Kai‐Xing Wang  Hui Huang  Xiao‐Dong Liu  Jia‐Yong Pan 《Geological Journal》2019,54(1):39-61

The Late Mesozoic Pucheng granitic complex in northern Fujian Province is composed of the Chengbu and Shipi peralkaline A‐type granitoids, the Pucheng A‐type granitoid, and the Yongxing I‐type granitoid. The Chengbu and Shipi peralkaline granitoids were dated at 160 and 130 Ma, respectively, and are explained by the melting of meta‐igneous rocks with T_DM² of 1.70 Ga and 2.01 to 2.05 Ga. The Pucheng A‐type granitoid was emplaced at 110 and 102 Ma and is divided into two groups. Group 1 comprises the extremely felsic A‐type granite (SiO₂ > 73 wt.%), high FeO^T/MgO (>16), and low Ga/Al ratios and Zr + Nb + Ce + Y content. Group 2 contains a less‐evolved A‐type granite with high Zr + Nb + Ce + Y content. Both groups can be explained by dehydration melting of meta‐igneous rocks at low pressure. The diversity between the two groups was caused by different physicochemical environments. The Yongxing I‐type granite, which is abundant in mafic microgranular enclaves, was emplaced at 106 ± 1 Ma. It can be explained by the mingling of mantle‐derived and crustal‐derived magmas. Our data along with previously published data demonstrate that the northern Fujian Province was under an extensional environment from 160 to 100 Ma. This was caused by the NW‐trending subduction of the palaeo‐Pacific Plate. The Jurassic peralkaline granitoids were probably generated in a rift environment as a result of the reactivation of pre‐existing faults caused by the initial subduction of the palaeo‐Pacific Plate. The Early Cretaceous peralkaline granitoids may represent a rift environment as a tectonic response from low‐angle subduction to an increasing subduction dip angle. The 100 Ma granitoids derive from an intraplate extensional environment caused by the roll‐back of the palaeo‐Pacific Plate.  相似文献   

    

Yun‐peng He  Jing‐gui Sun  Zhong‐yu Wang 《Geological Journal》2019,54(6):3786-3802

The Huangshandong deposit, located in the Central Asian Orogenic Belt (CAOB), is the largest Ni–Cu sulfide deposit in the eastern Tianshan and Beishan regions of China. The deposit is hosted in a postorogenic intrusion that comprises diorite, gabbrodiorite, bojite, olivine gabbro, gabbronorite, troctolite, and lherzolite. Here, we report the Permian zircon U–Pb crystallization ages of 278.5 ± 2.1 Ma, 278.1 ± 1.9 Ma, and 279.6 ± 1.9 Ma for the olivine gabbro, bojite, and gabbrodiorite, respectively, as well as geological, petrological, and geochemical data for the various lithofacies of the deposit. As a result of the edge cooling effect, the intrusion cooled rapidly from the outside inwards as follows: crystallizing diorite → gabbrodiorite → gabbro → lherzolite → gabbronorite. In addition, further tectonic activity resulted in the injection of a more primitive magma in place, which crystallized the lherzolite in the bottom and middle transitional zones of the intrusion. The crystallization sequence of the intrusion is generally as follows: olivine → orthopyroxene + labradorite → clinopyroxene + labradorite → amphibole + andesine. At the beginning of mineral crystallization, the metalliferous magma was segregated due to sulfide immiscibility and separated by gravity. With gabbronorite crystallization, the immiscible liquid sank to the base of the magma chamber and crystallized as Cu‐ and Ni‐rich sulfides. Tholeiitic and calc‐alkaline rocks are characterized by relative enrichment in large‐ion lithophile elements and depletion in high‐field‐strength elements, and values of Th/Ta (2.25–5.94), (Nb/La)_N (1.88–4.39), and Th/Nb (0.29–0.82) indicate that the mantle source was composed of a dehydrated subducted plate or mantle wedge. In addition, values of Nb/U (2.64–10.68) and Ce/Pb (1.33–3.53) suggest that the magma was contaminated by the continental crust during its ascent along pre‐existing structures in the Carboniferous strata.  相似文献   

    

Zong‐Yuan Tang  De‐You Sun  An‐Qi Mao  Dong‐Guang Yang  Chang‐Zhou Deng 《Geological Journal》2019,54(6):3737-3754

