RECOGNITION OF A 600-KM-LONG LATE TRIASSIC RARE METAL (Li-Rb-Be-Nb-Ta) PEGMATITE BELT IN THE WESTERN KUNLUN OROGENIC BELT, WESTERN CHINA

The rising demand of strategic metals, especially lithium, necessitates discovery of new resources to meet the global supply chain. Recently, several pegmatite-hosted rare metal (Li-Rb-Be-Nb-Ta) deposits have been discovered in the Western Kunlun orogenic belt, making it a new world-class rare metal resource (estimated ~7 Mt Li2O and 0.16 Mt BeO). Understanding the metallogenesis of this belt is critical to further evaluate the rare metal potential. In this study, columbite-tantalite (coltan) and monazite from rare metal pegmatites and zircon from potential parental granites were collected from five representative rare metal pegmatite deposits in the western, middle, and eastern parts of the Western Kunlun orogenic belt for U-Pb geochronology. The results indicate that despite the distances of the sampling localities in different parts of the Western Kunlun orogenic belt, the ages of pegmatite-hosted rare metal mineralization fall in a narrow range of ca. 208–204 Ma. These rare metal pegmatites are temporally and spatially related to adjacent postorogenic granites emplaced following the closure of the Paleo-Tethys Ocean. The compositional characteristics of K-feldspar, biotite, and muscovite of the granites and pegmatites, along with regional mineralogical and textural zonation of the pegmatites, suggest that the rare metal pegmatites were derived from the volumetrically much more important, highly fractionated granitic intrusions. We propose that, in combination with the data from previous studies, the 218–204 Ma interval represents a newly recognized rare metal metallogenic period linked with granitic intrusions in the Western Kunlun orogenic belt, revealing a 600-km-long late Triassic rare metal pegmatite belt composed of multiple ore fields formed in a similar metallogenic setting. These results emphasize the importance of identifying fertile, Late Triassic to Early Jurassic granitic intrusions for rare metal pegmatite exploration. Furthermore, combined with recent studies on the Songpan-Ganzi rare metal pegmatite belt along the eastern segment of the Paleo-Tethys, this study further highlights the great potential of rare metal resources in this global tectonic zone.

New Detrital Apatite Fission Track Thermochronological Constraints on the Meso-Cenozoic Tectono-Thermal Evolution of the Micangshan-Dabashan Tectonic Belt, Central China

The Micangshan-Dabashan tectonic belt, located in the southern Qinling-Dabie Orogen near the northeastern Tibetan Plateau, is a crucial area for understanding the processes and mechanisms of orogenesis. Previous studies have been focused on the cooling process via thermochronology and the mechanism and process of basement uplift have been investigated. However, the coupling process of basement exhumation and sedimentary cap cooling is unclear. The tectono-thermal history constrained by the detrital apatite fission track (AFT) results could provide valuable information for understanding crustal evolution and the coupling process. In this study, we provided new detrital AFT thermochronology results from the Micangshan-Dabashan tectonic belt and obtained nine high-quality tectono-thermal models revealing the Meso-Cenozoic cooling histories. The AFT ages and lengths suggest that the cooling events in the Micangshan area were gradual from north (N) to south (S) and different uplift occurred on both sides of Micangshan massif. The cooling in Dabashan tectonic zone was gradual from northeast (NS) to southwest (SW). The thermal histories show that a relatively rapid cooling since ca. 160 Ma occurred in the Micangshan-Dabashan tectonic belt, which was a response to the event of Qinling orogenic belt entered the intracontinental orogenic deformation. This cooling event may relate to the northeastward dextral compression of the Yangtze Block. The sedimentary cap of Cambriano-Ordovician strata responded positively to this rapid cooling event and entered the PAZ since ca. 63 Ma. The deep buried samples may be limited affected by climate and water erosion and the accelerated cooling was not obvious in the Late Cenozoic. Collectively, the cooling processes of basement and sedimentary cap in Micangshan-Dabashan tectonic belt were inconsistent. The uplift of the sedimentary area is not completely consistent with that of the basement under thrust and nappe action. The rigid basement was not always continuous and rapidly uplifted or mainly showed as lateral migration in a certain stage because of the different intensities and modes of thrust and nappe action, and the plastic sedimentary strata rapidly uplifted due to intense folding deformation.

