Geological investigations planned for the Europa Clipper mission will examine the formation, evolution, and expression of geomorphic structures found on the surface. Understanding geologic features, ...their formation, and any recent activity are key inputs in constraining Europa’s potential for habitability. In addition to providing information about the moon’s habitability, the geologic study of Europa is compelling in and of itself. Here we provide a high-level, cross-instrument, and cross-discipline overview of the geologic investigations planned within the Europa Clipper mission. Europa’s fascinating collection of ice-focused geology provides an unparalleled opportunity to investigate the dynamics of icy shells, ice-ocean exchange processes, and global-scale tectonic and tidal stresses. We present an overview of what is currently known about the geology of Europa, from global to local scales, highlighting outstanding issues and open questions, and detailing how the Europa Clipper mission will address them. We describe the mission’s strategy for searching for and characterizing current activity in the form of possible active plumes, thermal anomalies, evidence for surface changes, and extremely fresh surface exposures. The complementary and synergistic nature of the data sets from the various instruments and their integration will be key to significantly advancing our understanding of Europa’s geology.
The Earth Magnetic Anomaly Grid at 2 arc min resolution version 3, EMAG2v3, combines marine and airborne trackline observations, satellite data, and magnetic observatory data to map the location, ...intensity, and extent of lithospheric magnetic anomalies. EMAG2v3 includes over 50 million new data points added to NCEI's Geophysical Database System (GEODAS) in recent years. The new grid relies only on observed data, and does not utilize a priori geologic structure or ocean‐age information. Comparing this grid to other global magnetic anomaly compilations (e.g., EMAG2 and WDMAM), we can see that the inclusion of a priori ocean‐age patterns forces an artificial linear pattern to the grid; the data‐only approach allows for greater complexity in representing the evolution along oceanic spreading ridges and continental margins. EMAG2v3 also makes use of the satellite‐derived lithospheric field model MF7 in order to accurately represent anomalies with wavelengths greater than 300 km and to create smooth grid merging boundaries. The heterogeneous distribution of errors in the observations used in compiling the EMAG2v3 was explored, and is reported in the final distributed grid. This grid is delivered at both 4 km continuous altitude above WGS84, as well as at sea level for all oceanic and coastal regions.
Plain Language Summary
Rocks and minerals have differing magnetic properties that can enhance or suppress the local magnetic field, whose primary source is the Earth's core. These fluctuations, called magnetic anomalies, can be up to 10% of the strength of the total field. Analysis and interpretation of magnetic anomalies is used in geodynamic, tectonic, and geological investigations, as well as in geophysical exploration; these anomalies can also significantly distort local compass and GPS headings. EMAG2v3 provides a global map of the location and strength of these anomalies that can be used to increase navigational accuracy and to study the structure and evolution of the Earth's lithosphere. It comes with a global map of uncertainties, reflecting heterogeneity in survey data quality.
