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Global Geology
2019 Vol.22 Issue.2
Published 2019-06-25
Articles
Articles
67
Geochemistry and zircon U-Pb chronology of quartz porphyry in Yuejinshan Fe-polymetallic deposit of Heilongjiang
JIN Ye, CUI Bo, WANG Li, YANG Baihui, YIN Yue, LI Qing, WANG Shuo, CHEN Xiaohang, LIU Xiang
Quartz porphyry in Yuejinshan Fe-polymetallic deposit is one of the rock masses, which formed the granite belt relating to the late Yanshanian skarn-type Fe-polymetallic deposits in the eastern Heilongjiang, and is also closely related to the metallogenic space of the Fe-polymetallic deposits. Quartz porphyry has the zircon U-Pb concordia age of 125.0±1.1 Ma, overall showing high Si (SiO
2
=74.48%-75.00%), rich alkaline (Na
2
O+K
2
O=7.93%-8.17%, K
2
O/Na
2
O=1.39-1.46), and poor Mg (MgO=0.27%-0.31%), with the A/CNK value being 0.95-0.99, having the characteristics of obvious enrichment of LREE and medium Eu negative anomaly (0.69-0.74), indicating that the rock belongs to quasi-aluminous high potassium calc-alkaline series and has the same characteristics as those of the I-type granite. The rock is also characterized by the enrichment of LILE and active incompatible elements, and depletion of HFSE such as Nb, Ta, P and Ti, with the Mg
#
value being 32-37, indicating that the rock originated from partial melting of crustal materials. It can be concluded from the above characteristics or data and from the distribution of contemporary magmatic rocks in the area, that quartz porphyry in Yuejinshan Fe-polymetallic deposit was formed in a tectonic background of the subduction of the paleo-Pacific plate in late Yanshanian.
2019 Vol. 22 (2): 67-77 [
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78
Zircon U-Pb geochronology, geochemistry and petrogenesis of syenogranite from Angeer Yinwula area in Inner Mongolia
LIU Hanlun, WANG Keyong, LI Jian, CAI Wenyan, TANG Wenhao, WANG Changhong
The study presents the results of U-Pb dating of zircons and whole-rock geochemical analyses of syenogranite in Angeer Yinwula area, China, with the aim of determining its formation time, petrogenesis and regional setting. Zircon U-Pb data obtained by LA-ICP-MS indicate that the syenogranite formed in the Early Cretaceous (136.1±0.9 Ma). Geochemically, the rock is characterized by high SiO
2
(76.63%-77.58%) and Na
2
O+K
2
O (8.00%-8.32%), low MgO (0.02%-0.04%) and TFe
2
O
3
(0.51%-0.84%), and is enriched in LREEs and LILEs, depleted in HREEs and HFSEs. It belongs to high-K calc-alkaline, metaluminous-weakly peraluminous, exhibiting an affinity to I-type granite. All these characteristics implied that the syenogranite in this region derived from crust-mantle mixed source. Overall, the regional geology, geochronology and geochemical features suggest that the formation of the syenogranite was related to the subduction of the Paleo-Pacific Ocean.
2019 Vol. 22 (2): 78-90 [
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91
Application of shallow high-resolution transient electromagnetic method (TEM) in geological investigation of debris flow
LIU Chenyang, ZHANG Xiaopei, DU Lizhi, WANG Yong
In the investigation of debris flow, the detection of the source area of the post-disaster debris flow is an important basis for evaluating the distribution of the debris flow accumulation layer and the subsequent control. In this paper, a shallow high-resolution TEM is used to detect the debris flow source area in Dashigou village, Yongji County, Jilin Province. The purpose of this investigation is to determine the depth range of debris flow damage. The detection results show that there is an obvious low resistance zone at about 10 m depth along the survey line, which is in good agreement with the drilling data and the high density electrical detection. It is proved that the depth is the maximum impact depth of the debris flow. The practical engineering proves that the method has high resolution in shallow layer detection, high efficiency and convenience in field acquisition. The maximum detection depth range of this method is 30-40 m, which meets the requirements of high efficiency and accurate detection for regional debris flow source area, and has high practical application value.
2019 Vol. 22 (2): 91-97 [
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239
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98
Assessing applicability of Near-Infrared/Green/Blue UAV modified camera in crop monitoring: a case study of eastern Zimbabwe
MUREFU Mike, CHEN Shengbo
Unmanned Aerial Vehicles (UAVs) have become popular and their use in agriculture monitoring is attracting more and more attention. There has emerged another class of agricultural UAVs whose normal consumer grade Red/Green/Blue (RBG) bands cameras have been modified to include the Near-Infrared (NIR) band by replacing one of the visible channel bands. This reduces the cost for agricultural UAVs. However, few researches have assessed the suitability of these modified UAV cameras in agricultural remote sensing. This study employed a modified UAV consumer grade camera with Blue/Green/Near Infra-red (BGNIR) bands to assess its applicability in crop remote sensing monitoring. Two experimental fields in Eastern Zimbabwe were used to assess the applicability of the modified BGNIR UAV camera in potato stress detection, maize senescence monitoring and chlorophyll concentration variations in bananas. Processed Green Normalized Vegetation Index (GNDVI) maps from the UAV imagery were compared with actual ground data of geo-tagged images taken during the UAV flights. Visual comparison between the ground and UAV imagery showed positive correlation. Highly stressed potato plants had lower GNDVI values than the healthier looking plants. Matured maize canopies also had lower GNDVI values than the late mature plants whose leaves were still green. GNDVI values in bananas from the first flight ranged from 0.094 91 to 0.334 74 and after the application of Nitrogen/Phosphorous/Potassium (NPK) fertilizer the GNDVI values ranged from 0.124 61 to 0.555 64. Increase in nitrogen also increases chlorophyll concentration in plant leaves hence the values of GNDVI increase after fertilization. We conclude that consumer grade modified UAV cameras are suitable in remote sensing of agricultural crops. Their adoption and utilization reduce the cost burden on farmers in developing countries especially in Africa, and help them to monitor their crops more efficiently.
