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Global Geology
2021 Vol.24 Issue.3
Published 2021-08-25
129
U － Pb －Hf isotopes and petrogenesis of Late Jurassic akakitic quartz monzodiorite in Xingcheng area，western Liaoning Province
YAN Xiangyu，YANG Debin,MU Maosong and HAO Leran
The petrogenesis and geodynamic setting of the Late Jurassic Baita porphyry quartz monzodiorite in Xingcheng--Liaoxi area provide information for understanding the Mesozoic tectonic evolution of the northeastern North China Craton． In this paper，geochronological，whole-rock geochemical，and in-situ zircon Hf isotopic analyses of Baita porphyry quartz monzodiorite were investigated to constrain the crystallization age and petrogenesis．Zircons exhibit typical oscillatory zoning in cathodoluminescence images and show relatively high Th /Uratios ( 0． 78--1． 62) ，and U-Pb analyses indicate that these rocks were crystallized during the Late Jurassic( 159 ± 1 Ma) ． Geochemically，they are characterized by high contents of SiO2 ( 65． 21wt%--65． 31wt%) ，Al2O3( 16． 29wt%--16． 31wt%) ，Sr ( 521 ×10 －6 －539 ×10 －6 ) ，and Sr /Y ratio ( 45． 1--47． 8) but low Y ( 10． 9 ×10 － 6 － 12． 0 × 10 － 6 ) ，with obvious adakitic geochemical affinities． These above-mentioned findings，combined with their negative εHf( t) values ( － 21． 7 to － 20． 2) ，corresponding two-stage model age ( TDM2) of 2 579--2 484 Ma，as well as low MgO ( 1． 38wt%--1． 39wt%) ，Cr ( 18． 5 ×10 －6 －19． 5 × 10 －6 ) and Ni ( 9． 45 × 10 －6 －9． 46 × 10 － 6 ) values，indicate that Baita porphyry quartz monzodiorite may be generated by partial melting of the Neoarchean-Paleoproterozoic thickened basaltic lower crust． Based on the results from this study and previous regional studies，it is concluded that Baita porphyry quartz monzodiorite was spatially related to the westward subduction of the Paleo-Pacific plate．
2021 Vol. 24 (3): 129-143 [
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Characteristics and sources of ore － forming fluids of South Narimalahei copper polymetallic deposit in East Kunlun，Qinghai
SUN Qu，WANG Li，ZHANG Yongsheng，FAN Xingzhu，ZHANG Guofeng，SHENG Jianhua，CHEN Xiaohang and LIU Xiang
The South Narimalahei area is located on the north side of the Middle Kunlun fault in the eastern section of the East Kunlun composite orogenic belt． The ore body is veined and controlled by structures and secondary fissures，which occurs in the structural alteration fracture zone in the Late Triassic granodiorite． In this deposit，copper mineralization is closely related to silicification and sericification． The formation process of the deposit includes hydrothermal mineralization and supergene oxidation． In this paper，the fluid inclusion mineralogy，microscopic temperature measurement and stable isotope studies have been carried out for ore of the main mineralization stage． The results show that the primary gas-liquid two-phase inclusions and a small amount of single-liquid inclusions are mainly developed in the quartz in the main mineralization stage． The results of microscopic temperature measurement show that the ore-forming fluid which has low temperature ( 151． 7℃-- 205． 8℃) ，low salinity( 2． 06wt%--4． 94wt% NaCl) ，low density ( 0． 86--0． 92 g /cm3 ) and shallow formation( 1． 5--3． 0 km) is a hydrothermal solution of NaCl-H2O system． Hydrogen and oxygen isotope results show that the ore-forming fluids mainly come from atmospheric precipitation，with a small amount of magmatic fluids participating．It is preliminarily determined that the South Narimalahei copper polymetallic deposit is a lowtemperature hydrothermal vein deposit．
2021 Vol. 24 (3): 144-153 [
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154
Structural characteristics and hydrocarbon accumulation in Bashituo area，Tarim Basin
GUO Yiru，YU Minghui，LI Zongyu，BAYAN Xianmutihan，JIA Yudong and WANG Xinyu
According to well logs，core，seismic and other geological data，the authors studied the tectonic evolution stages，trap formation stages，fault and fracture development in the Bashituo area，and furthermore，analyzed the time of hydrocarbon accumulation，hydrocarbon migration pathways and related controversial issues in the study area． It is believed that the tectonic evolution in the study area can be divided into three stages，namely Late Hercynian，the Early Himalayan and the Late Himalayan． In the Late Hercynian，tectonic movement led to folding and faulting，resulting in the embryonic form of anticlinal traps． In the Early Himalayan，affected by both tectonic movement and transformation，deep faults reactivated and cut through the Lower Tertiary strata． After the Early Himalayan tectonic movement，faulting stopped and no vertical migration pathway was available． Then hydrocarbon migrated laterally along the sand bodies in the Bachu Formation and accumulated in the Carboniferous reservoirs． However，the Carboniferous accumulation was formed late，and the tectonic movement was weak at the Late Himalayan，and faults were underdeveloped，so the reservoirs in the deep Bachu Formation were not disturbed．
2021 Vol. 24 (3): 154-159 [
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Application of topography fast marching method in landslide