Key Points
This grid combines marine, airborne, ground, and satellite observations to map magnetic anomalies arising from lithospheric sources
The grid was compiled using no a priori information about geologic structures or ages
It includes over 50 million new data points added to the Geophysical Database System (GEODAS) in recent years
Archean rock exposures in the Yangtze Craton of South China are scarce and have been only studied in small-scale outcrops for understanding its early crustal evolution. Geological investigations have ...been carried out for three Neoarchean gneissic granitic plutons from the Dabie orogen in the northeastern margin of the Yangtze Craton. Zircon U-Pb geochronology constrains the emplacement of high-K monzogranite at 2645±30 Ma, high-K syenogranite at 2630±37 Ma and Na-rich granodiorite at 2497±29 Ma. These findings provide direct evidence for the existence of ∼2.7–2.5 Ga rocks in the Dabie orogen, which significantly contribute to the distribution and evolution of Neoarchean basement rocks in the Yangtze Craton. Zircon crystals from the three granite samples give
ε
Hf
(
t
) values of −0.9 to 3.7, −4.2 to −0.4 and −4.7 to 0.1, respectively, corresponding to
T
DM2
ages of 3186–2909, 3372–3141 and 3297–3005 Ma. The magmatic zircons have
δ
18
O values of 5.06±0.27‰ to 5.79 ±0.30‰ (average 5.59‰), 6.14±0.24 to 7.35±0.26‰ (average 6.87‰) and 5.95±0.17‰ to 7.09±0.17‰ (average 6.55‰), respectively. Considering the possible decrease of
δ
18
O value due to the lead loss during post-crystallization alteration, the primary
δ
18
O values might be substantially higher than those of the normal mantle zircon value (
δ
18
O=5.3±0.6‰). These isotopic data indicate that the Jiamiao Neoarchean granites were largely generated through reworking of Paleo-Mesoarchean basement rocks with a minor contribution of supracrustal material. Integrating our findings with previous results, we infer that the Archean-Paleoproterozoic complexes/terranes of the Yangtze Craton have distinct petrogenesis and the timings of the transition from Na-rich to high-K granites, crustal growth, and tectonothermal evolution before ∼2.0 Ga. However, all of them underwent metamorphism at about 2.0 Ga. These observations also reveal that the Yangtze Craton might comprise several microcontinents that evolved individually and collided to form a unified craton at ∼2.0 Ga, synchronous with the assembly of the Columbia supercontinent. However, the lack of relevant data from the southeastern Yangtze Craton may have a critical influence on this conclusion and should be solved in the future.
Hydrogeological conditions within fracture zones control subsurface fluid, solute, and heat flux and storage. While conventional groundwater methods using induced disturbances often require elaborate ...and expensive equipment, passive methods that use observed responses of groundwater levels to atmospheric pressure and Earth tides provide the opportunity to estimate hydrogeologic properties without having to conduct field testing. We present estimates of hydraulic properties of a fault‐damage zone embedded within crystalline rock using responses to natural perturbations, and then compare these to estimates obtained using conventional methods. We calculate the skin factor using the exhaustive algorithm to improve the consistency between the tidal and conventional methods and compare it with different barometric‐response methods in the frequency and time domains. For the tidal method, the hydraulic conductivity is 16% larger than the estimate obtained from a conventional aquifer test, the barometric‐response method in the frequency domain is 6% larger, and the inverse, Hvorslev's, CBP, and Valois's methods in the time domain are, respectively, 71%, 72%, and 97% smaller and 624% larger. Estimated fault‐damage zone properties yield a hydraulic diffusivity of D ≈ 3 m2 s−1 and a permeability of k ≈ 4 × 10−13 m2 (0.4 Darcy), which confirms the presence of a highly damaged zone. The combined tidal‐ and barometric‐response methods provide a new and robust approach for understanding and characterizing hydrogeological properties of fault‐damage zones.
Plain Language Summary
Fault zones play key roles in hydrogeological flow and transport processes (e.g., fluid, solute, heat). Yet, obtaining hydraulic parameters using conventional methods (e.g., hydrogeological, structural‐geological investigations) in these systems remains challenging due to the cost and logistics involved. Alternatively, passive methods using groundwater‐level responses to natural forcing (e.g., barometric‐pressure variation, Earth tides) may be more practical, robust, and efficient. In this study, we evaluate multiple methods for estimating aquifer parameters in both the time and frequency domains, using data from a well‐aquifer system in the Xianshui River fault zone. We demonstrate that hydraulic parameters estimated by passive methods in the frequency domain are more similar to those estimated using conventional aquifer tests than time‐domain methods. We show that responses to natural forcing provide a reliable tool for evaluating hydraulic and hydrogeomechanical parameters in fracture‐zone areas and are especially helpful for monitoring the continuous evolution of fault damage‐zone permeability.