Integrated geological interpretation of remote sensing data (Boysun structural-tectonic zone)

In recent years, remote sensing data are increasingly used in the practice of oil and gas prospecting. This article discusses the main methodological aspects of identifying oil and gas promising structures by using materials for interpreting remote sensing data and a complex of geological and geophysical data. Remotely sensed data exhibit a regional review of the various geological formations and tectonic fracture zone and faults that are otherwise not possible detection by human eyes on the ground. The method of structural interpretation space image allows you to: detail the internal structure of oil and gas regions; to reveal the position and features of the tectonic blocks, structures of the second and third (anticlines, synclines, monoclines, etc.) orders; identify major disruptive violations; identify chains of local structures; fix the transverse structural elements that determine tectonic fragmentation. By deciphering the remote sensing data, the distribution and nature of the lineament network marking disjunctive dislocations and zones of increased fracturing are revealed and analyzed, as well as ring structures are detected, which in most cases indicate local structures of the sedimentary cover at different depth sections. The lithology and lineament interpreted from these multi-level data were integrated with data collected from the ground.

Gravity Anomalies And Crustal Structure Of The Eastern Part Of The Verkhoyansk Fold-And-Thrust Belt, NE Russia: Evidence From The Junction Area Of The Adycha-Elga And Allakh-Yun Tectonic Zones

The results of geophysical studies of the junction area of the Adycha-Elga and Allakh-Yun tectonic zones of the Verkhoyansk fold-and-thrust belt located on the submerged eastern margin of the Siberian craton are presented. Three structural-mineral complexes are recognized: Archean-Paleoproterozoic, Mesoproterozoic-Middle Carboniferous, and Upper Carboniferous-Early Mesozoic. The Early Jurassic plume-related basaltic volcanism and suprasubduction Late Jurassic-Early Cretaceous granitoids, regional Brungadin and Suntar faults are identified. The goal of the research is to identify deep heterogeneities and clarify the structure of the Earth’s crust in the junction area of the Adycha-Elga and Allakh-Yun tectonic zones of the Verkhoyansk fold-and-thrust belt. The analysis of gravitational anomalies is carried out, their transformations are performed – distinguishing the medium and low-frequency components, the vertical derivative Vzz, and calculating the equivalent distribution of sources of density masses at depth. It is determined that the hidden granitoids of the Adycha-Elga tectonic zone are located mainly in linear zones of decompaction at a depth of about 3.5 km. In the Allakh-Yun zone, a large gravitational minimum has been identified, where it is assumed that there is a magma granitoid chamber occurring at a depth of about 9 km. The model of the deep structure of the territory is based on the analysis of materials on the reference seismic profile 3-DV with the use of gravimetric data and the regional structure of the territory. According to the results of the wave pattern interpretation, the thickness of the lithosphere varies from 41 to 44 km. The thickness of the Upper Carboniferous-Triassic terrigenous rocks is 8-12 km, Mesoproterozoic - Middle Carboniferous carbonate-terrigenous complex is up to 12 km. The Archean-Paleoproterozoic crystalline basement occurs at a depth of 19-21 km. The Conrad discontinuity is assumed at a depth of about 30 km. Intense deformations of the crystalline basement are recognized, and trans-crust faults are identified.

Study of Radioactivity in Bajaur Norite Exposed in the Himalayan Tectonic Zone of Northern Pakistan

Radioactivity in Granites of Pakistan systematically increases from south to north. The Ambella Granite found at the northern edge of Pakistan is highly radioactive. Radioactivity measurements made on, so called, Bajaur Granite, located in northern Pakistan, have been found to be lowest among all the granitic rock of the area. In order to find out the exact nature of Bajaur rocks, mineralogical studies were carried on rock chips and powdered samples. The Bajaur Norite contains plagioclase feldspar more than 45% as the chief constituent. Orthopyroxene and clinopyroxene are 27% and 18%. Quartz, biotite, and some opaque minerals are also found in accessory amounts. Bajaur Granite is in fact not a granite but Norite, which is rich in Na-Ca plagioclase series of feldspars. The plagioclase feldspar rich in Na-Ca are low in radioactivity. Moreover, the average gamma activities of 226Ra, 232Th, and 40K (4.98 ± 0.13 Bqkg−1, 4.03 ± 0.31 Bqkg−1, 204.40 ± 4.72 Bqkg−1 and a total of all three radionuclides are 214.00 ± 5.39 Bqkg−1) for Bajaur Norites are found too be much less than the average of the world’s Granites. Indoor and outdoor hazard indices of Bajaur Norite are much below building materials used throughout the world and largely beneath their criterion restrictions. As per radiations’ hazards are concerned, the Bajaur Norite as a building stone may be considered as the safest material available in the area that does not pose any radiological hazard.