YANG Junjie，SUN Hui,WEI Chengwu，JIANG Zhenghong and LI Meng
Geophysical exploration methods are important tools for landslide disaster assessment，landslide
treatment scheme design，and landslide prevention engineering． Seismic exploration，as an important geophysical exploration method，plays an critical role in geological disaster evaluation． Traveltime is one of the most frequently used seismic attributes． Among many different traveltime calculation methods，the fast marching method ( FMM) is featured for its advantages in high efficiency，high accuracy and strong stability． In this paper，the velocity models are established according to the real landslide models，and then the topography FMM is applied to these landslide models． The calculation results show that topography FMM outperforms in calculating the
traveltime for landslides．
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2021 Vol. 24 (3): 160-168 [
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Subsurface target recognition in Utopia Planitia of
Mars by Tianwen － 1 FP － SPＲ simulation
WANG Ying，FENG Xuan,LIANG Wenjing，LI Xiaotian and XUE Cewen
As a cold and dry planet，Mars contains water resources in the form of water ice，so that the electromagnetic waves can be transmitted to the deep underground to get the information of the topography and subsurface geological structure． Subsurface penetrating radar ( SPＲ) can be widely used in deep space exploration for a long time because of its non-destructive detection mode and its working characteristics not limited by visible light． It is an important type of equipment for detecting the subsurface structure of planets． Orbiter radar is mainly used in Mars exploration． However，because of its low resolution，it is difficult to describe the near surface structure，so there is a lack of radar data which can reflect the shallow information． In this paper，a threedimensional near surface model of Utopia Planitia on Mars is established． In order to make the simulation results more reasonable，the key factors such as topographic relief，subsurface rocks and water ice，and the variation of
dielectric constant in different layers are taken into account． Then the full polarization forward modeling is carried out by using the three-dimensional finite-difference time-domain method． The acquired full polarimetric subsurface penetrating radar ( FP-SPＲ) data with noise is preprocessed and further processed by Pauli decomposition．The underground reflection can be picked up more clearly from the Pauli decomposition results． This work is helpful to identify more details of subsurface structures and provides a reference for the measured data in
the future．
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2021 Vol. 24 (3): 169-176 [
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A voxel － based fine － scale 3D landscape pattern analysis using laser scanner point clouds
SUN Hongzhan and WU Qiong
The landscape pattern metrics can quantitatively describe the characteristics of landscape pattern and are widely used in various fields of landscape ecology． Due to the lack of vertical information，2D landscape metrics cannot delineate the vertical characteristics of landscape pattern． Based on the point clouds，a highresolution voxel model and several voxel-based 3D landscape metrics were constructed in this study and 3D metrics calculation results were compared with that of 2D metrics． The results showed that certain quantifying difference exists between 2D and 3D landscape metrics． For landscapes with different components and spatial configurations，significant difference was disclosed between 2D and 3D landscape metrics． 3D metrics can better
reflect the real spatial structure characteristics of the landscape than 2D metrics．
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2021 Vol. 24 (3): 177-182 [
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Super － resolution reconstruction based on CNN: A case study of Jilin － 1 multispectral data
JIN Daoming and WU Qiong
MS or MS + PAN is usually applied separately in convolutional neural network ( CNN) resolution reconstruction to obtain high-resolution MS images，but the difference between the two datasets is rarely studied．This paper introduced a dual-channel network and took MS and MS + PAN of Jilin-1 spectrum satellites as two
datasets to evaluate the performance of CNN resolution reconstruction，and analyzed the difference with bicubic and GS methods． The result of CNN reconstruction shows that MS + PAN dataset performed better than MS，
with about 6% improvement in spatial and spectral components，and the overall quality of MS + PAN dataset was slightly higher than that of MS dataset，with QNＲ from 0． 955 9 to 0． 958 4． The bicubic performed best in spectral components with the quality value of 0． 017，and GS performed best in spatial components with the quality values of 0． 044 3． CNN showed similar performance in spectral and spatial components with the two traditional methods and achieved the best overall quality with QNＲ value of 0． 958 4．
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2021 Vol. 24 (3): 183-188 [
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