Key Points
Methods of water level in response to barometric pressure and earth tide were employed to determine the fault zone hydraulic properties
Both time‐ and frequency‐domain responses of the barometric pressure and tidal response method produced similar results with pumping test
The hydraulic diffusivity was around ∼3 m2 s‐1 which indicated the presence of a highly damaged zone in the study area
This paper presents a method for predicting karst features before and during tunnel construction. The prediction of karst consists of two components: an initial karst prediction using a fuzzy ...assessment system to evaluate the underground karst state and an updating karst prediction where appropriate geological investigation methods are selected based on the assessment of underground karst state. The investigation results are then used to update the underground karst state. The initial assessment system is based on a fuzzy comprehensive evaluation method. Nine influence factors are selected as the evaluation indices for the underground karst state, and each index is quantitatively rated to four grades. The membership of the evaluation index is determined by using a membership function, and the weights of these indices are distributed by using a fuzzy Analytical Hierarchy Process. The fuzzy transform principle and maximum membership degree principle are applied to determine the underground karst state level. Based on the assessment result, several techniques for geological investigation, including the seismic reflection method, ground penetrating radar, infrared water detection, transient electromagnetic method, and advance probe boreholes, are recommended to predict the location, size, and distribution of karst features ahead of tunnel faces. These geological investigations have different characteristics and can be combined to improve the accuracy of the geological prediction. The appropriate combination of investigation methods is selected using the assessed underground karst state, and the investigation results are also used as the input to update the underground karst state. The proposed method can improve the prediction of karst in tunnelling. An application of this method was performed in the Doupengshan tunnel project.
Mountains receive a greater proportion of precipitation than other environments, and thus make a disproportionate contribution to the world's water supply. The Luquillo Mountains receive the highest ...rainfall on the island of Puerto Rico and serve as a critical source of water to surrounding communities. The area's role as a long-term research site has generated numerous hydrological, ecological, and geological investigations that have been included in regional and global overviews that compare tropical forests to other ecosystems. Most of the forest- and watershed-wide estimates of precipitation (and evapotranspiration, as inferred by a water balance) have assumed that precipitation increases consistently with elevation. However, in this new analysis of all known current and historical rain gages in the region, we find that similar to other mountainous islands in the trade wind latitudes, leeward (western) watersheds in the Luquillo Mountains receive lower mean annual precipitation than windward (eastern) watersheds. Previous studies in the Luquillo Mountains have therefore overestimated precipitation in leeward watersheds by up to 40%. The Icacos watershed, however, despite being located at elevations 200-400 m below the tallest peaks and to the lee of the first major orographic barrier, receives some of the highest precipitation. Such lee-side enhancement has been observed in other island mountains of similar height and width, and may be caused by several mechanisms. Thus, the long-reported discrepancy of unrealistically low rates of evapotranspiration in the Icacos watershed is likely caused by previous underestimation of precipitation, perhaps by as much as 20%. Rainfall/runoff ratios in several previous studies suggested either runoff excess or runoff deficiency in Luquillo watersheds, but this analysis suggests that in fact they are similar to other tropical watersheds. Because the Luquillo Mountains often serve as a wet tropical archetype in global assessments of basic ecohydrological processes, these revised estimates are relevant to regional and global assessments of runoff efficiency, hydrologic effects of reforestation, geomorphic processes, and climate change.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The integration of inverse thermal history modeling of new geochronological data with structural analyses from the western flank of the Domuyo volcano (∼36°30′S) allows us to propose a detailed ...cooling history of a key region in the Southern Andes. The Domuyo area is located in the northwestern part of the Chos Malal fold‐and‐thrust belt in the back‐arc of the Southern Andes. Despite extensive geological investigations in this region, details about the early stages of Andean deformation remain poorly understood. The present study focuses on the interpretation and integration of new U‐Pb, fission track, and (U‐Th‐Sm)/He data constraining the Cretaceous to Paleogene exhumation history of the Southern Andes at these latitudes. The results indicate two main episodes of rapid cooling during Albian‐Campanian and Eocene times that can be related to exhumation driven by two main contractional pulses. The first event promoted basement cooling/exhumation associated with the uplift and erosion of a broad N‐S striking antiform; whereas the Eocene episode triggered the inversion of the preexisting N‐S striking Manchana Covunco normal fault and the deformation of the Mesozoic sedimentary cover. The two orogenic phases are separated by a potential period of orogenic quiescence during the Paleocene. These new insights highlight the importance of the initial compressional stages of mountain building in the Southern Andes at these latitudes.