Reconstruction of Tsunami Occurrence on Okushiri Island, Southwestern Hokkaido, Japan

The eastern margin of the Japan Sea is located along an active convergent boundary between the North American and Eurasian tectonic plates. Okushiri Island, which is situated off the southwest coast of Hokkaido, is located in an active tectonic zone where many active submarine faults are distributed. Studying the records of past tsunamis on Okushiri Island is important for reconstructing the history and frequency of fault activity in this region, as well as the history of tsunamis in the northern part of the eastern margin of the Japan Sea. Five tsunami deposit horizons have been identified previously on Okushiri Island, including that of the 1741 tsunami, which are interbedded in the coastal lowlands and Holocene terraces. However, these known tsunami deposits date back only ~3,000 years. A much longer record of tsunami occurrence is required to consider the frequency of submarine fault activity. In this study, we cored from 7 to 25 m depth in the Wasabiyachi lowland on the southern part of Okushiri Island, where previous studies have confirmed the presence of multiple tsunami deposits on peat layer surfaces. The results indicate that the Wasabiyachi lowland comprises an area that was obstructed by coastal barriers between the lowland and the coast at ~8.5 ka and consists of muddy sediment and peat layers formed in lagoons and floodplains, respectively. In addition, event deposits and 15 tsunami horizons were observed among the turbidites and peat layers, dating back as far as 3,000 years. Combined with previous findings, Okushiri Island has sustained 20 tsunami events between ~7.5 ka and the present. These findings are critical for investigating the activities of submarine faults off the southwestern coast of Hokkaido, as well as for determining tsunami risks along the coast of the Japan Sea between North Tohoku and Hokkaido.

Peak Ground Acceleration (PGA) and Peak Ground Velocity (PGV) Analyze for Microzonation of Earthquake Hazard Area: Case Study in West Nusa Tenggara

The Lombok region is located around a complex tectonic zone with an Indo-Australian oceanic crust transition zone with Australian continental crust in the west and Sundanese arc in the east. This complexity makes some area in West Nusa Tenggara have a high level of earthquake vulnerability and to determine the potential level of seismic damage risk this study was conducted by analyzing Peak Ground Acceleration (PGA) and Peak Ground Velocity (PGV) using earthquake data since 2000 - March 2020 with an intensity more than M4.5. Earthquake data are analyzed using the Yin-Min Yu formula to get the relationship between Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), and earthquake intensity, so areas with risk level of earthquake damage can be mapped as preliminary earthquake mitigation schemes. The results of the study show that the highest PGA value in West Nusa Tenggara is 74.73 gal at the bedrock and when it on the surface, the PGA value can increase due to amplification of local soil conditions. Likewise PGV value about 32.21 gal where this maximum value is located in East Lombok Regency and North Lombok Regency. According to the classification of PGA and PGV values, the study area has a potential high-risk level of earthquake damage.

