The distribution of magmatism and related endogenous metallogeny within short intervals of geological time displays strong lateral zonal pattern governed by the positions of contemporaneous eugeosynclines, i.e. previous oceanic basins. This pattern includes: (1) the eugeosyncline with ultramafics and mafics, and with Cu, Au, Cr, Pt; (2) the amagmatic back troughs filled by clastic sediments; (3) a zone of granite-granodiorite batholiths with Au, Mo; (4) a zone of diorite-monzonite with PbZn; (5) a zone of standard and LiF granites with Sn, W, Mo; and (6) a zone of alkaline plutons.The zones in (3)–(5) correspond to calc-alkaline volcanism, and the zone in (6) to alkaline volcanism. The zonal pattern is related to the activity along fossil Benioff zones. Great transversal faults displaced structural-magmatic and metallogenic zonality far inside continents. They are interpreted as transform faults. The existance of a zonal pattern is discussed in terms of plate tectonics. 相似文献
The paper is focused on the evolution of the Earth starting with the planetary accretion and differentiation of the primordial material (similar in composition to CI chondrites) into the core and mantle and the formation of the Moon as a result of the impact of the Earth with a smaller cosmic body. The features of the Hadean eon (ca. 4500–4000 Ma) are described in detail. Frequent meteorite-asteroid bombardments which the Earth experienced in the Hadean could have caused the generation of mafic/ultramafic primary magmas. These magmas also differentiated to produce some granitic magmas, from which zircons crystallized. The repeated meteorite bombardments destroyed the protocrust, which submerged into the mantle to remelt, leaving refractory zircons, indicators of the Early Earth’s geologic conditions, behind.The mantle convection that started in the Archean could possibly be responsible for the Earth’s subsequent endogenous evolution. Long-living deep-seated mantle plumes could have promoted the generation of basalt-komatiitic crust, which, thickening, could have submerged into the mantle as a result of sagduction, where it remelted. Partial melting of the thick crust, leaving eclogite as a residue, could have yielded tonalite-trondhjemite-granodiorite (TTG) melts. TTG rocks are believed to compose the Earth’s protocrust. Banded iron bodies, the only mineral deposits of that time, were produced in the oceans that covered the Earth.This environment, recognized as LID tectonics combined with plume tectonics, probably existed on the Earth prior to the transitional period, which was marked by a series of new geologic processes and led to a modern-style tectonics, involving plate tectonics and plume tectonics mechanisms, by 2 Ga. The transitional period was likely to be initiated at about 3.4 Ga, with the segregation of outer and inner cores, which terminated by 3.1 Ga. Other rocks series (calc-alkaline volcanic and intrusive) rather than TTGs were produced at that time. Beginning from 3.4-3.3 Ga, mineral deposits became more diverse; noble and siderophile metal occurrences were predominant among ore deposits. Carbonatites, hosting rare-metal mineralization, could have formed only by 2.0 Ga. From 3.1 to 2.7 Ga, there was a period of “small-plate” tectonics and first subduction and spreading processes, which resulted in the first supercontinent by 2.7 Ga. Its amalgamation indicates the start of superplume-supercontinent cycles.Between 2.7 and 2.0 Ga, the D″ layer formed at the core-mantle interface. It became a kind of thermal regulator for the ascending already tholeiitic mantle plume magmas. All deep-seated layers of the Earth and large low-velocity shear provinces, called mantle hot fields, partially melted enriched EM-I and EM-II mantles, and the depleted recent asthenosphere mantle, which is parental for midocean-ridge basalts, were finally generated by 2 Ga. Therefore, an interaction of all Earth’s layers began from that time. 相似文献
Doklady Earth Sciences - Novel data from mineralogical studies of the peridotite xenoliths from the Komsomol’skaya–Magnitnaya kimberlite pipe, Upper Muna field, Siberian craton, are... 相似文献
The first radiocarbon-dated pollen record from the Mamakan section is presented. This record has become the basis for the reconstruction of the vegetation and climate of the Middle Holocene in the Mamakan archaeological area, where a number of well-known Siberian archaeological sites of the Late Mesolithic–Middle Bronze period are located. Reconstructions suggest that sparse spruce and larch stands dominated in the area between 6450 and 6150 cal BP. Later, from 6150 to 4700 cal BP, Scots pine began to spread in a warmer climate than before, following the general trend of its expansion in the southern part of Eastern Siberia. A cooler climate than previously with increased soil and air humidity occurred in the Mamakan region from 4700 to 3840 cal BP, causing the regional expansion of Siberian pine. The time interval from 3840 to 3600 cal BP was characterized by the significant development of pine, spruce, and larch forests. On the basis of the age model, we assume that, in the lower reaches of the Vitim River and, probably, in other mountain regions north of Lake Baikal, Scots pine spread about 600 years later than in the Cis-Baikal region and east of the lake. This transition from dark coniferous-taiga to light coniferous-taiga with a predomination of Scots pine signifies the most fundamental change in vegetation of the Baikal region in the Holocene. This is often discussed as one of the possible causes of the Middle Neolithic cultural hiatus (6660–6060 cal BP), which has been documented in the archaeological records from different parts of this vast region. Reconstruction of vegetation in the Mamakan region suggests that the territory of the Nizhnii Vitim River has been favorable for humans during most of the hiatus recorded in the Cis-Baikal area and may have been considered as a refuge for populations of hunter-gatherers in the Middle Neolithic.
The comparative analysis of the Earth’s surface deformations measured by ground-based and satellite geodetic methods on the regional and zonal measurement scales is carried out. The displacement velocities and strain rates are compared in the active regions such as Turkmenian–Iranian zone of interaction of the Arabian and Eurasian lithospheric plates and the Kamchatka segment of the subduction of the Pacific Plate beneath the Okotsk Plate. The comparison yields a paradoxical result. With the qualitatively identical kinematics of the motion, the quantitative characteristics of the displacement velocities and rates of strain revealed by the observations using the global navigational satellite system (GNSS) are by 1–2 orders of magnitude higher than those estimated by the more accurate methods of ground-based geodesy. For resolving the revealed paradoxes, it is required to set up special studies on the joint analysis of ground-based and satellite geodetic data from the combined observation sites. 相似文献
Izvestiya, Physics of the Solid Earth - Empirical data obtained by studying the Earth’s surface deformations in the fault zones induced by exogenous, endogenous, and manmade processes are... 相似文献
Izvestiya, Atmospheric and Oceanic Physics - The aim of this work is to analyze the results of geodeformation monitoring at the Korchagin oil, gas, and condensate deposit in the Caspian Sea. The... 相似文献