In this paper, we report on LA‐ICP‐MS zircon U–Pb dates of 14 Mesozoic volcanic rocks from the central Great Xing'an Range (CGXR). These data are integrated with the temporal and spatial distribution of local magmatism‐related Mesozoic mineralization, in an effort to develop an understanding of the geodynamic evolution of the region. Periodic magmatic events in the GXR date from ~1,703 through ~145 Ma. Mesozoic volcanism in the CGXR can be subdivided into three episodes: Triassic (250–205 Ma), Early–Middle Jurassic (182–165 Ma), and Late Jurassic–Early Cretaceous (155–115 Ma). A revision of the previously defined volcanic sequence is offered using a combination of our zircon U–Pb ages and published Mesozoic geological and geophysical evidence from northeast China. We propose that (a) Early–Middle Triassic volcanism in the CGXR resulted from subduction of the Paleo‐Asian oceanic plate; (b) Late Triassic volcanism was related to subduction of the Mongol–Okhotsk oceanic plate (especially near the Erguna Block) and subsequent extension after the closure of the Paleo‐Asian Ocean; (c) Early–Middle Jurassic volcanism was mainly controlled by the southward subduction of the Mongol–Okhotsk oceanic plate; (d) Late Jurassic–initial Early Cretaceous magmatism was initiated by closure of the Mongol–Okhotsk Ocean; and (e) late Early Cretaceous volcanism was induced following the final closure of the Mongol–Okhotsk Ocean and rollback of the Paleo‐Pacific oceanic plate.  相似文献   

    

Jusun Woo  Young‐Hwan S. Kim  Sung Kwun Chough 《Geological Journal》2019,54(4):1993-2015

Microbial carbonate has been increasingly recognized as an important player for sediment production and building up of organosedimentary deposits. The integrated spatio‐temporal pattern of microbial facies is important for understanding carbonate production processes in a carbonate platform. This paper focuses on the sedimentary facies and development of a microbe‐dominated platform in the Cambrian North China Platform (the Zhangxia Formation of the Cambrian Series 3) in Shandong Province, China. In the entire Zhangxia platform, deposition started with oolite‐dominated shoal‐lagoon system with rare microbialites. The shoal‐lagoon system in the western part of the study area kept up with sea‐level rise and formed a flat‐topped platform, whereas that in the eastern part failed to keep up and thus drowned. The platform top then changed to a microbe‐dominated carbonate platform consisting of thrombolite, stromatolite, dendrolite, and Epiphyton framestone. The initial significant microbialites were biohermal thrombolite and dendrolites, which subsequently changed into wider biostromal forms. The morphologic change was largely due to initial rapid rise in sea level and the following deceleration. Extensive biostromes of laterally coalesced thrombolite–Epiphyton bioherms occur in the shale‐dominated eastern part. These microbialites then perished by platform‐wide drowning. The vast initial development of microbialite facies of the Zhangxia Formation in the Shandong area was important for the establishment of an extensive microbialite‐dominated carbonate factory made by combination of an absence of reef‐building metazoans and possible transition of seawater chemistry from aragonite sea to calcite sea in the Cambrian Series 3. It is comparable to the other carbonate environments lacking dominant metazoan reef builders after the mass extinctions.  相似文献   

    

Sojen Joy  Sarbani Patranabis‐Deb  Dilip Saha  Hielke Jelsma  Roland Maas  Ulf Sderlund  Sebastian Tappe  Gert van der Linde  Amlan Banerjee  Unni Krishnan 《Geological Journal》2019,54(5):3170-3173

We thank Patil Pillai et al. for preparing a critique on our article (Joy et al., 2018). Patil Pillai et al. contest the analytical procedure utilized for the carbonates and “geological information” documented in our research article and raise concerns on our conclusions. We hereby provide our reply to each of their comments.  相似文献   

    

X.‐J. Wu  Y.‐F. Yuan 《Astronomische Nachrichten》2019,340(1-3):121-125

The two stars of stellar binaries can be tidally disrupted by supermassive black holes (SMBHs) or supermassive black hole binaries (SMBHBs) in sequence. In this contribution, we review our recent study about double tidal disruption events (DTDEs) with SMBHBs. With the help of scattering experiments, we find that the time interval between two successive tidal disruption events (TDEs) depend on the semimajor axis of incident stellar binaries. For stellar binaries with 1 M_⊙ for each companion star and a semimajor axis less than 100 au, the maximum time interval is about 150 days when the stellar binary is tidally disrupted by an SMBH. However, for an SMBHB, the time intervals can be very large, and the maximum can exceed 10,000 years. Moreover, we also compare the probabilities of a DTDE with the time interval larger than 150 days by the SMBHB and of two separate TDEs by the SMBH with the same time interval. We find that, for the time interval of 150 days to 15 years, the probability of DTDEs by the SMBHB with a large mass ratio (i.e., q_bhb ≳ 0.1 ) is larger than that of the SMBH scenario. Finally, according to our results, we suggest that DTDEs with the time interval of 150 days to 15 years could be useful tools for finding SMBHB candidates with the mass ratio q_bhb ≳ 0.1 at galactic centers.  相似文献   

