Complex-Valued Null Space Pursuit and 1.5-Dimensional Teager Energy Spectrum

Because of the nonlinear and unsteady characteristics of bearing vibration signals, the fault diagnosis of the rolling bearing in complex environments has become a challenging task. This paper deals with the bearing fault diagnosis method of vibration signals based on the complex-valued null space pursuit algorithm (NSP-CD) combined with the 1.5-dimensional Teager energy spectrum (1.5DTES). In the proposed algorithm, the bearing fault signals are decomposed by NSP-CD that is deduced by using partial differential equations and alternating direction method of multipliers, and several components that conform to the vibration signal mode are obtained. Then, the component containing the principal fault characteristic is selected according to the kurtosis value of each component. Finally, in order to accurately track the variation of amplitude and reduce noise interference, the 1.5DTES of the selected component is used to demonstrate the fault frequency of the bearing vibration signal. Experiments on vibration signals collected from electro-discharge machining with inner and outer ring faults demonstrate that the proposed method is more efficient and robust than other bearing diagnosis methods.

New insights into the stratigraphy and 230Th/U geochronology of the post-caldera explosive volcanism of La Primavera caldera, Mexico

La Primavera caldera is a Quaternary rhyolitic volcanic field located in the western part of the Trans-Mexican-Volcanic-Belt (TMVB). The caldera forming eruption of La Primavera occurred ~95 ka with the emplacement of the Tala ignimbrite. Here, we present a new stratigraphy and evolution of the post-caldera activity based on intense fieldwork, correlation of deposits, and ten 230Th/U geochronology dates in zircons. The collapse produced an 11-km wide caldera followed by the formation of an intra-caldera lake. After the caldera collapse, several rhyolitic domes were extruded, inside and outside the caldera ring-fault until 26.8 ka. The first post-caldera pyroclastic event took place 86.4 ka with the eruption that emplaced the Giant Pumice (GP) followed by the occurrence of at least fourteen pyroclastic units (UA to UN). The intra-caldera explosive activity came from the central resurgent Nejahuete composite dome with the deposition of the GP and A to D units between 86.4 and 71.5 ka. The extra-caldera explosive activity came from the San Miguel, Planillas and Tajo volcanic centers with the deposition of the E to N units inside the caldera and south of the caldera ring fault between 71.5 and 26.8 ka. Three eruptions were originated at San Miguel volcanic center between 71.5 and 60.3 ka (units E, G and H) and six eruptions dated between 68.9 and 44.7 ka were originated at Planillas volcanic center (units F, I, J, K, L and M). The last eruption of the caldera occurred between 44.7 and 26.8 ka at the Tajo volcanic center (UN). The eruptions appear as pyroclastic successions interbedded with lake deposits (units GP and A-B) and as subaerial deposits separated by paleosols or lahar deposits (units C-M). The revised stratigraphy indicates that the caldera resurgence occurred right after the caldera collapse 93.8 ka and continued until 75.8 ka. This new pyroclastic stratigraphy provides key information on the post-caldera evolution of La Primavera.

Structural analysis of syn-depositional hydrothermal veins of the 3.48 Ga Dresser Formation, Pilbara Craton, Australia

The lower chert unit of the 3.48 Ga Dresser Formation (Pilbara Craton, Western Australia) hosts Earth’s oldest convincing evidence of life in the form of stromatolites in a depositional setting that has been interpreted as either a shallow marine lagoon, an active volcanic caldera, or a basin deposited during regional extension.Understanding the environment where early life thrived is important not only for early life studies on Earth, but in the search for life on Mars, and for understanding the setting for the origin of life.Structural analysis of the extensive network of syn-depositional hydrothermal chert-barite veins that immediately underlies the Dresser was undertaken in order to test if deposition occurred within an evolving caldera system, or during regional extension.Over 190 hydrothermal veins were mapped for their geometry and relative age relationships.Bedding orientations were recorded within nine fault-bounded structural sub-blocks and used for back-rotating the measured veins to their original orientation.The results show that:1)There are four main vein systems, including three that were emplaced during deposition of the Dresser Formation lower chert unit, and a fourth that was emplaced within syn- to post-depositional listric growth faults;2)The majority of veins were sub-vertical prior to regional tilting;3)The first three vein systems show mutually cross-cutting relationships;4)Vein densities and the number of vein systems vary between sub-blocks;5)Conjugate vein networks (NE-SW and NW-SE) dominate two middle and northern sub-blocks.These results show that the first three vein systems were emplaced through fracturing under a stress regime with a vertical σ1. Vertical conjugate fractures are consistent with sandbox models of overburden fracturing during emplacement and discharge of a magma chamber in a volcanic caldera. Areas of single vein orientations reflect marginal areas of the caldera system, dominated by radial or by ring faults. The veins in late listric growth faults represent the final period of caldera collapse, which controlled the depositional thicknesses of overlying strata, possibly during subsequent regional extension.These results document an unique setting for earliest life on Earth, within shallow water and terrestrial deposits of an active, low-eruptive caldera setting.