Pyritic deposits of North Caucasus. Prospects of minerality of Hudes deposit

Актуальность работы заключается в изучении и обосновании перспектив выявления новых рудных тел в слабо изученных частях рудного поля. Рассмотрены геологические особенности крупного Худесского медноколчеданного месторождения Северного Кавказа. Рудные залежи месторождения разведаны и локализованы только в восточной части рудного поля. Центральная часть и западный фланг поля практически не разведаны, хотя здесь сохраняется полный рудоносный разрез и выделена мощная Северная зона пиритизированных метасоматитов. Месторождение планируется Уральской горнорудной компанией в ближайшие годы ввести в промышленную разработку (ведется разработка технического проекта). Целью проведенных исследований являлось составление схемы разреза продуктивной части девонской вулканической постройки со стратиграфическими уровнями рудных залежей гидротермально-осадочных руд и установление прямых признаков скрытого оруденения. Методы работы. В процессе проведения полевых работ выполнено подробное описание этих крупнообломочных плотных пород, состоящих из обломков глыб вулканитов и кластогенно-гидротермального мелкообломочного цемента с редкими (1%) обломками массивных колчеданных руд и пиритизированных метасоматитов. Результатом работ явилось обоснование в качестве главного поискового признака наличия обломков массивных руд в секущих телах эксплозивных брекчий, указывающих на скрытое промышленное оруденение. Доказывается поствулканический характер этих рудоносных эксплозивных брекчий. Рекомендуется направление поисковых работ. Поисковые буровые скважины при прослеживании и выявлении стратиграфических рудных уровней нужно располагать по субмеридиональным профилям. В существующей штольне №19 следует пройти в северном направлении разведочные квершлаги с учётом секущего вертикального положения поствулканических тел эксплозивных брекчий. Учитывая связь нижнепермского вулканизма с золотоносным Северным разломом Тырныауз-Пшекишской тектонической зоны, близость и геологическое единство Чучкурского и Худесского месторождений, следует провести опробование эксплозивных брекчий на комплекс полиметаллов, включая золото. The relevance of the work is to study and substantiate the prospects for identifying new ore bodies in poorly studied parts of the ore field. The geological features of the large Khudessky copper-crusted deposit of the North Caucasus are considered. The ore deposits of the deposit have been explored and localized only in the eastern part of the ore field. The central part and the western flank of the field are practically not explored, although a complete ore-bearing section is preserved here and a powerful Northern zone of pyritizedmetasomatites is identified. The deposit is planned to be put into commercial development by the Ural Mining Company in the coming years (a technical project is being developed). The aim of the researchwas to draw up a section diagram of the productive part of the Devonian volcanic structure with stratigraphic levels of ore deposits of hydrothermal-sedimentary ores and to establish direct signs of hidden mineralization. Methods. In the course of field work, a detailed description of these large-block dense rocks consisting of fragments of blocks of volcanites and clastogenic-hydrothermal small-block cement with rare (1%) fragments of massive pyrite ores and pyritizedmetasomatites was performed. The results of the work were the substantiation as the main search sign of the presence of fragments of massive ores in the secant bodies of explosive breccias, indicating hidden industrial mineralization. The post-volcanic character of these ore-bearing explosive brecciasis proved. The direction of search operations isrecommended. Prospecting drilling wells should be located along submeridional profiles when tracing and identifying stratigraphic ore levels. In the existing tunnel No. 19, it is necessary to pass exploration quershlags in the northern direction, taking into account the secant vertical position of the post-volcanic bodies of explosive breccias. Taking into account the connection of the Lower Permian volcanism with the gold-bearing Northern fault of the Tyrnyauz-Przekish tectonic zone, the proximity and geological unity of the Chuchkur and Khudessky deposits, it is necessary to test explosive breccias for a complex of polymetals, including gold.

A new formation model of the Atlantic-Arctic heterochronous rifting system: A concept and basic provisions

A new formation model of the global Atlantic-Arctic heterochronous rifting system is substantiated, according to which the Central and North Atlantics, Labrador-Baffin seas, and Arctic Ocean represent morpho-tectonic elements of different orders of the united recent Atlantic-Arctic Ocean. Evolution of the global rift system of this ocean includes three stages: the first stage (D–J1) was expressed by establishment of a tectonic zone in the lithosphere of Pangea with formation of the ophiolite ultrabasite-gabbro association; the second stage (J1–₽1) represented stretching of the continental crust to form depressions and uplifts with areal manifestation of trap magmatism of Cretaceous and other ages; and the third one (₽2–present) is neotectonic-magmatic reactivation with formation of a middle ridge, that is being accompanied by outpouring of glassy basalts and by hydrothermal manifestations. Within the framework of this model, the history of formation is reconstructed of the Eurasian Basin and the Gakkel Ridge, that were included in the Russia's updated application for expansion of the outer continental shelf border.

Himalayan Tectonic Belt: Morlet Wavelet Variation and Seismic Harmony

Morlet wavelet analysis is a method of studying the periodic spectrum of non-stationary physical signals and is applied to the Himalayan Tectonic Belt to explore whether there is any seismic periodicity, and to explore the possibility of harmony or commonality of properties among the seismic activities of different zones. The earthquake sequence during 1951–2016 with magnitudes M ≥ 6.0 is analysed. Wavelet non-periodicity for the Centre zone suggests a non-uniform spatial–temporal distribution of earthquake movement between plates which may relate with the rare great earthquakes, while the periodicities for the west and east zones may suggest the concurrence with the adjustment of the tectonic movement of the east- and west-end regions of the Himalayan Tectonic Belt relative to its central core. These three zones collectively form the Himalayan Tectonic Belt. This contains a periodicity of about five years of seismic activity that tests successfully with a 95% confidence statistic. Borrowing from the concept of musical harmony, this is the significant seismic harmonic which reflects the Belt’s pervasive tectonic stress and an overall harmony of continent–continent plate convergence. Morlet wavelet analysis also reveals the Himalayan Tectonic Belt and the Pamir–Hindu Kush Tectonic Zone to be engaged as a big new family: the Himalayan Tectonic Belt Plus. It is demonstrated that this new whole also has seismic harmony with the common property again being the 5-year periodicity. This indicates a unified structure of pervading active stress and seismic harmony permeating the overall seismicity.