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Global Geology
2019 Vol.22 Issue.1
Published 2019-03-25
Articles
Articles
1
A new member of Sphenopsida,
Neolobatannularia
gen.nov.from Late Triassic of western Liaoning, China
WANG Junyou, LI Tao, LIU Zhiping, GUO Bin, KANG Ai, NA Yuling, LI Yunfeng, WANG Hongshan, BO Junchen, SUN Chunlin
A new genus
Neolobatannularia
Sun et Li gen.nov.with the type species
Neolobatannularia liaonin-gensis
Sun et Li sp.nov.from the Upper Triassic Yangcaogou Formation of Beipiao,Liaoning,China,is de-scribed in this paper.The new taxon is attributed to Equisetales of Sphenopsida based on its branch with inter-nodes,node and leaves borne in whorls on nodes.It is a new member of the Mesozoic Sphenopsida.Although the new taxon shares some morphological characters with the genus
Lobatannularia
Kawasaki,a genus widely distributed in the Permian Cathaysia flora in East Asia,and the genus
Lobatannulariopsis
Yang from the Late Triassic of southwestern China,its unique branching pattern is markedly distinguished from the two known gene-ra.Some Triassic known species of
Lobatannularia
may belong to the present new genus
Neolobatannularia
.
2019 Vol. 22 (1): 1-8 [
Abstract
] (
421
) [
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1156KB] (
450
)
9
Ore mineral characteristics and zircon U-Pb geochronology of Yuanjiacun iron deposit in Shanxi
TONG Yuepeng, PENG Xiaolei, LIU Guoqing, YUE Liping, MA Dongmei
In order to further understand the ore characteristics and metallogenic age of Yuanjiacun iron deposit in Shanxi,the mineral composition characteristics of iron ore were studied on the basis of field investigation and microscopic observation.Magnetite,hematite,goethite and pyrite of different stages were identified according to their texture and structure features.Two sets of
207
Pb/
206
Pb ages have been obtained by ICPMS isotope dating of magnetite quartzite,of which the zircon age with metamorphic origin is 1 916 ±88 Ma,representing the main metamorphic age of iron deposit.Another group of magmatic zircons with rhythmic zones are of 2 280 ±30 Ma age,representing the diagenetic age of iron formation.In addition,scattered age records after metamorphism in-dicate frequent hydrothermal events after mineralization.Based on the mineral fabric characteristics and the age data of zircons of different origins,it is known that the deposit has undergone sedimentary mineralization peri-od,metamorphic mineralization period,hydrothermal mineralization period and weathering mineralization peri-od.
2019 Vol. 22 (1): 9-20 [
Abstract
] (
271
) [
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1KB] [
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1846KB] (
744
)
21
Carbonate pore type characterization using a statistical inversion method
LI Bonan
For carbonate reservoirs,vertical pore type heterogeneity records regional depositional history.How-ever,from the geophysics point of view,these microscopic characteristics cannot be described with conventional data-driven approaches.The author presents an upscale rock physics model which includes both modeling and inverting schemes in this study.According to the statistical comparability between lab measurements and well logs,the main idea is to study and utilize inherent statistical features in naturally occurred carbonate rocks.Firstly,using the critical porosity model as rock physical theory,relationships are built between pore structures and elastic responses.Furthermore,in logging data scale,key parameters are estimated through a statistical method,and thus pore types are classified.The methodology is successfully applied in the well YS1.It is be-lieved that this method will be a promising tool on handing pore complexity and inversion uncertainty in carbon-ate reservoir exploration.
2019 Vol. 22 (1): 21-28 [
Abstract
] (
188
) [
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1159KB] (
373
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29
Influences of coarse grid selection on Kirchhoff beam migration
LI Jiabin, SUN Hui, ZHANG Zhihou, HAN Fuxing, LIU Minchen
Kirchhoff beam migration is a beam migration method,which focuses on rapid imaging of geological structures.Although this imaging method ignores the amplitude information in the calculation process,it can calculate multi-arrival traveltime.This migration method takes into account both imaging accuracy and computa-tional efficiency.Kirchhoff beam migration employs coarse grid techniques in several key steps such as travel-time calculation,weight function calculation,and imaging calculation.The selection of the coarse mesh size has an important influence on the computational efficiency and imaging accuracy of the migration imaging meth-od.This paper will analyze this influence and illustrate the analysis results by the Marmousi data sets.