Key Points
Thermal modeling reveals a stepwise history composed of two rapid cooling phases for Albian to Campanian and Eocene times
The first phase relates with the exhumation of the Paleozoic basement promoted by the uplift and erosion of a broad N‐S striking antiform
The second phase involves the inversion of the Manchana Covunco fault and the deformation of the Mesozoic sedimentary cover
The research includes work on historical buildings, fortifications and cult monuments. Because of its diverse architectural and historical heritages, Albania offers plenty of research opportunities ...particularly in the repair of the geotechnical structures. A set of geological and geotechnical conditions will be analysed in order to comprehend conditions of two case studies placed in Peqini region. These are of significant importance according to their construction and for the fact that their closed contour foundations are present from the Romans period (in the Peqini castle) and constructed with limestone material brought from an older object (in the Clock Tower). Combination of type of structure and plain terrain geological characteristics are assessed. The goal is to contribute in the geotechnical assessment and revitalization of the case studies selected as objects with value for the community and for the field of geotechnical maintenance. Ultimately, this fosters a better appreciation of the historical heritage in Albania through the understanding of their geotechnical predictions reliability.
This paper presents zircon U-Pb ages, whole-rock major and trace element data, and Hf isotope data for the metagabbros from the Zhushan pluton and gabbros from the Taiping pluton along the boundary ...area of Jiamusi and Songnen-Zhangguangcai Range massifs and adjacent regions, which will not only place important constraints on the rock-forming ages, source characteristics and tectonic setting of these gabbros, but will also provide insights into understanding the Permian tectonic evolution between the Jiamusi Massif and the Songnen-Zhangguangcai Range Massif. Zircon U-Pb dating, determined using laser ablation-inductively coupled plasma-mass spectrometry and secondary-ion mass spectrometry, indicates that the magmatic zircons from the Zhushan and Taiping plutons yield 206Pb/238U ages of 256±2Ma and 259±3Ma, respectively, interpreted as the emplacement ages of the intrusions. The metagabbros from the Zhushan pluton display the geochemical characteristics of calc-alkaline series rocks, and are enriched in light rare earth and large ion lithophile elements, and depleted in Nb, Ta, P, Zr and Hf. The εHf(t) values of magmatic zircons in these metagabbros vary from −5.47 to +0.74. All these geochemical features indicate that the primary magma of the Zhushan pluton was derived from an enriched lithospheric mantle source that was metasomatized by subducted slab-derived fluids. The gabbros from the Taiping pluton are also enriched in large ion lithophile elements (e.g., Rb, Ba and U) relative to high field strength elements, and have negative Nb-Ta-P anomalies, with εHf(t) values of −4.02 to −1.70. It is inferred that they also formed from a primary magma generated by the partial melting of enriched lithospheric mantle that was metasomatized by subducted slab-derived fluids. The rocks from the Zhushan and Taiping plutons have similar petrogenetic processes, but their primary magmas are likely to be derived from two distinct magma sources based on geochemical and isotopic compositions. According to zircon U-Pb ages, geochemical data, Hf isotope data and regional geological investigations, we conclude that the generation of the metagabbros in the Zhushan pluton was most likely related to westward subduction of the Mudanjiang oceanic plate beneath the Songnen-Zhangguangcai Range Massif, and the gabbros from the Taiping pluton were the result of eastward subduction of the Mudanjiang oceanic plate beneath the Jiamusi Massif. Hence, we suggest that the Jiamusi Massif and Songnen-Zhangguangcai Range Massif were not amalgamated before the Late Permian.
Display omitted
•Mafic intrusions along the boundary area of Jiamusi and Songnen-Zhangguangcai Range massifs were emplaced at 259–256 Ma.•Two mafic suites have similar petrogenetic processes, but their primary magmas are likely to be derived from two distinct magma sources.•The eastward- and westward-directed subduction of the Mudanjiang Ocean lithosphere is most likely mechanism for the formation of Permian rocks in the boundary area between the Jiamusi Massif and Songnen-Zhangguangcai Range Massif.
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