    

Michal Zaja ek  B. Czerny  Mary Loli Martínez‐Aldama  Vladimir Karas 《Astronomische Nachrichten》2019,340(7):577-585

By applying different statistically robust methods, we analyze the time lag between the continuum and ionized line‐emission (Mg II line) light curves for the distant bright quasar CTS C30.10 (redshift z∼0.9 ). The data were obtained by the 10‐meter South African Large Telescope (SALT) telescope in South Africa. In detail, we demonstrate the application of several methods using the interpolated cross‐correlation function (ICCF), discrete correlation function (DCF), z‐transformed discrete correlation function (zDCF), von Neumann estimator, and the JAVELIN code package. In particular, we discuss the uncertainties of these methods. In conclusion, we find that the quasar lies on the broad‐line region (BLR) size—monochromatic luminosity power‐law scaling, , which was already confirmed for low‐redshift sources. In case, the BLR size–luminosity relation holds for other distant sources, quasars could be used to probe cosmological models as “standard candles” complementary to supernovae Ia.  相似文献   

    

C.‐P. Hu  C.‐Y. Ng 《Astronomische Nachrichten》2019,340(4):340-345

Magnetars are strongly magnetized pulsars and they occasionally show violent radiative outbursts. They also often exhibit glitches that are sudden changes in the spin frequency. It was found that some glitches were associated with outbursts but their connection remains unclear. We present a systematic study to identify possible correlations between them. We find that the glitch size of magnetars likely shows a bimodal distribution, different from the distribution of the Vela‐like recurrent glitches but consistent with the high‐end of that of normal pulsars. A glitch is likely a necessary condition for an outburst but not a sufficient condition because only 30% of glitches were associated with outbursts. In the outburst cases, the glitches tend to induce larger frequency changes compared to those unassociated ones. We argue that a larger glitch is more likely to trigger the outburst mechanism, either by reconfiguration of the magnetosphere or deformation of the crust. A more frequent and deeper monitoring of magnetars is necessary for further investigation of their connection.  相似文献   

    

G. Piccinelli  J. Jaber‐Urquiza  A. Snchez 《Astronomische Nachrichten》2019,340(1-3):230-233

The effect of a homogeneous weak magnetic field on the decay process of a neutral scalar particle to a pair of charged fermions is studied. The decay rate is calculated through the imaginary part of the self‐energy of the scalar particle interacting with the charged fermions, at one loop. The weak field approximation can be performed in different ways, depending on the hierarchy of scales. Here, we explore the regime where the progenitor particle has a high transverse momentum and we find that the process is favored by the increase of the magnetic field. We compare our results with recent findings for a different kinematical regime and briefly discuss the possible physical reasons for the different behaviors. The phenomenon can be relevant in early universe events or in high‐energy collisions.  相似文献   

    

Zhi‐Fu Gao  Fang‐Kun Peng  Na Wang 《Astronomische Nachrichten》2019,340(9-10):1023-1029

Here, we summarize our recent work on the evolution of magnetic field and spin‐down of young pulsars including high‐B pulsars and magnetars. Our work includes the following three parts: (a) Based on the estimated ages of their potentially associated supernova remnants (SNRs), we estimate the values of the mean braking indices of eight magnetars with SNRs and find that five magnetars have smaller mean braking indices of 1 < n < 3, and we interpret them within a combination of magnetodipole radiation and wind‐aided braking. (b) The low braking index of n = 0.9(2) for PSR J1734‐3333 could undergo a supercritical accretion soon after its formation in a supernova explosion. The buried multipole magnetic fields will merge into a dipole magnetic field. Retaining the current field growth index ϵ = 1.34, this pulsar will become a magnetar with dB_p∼6.2(2) × 10¹⁴ G and dB_p∼1.06(4) × 10¹⁵ G after 50 kyrs and 100 kys, respectively. (c) By introducing a mean rotation energy conversion coefficient and combining the pulsar's high‐energy and timing observations with a reliable nuclear equation of state, we estimate the initial spin period, initial dipole magnetic field, and true age of PSR J1640‐4631. For this source, its measured high braking index n = 3.15(3) is attributed to a long‐term dipole magnetic field decay, and its soft X‐ray emission is attributed to anisotropic heating.  相似文献