2019 Vol. 22 (2): 98-104 [
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105
Research and application on CSAMT constraint inversion
HE Rongqin, YU Qingshui, LI Jing, SONG Erqiao
In this paper, according to the method of electrical constraint inversion, we can improve the accuracy of inversion interpretation using the constraint of electrical logging data in the inversion process, which is conducive to obtain more abundant geoelectric information. On the basis of the conventional OCCAM inversion algorithm, the model roughness in the objective function is improved, and the formula of the electrical constraint inversion iterative algorithm is derived in detail based on the modified objective function. Taking the geothermal exploration in Changbai Mountain area as an example, the measured CSAMT data are used as the resistivity model for inversion, and the electrical property is constrained by the actual data from wells drilled in the section. It can be found that the method of electrical constraint inversion can improve the accuracy of inversion interpretation and guide the development of constrained inversion methods in different ways.
2019 Vol. 22 (2): 105-111 [
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190
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112
3D numerical simulation in acoustic-elastic coupled media with staggered-grid finite-difference method
PENG Changhua, WANG Deli, ZHOU Jinju
Acoustic-elastic coupled media is often encountered in most marine explorations, and accurate simulation of acoustic-elastic coupled media is of great significance. At present, the study of acoustic-elastic coupled media still assumes that the solid of the acoustic-elastic coupled media is isotropic, but this assumption is not in accordance with the actual situation. In this paper, we derive the solid media of acoustic-elastic coupled media from isotropic media to anisotropic media, and propose an acoustic-elastic coupled medium based ontransverse isotropic media with vertical symmetric axes (VTI) to improve the accuracy of forward modeling. Based on the relationship between the Thomsen parameter and the coefficient matrix of the anisotropic elastic wave equation, we transform the Thomson parameter into a velocity model with anisotropic properties. We use a staggered grid finite difference method to simulate the propagation of a wavefield in a three-dimensional acoustic-elastic coupled media. We obtain the snapshots of the wave field when the solid of the acoustic-elastic coupled media is an isotropic medium and a VTI media. When the solid of the acoustic-elastic coupled media is considered VTI media, we can observe the qP wave and qS wave that cannot be observed in the isotropic medium from the wave field snapshot. We can also find that the seismic records obtained by the method we use are more realistic. The algorithm proposed in this paper is of great significance for high-precision ocean numerical simulation.
2019 Vol. 22 (2): 112-120 [
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121
Site selection and data processing of GNSS receiver calibration networks based on TEQC and GAMIT
ZHOU Changjie, MAO Jiuchang, WANG Hongyao, WU Qiong
This study introduces the site selection and data processing of GNSS receiver calibration networks. According to the design requirements and relevant specifications, the authors investigate the observation conditions of the potential sites and collect the experimental GNSS observation data. TEQC is used to evaluate the data availability rate and multipath effects of the observation data to determine the appropriate site. After the construction and measurement of the calibration network, the baseline processing of the medium and long baseline network is conducted by GAMIT. The accuracy indexes including NRMS, difference between repeated baselines, and closure of independent observation loops all meet the specified criteria.
2019 Vol. 22 (2): 121-127 [
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128
Monte Carlo simulation of scintillation crystal detector for formation element logging
HAN Ruiyi, WANG Zhuwen
Formation elements logging is a neutron gamma spectroscopy logging technique used to acquire the content of elements and minerals by recording the gamma ray produced by the reaction of neutron and elemental nucleus in the formation. It has a wide usage in discriminating complex lithology and evaluating unconventional reservoir. The Monte Carlo simulation model of formation elements logging tool is established in this paper, with which the effects of tool parameters including the material and length of the scintillation crystal and source spacing on logging responses are modeled. The results show that the energy response of LaBr
3
:Ce crystal is better than others, and the detection efficiency increases with the crystal length but decrease with source spacing. The above results may be used as a reference for optimizing the tool structure design.
2019 Vol. 22 (2): 128-132 [
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133
Applications of gravity data in identification of faults and tectonic boundaries of a working area in Inner Mongolia
ZOU Bolun, LI Tonglin, WU Yangang, WU Heyu, SHI Jiaqiang, LIN Baoze
In order to determine the tectonic framework of the Late Paleozoic sedimentary basin of the studied area in Inner Mongolia, horizontal derivative, vertical derivative, total gradient modulus, tilt angle, and Euler deconvolution methods were used to process the high-precision gravity data. Four major faults and six secondary faults have been identified according to the horizontal fault position information provided by the first four methods, and the fault depth information were obtained using the Euler deconvolution method. The interpreted faults were identified as the main basin-controlling structures in the study area, which was helpful for deepening the understanding of the basin's structure, as well as providing important references for delineating hidden polymetallic ore veins.
2019 Vol. 22 (2): 133-140 [
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