2019 Vol. 22 (1): 29-35 [
Abstract
] (
267
) [
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1051KB] (
385
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36
Zircon U-Pb chronology,geochemistry and Lu-Hf isotope constraints on genesis of monzonitic granite from Harizha area in eastern section of East Kunlun region
LI Qing, CUI Bo, WANG Li, PENG Bo, ZHANG Yong, JIN Ye, YIN Yue
The Harizha area is located in the eastern section of East Kunlun orogenic belt.The petrology,the zircon LA-ICP-MS U-Pb chronology and the petrogeochemistry of the monzonitic granite in the area were stud-ied.The results show that the formation age of the monzonitic granite in the Harizha area is 237.4 ±1.4 Ma,which belongs to Middle Triassic.The content of SiO
2
in the rock is 61.29%—63.30%,(K
2
O+Na
2
O) is 5.41%—5.84%,Al
2
O
3
is 14.80%—15.99%,the Mg
#
value is 46.33—48.33,and the aluminum saturation in-dex A/CNK is 0.87—0.91.Therefore,it can be concluded that the rock belongs to the I-type granite of quasi-aluminous high potassium Ca-alkaline series.The total REE content of the rock is 118.82×10
-6
—164.54×10
-6
,and the La/Yb ratios range from 7.77 to 10.13.Meanwhile,the rock does not show obvious Eu anoma-lies (δEu=0.61—0.75) and is characterized by enrichment of LREE and LILE such as Rb and K,relative de-pletion of HREE and HFSE such as Nb,Ti and Ta.Zircon Hf isotopic dating exhibits that the average
ε
Hf
(
t
) is -2.4 and the average of two-stage model age (t
DM2
) is 1 417 Ma,indicating that the source rocks are mainly crustal materials.It can be concluded from research findings and regional geological structural analysis that the monzonitic granite in the Harizha area originated from partial melting of the Mesoproterozoic mafic lower crust in the later stage of the subduction of the Paleo-Tethys Ocean.
2019 Vol. 22 (1): 36-49 [
Abstract
] (
351
) [
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1534KB] (
416
)
50
Miocene stratigraphic characteristics of Semliki basin in Albertine Graben
YANG Xipu, GE Zhunzeng, LIU Jun, CHEN Han
For the purpose of reservoir characterization of oilfields discovered in Albertine Graben,it is neces-sary to study the regional stratigraphy and sedimentary characteristics.The Semliki outcrops display a complete stratigraphy of Miocene,and the sediments are likely to provide valuable analogues for the reservoirs at Alber-tine Graben oilfields.The outcrops were observed and described in detail,mainly including lithology,colour,thickness,grain size and sedimentary structure.The sedimentology,depositional environment,climate,reser-voir geometries and dimensions were analyzed.The Miocene stratigraphic section of Semliki basin was finally es-tablished,with lithology,sedimentary structure,sedimentary cycle,interpretation and climate information on it.It provides an analogy for the reservoir characterization,especially provides a basis for appropriate prediction of reservoir geometries in the field.
2019 Vol. 22 (1): 50-55 [
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236
) [
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1387KB] (
471
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56
Experimental study on mechanical properties of granite under different cooling methods after thermal treatment
ZHOU Junhong, WANG Xin, HU Zhongjun, XU Rongboyu, YANG Dong, TU Zhenyu
Static uniaxial compression tests were conducted on 16 granite specimens after thermal treatment using a heating device and an electro-hydraulic servo pressure-testing machine.The effects of air cooling and water cooling on the physical and mechanical properties of the high-temperature granite specimens were studied.Test results showed that the longitudinal wave velocities of the high-temperature specimens gradually decreased after they were cooled by water and air.The peak stress and elastic modulus of the samples decreased gradually with an increase in temperature,whereas their peak strain increased gradually.The effects of peak stress and peak strain were considerably more evident when cooling by water than by air.This result demonstrated that the thermal cracking of the granite specimens,and consequently,their internal micro-fractures,further developed when the specimens were cooled by water.
2019 Vol. 22 (1): 56-61 [
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258
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567KB] (
381
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62
Study of denoising method for nonhyperbolic prestack seismic reflection data
GOU Fuyan, LIU Yang, ZHANG Peng
Removing random noise in seismic data is a key step in seismic data processing.A failed denoising may introduce many artifacts,and lead to the failure of final processing results.Seislet transform is a wavelet-like transform that analyzes seismic data following variable slopes of seismic events.The local slope is the key of seismic data.An earlier work used traditional normal moveout (NMO) equation to construct velocity-dependent (VD) seislet transform,which only adapt to hyperbolic condition.In this work,we use shifted hyperbola NMO equation to obtain more accurate slopes in nonhyperbolic situation.Self-adaptive threshold method was used to remove random noise while preserving useful signal.The synthetic and field data tests demonstrate that this method is more suitable for noise attenuation.
2019 Vol. 22 (1): 62-66 [
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] (
237
) [
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696KB] (
384
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