The 7 ka old Qixiangzhan lava flow(QXZ,Tianchi volcano)represents the last eruptive event before the 946 CE,caldera-forming‘Millennium’eruption(ME).Petrographic,whole rock,mineral composition,Sr-Nd isotopic data on ...The 7 ka old Qixiangzhan lava flow(QXZ,Tianchi volcano)represents the last eruptive event before the 946 CE,caldera-forming‘Millennium’eruption(ME).Petrographic,whole rock,mineral composition,Sr-Nd isotopic data on QXZ show that:(a)the lava consists of two components,constituted by comenditic obsidian fragments immersed in a continuous,aphanitic component;(b)both components have the same geochemical and isotopic variations of the ME magma.The QXZ and ME comendites result from fractional crystallization and crustal assimilation processes.The temperature of the QXZ magma was about 790℃ and the depth of the magma reservoir around 7 km,the same values as estimated for ME.QXZ had a viscosity of 10^(5.5)-10^(9) Pa s and a velocity of 3-10 km/yr.The emplacement time was 0.5-1.6yr and the flow rate 0.48-1.50 m^(3)/s.These values lie within the range estimated for other rhyolitic flows worldwide.The QXZ lava originated through a mixed explosive-effusive activity with the obsidian resulting from the ascent of undercooling,degassing and the fragmentation of magma along the conduit walls,whereas the aphanitic component testifies to the less undercooled and segregated flow at the center of the conduit.The QXZ lava demonstrates the extensive history of the ME magma chamber.展开更多
With mineral-melt thermobarometers,reconstruction of P-T-depth history of magmas can be established for vol-canic rocks.The pillow lava of Hantangang River Basalt is suitable for the study as it bears narrow compositi...With mineral-melt thermobarometers,reconstruction of P-T-depth history of magmas can be established for vol-canic rocks.The pillow lava of Hantangang River Basalt is suitable for the study as it bears narrow compositional range resulting from little or no fractional crystallization or crustal assimilation and shows evidence of rapid magma ascent.The established thermodynamic model covers the pathway from the magma source depth to the eruption.The model shows that the pillow lava originated at the depths of~85-100 km by fluid ascent from a stagnant slab.This range corresponds to the depth that encompasses the uppermost asthenosphere to the lowermost lithosphere corresponding to the upper garnet to the lower spinel sta-bility fields of the mantle.Subsequently,the melt rose to~66-71 km depth where a primary magma reservoir was generated possibly due to existence of a possible local discontinuity within the upper mantle.The magma uprose rapidly from~61 to~20 km or even to a shallower depth with crystallization of dendritic clinopyroxene and titano-magnetite,due to dehydration of magma.Magma ascent slowed down near the surface possibly due to the volcanic channel split into two or more toward the vents.The model can be applied to other volcanic areas composed of less evolved rocks.展开更多
The study presents the results of over 30,000 numerical analyses on the stability of lava tubes under lunar conditions.The research considered random irregularities in cave geometry and their impact on stability,with ...The study presents the results of over 30,000 numerical analyses on the stability of lava tubes under lunar conditions.The research considered random irregularities in cave geometry and their impact on stability,with a particular focus on the geometric characteristics of identified collapses.We propose a procedure for extracting the collapse areas and integrating it into the stability analysis results.The results were examined to assess the possibility of describing the geometry characteristics of collapses using commonly applied probability density distributions,such as normal or lognormal distribution.Our aim is to facilitate future risk assessment of lunar caves.Such an assessment will be essential prior to robotically exploring caves beneath the lunar surface and can be extended to be used for planetary caves beyond the Moon.Our findings indicate that several collapse characteristics can be represented by unimodal probability density distributions,which could significantly simplify the candidate selection process.Based on our results,we also highlight several key directions for future research and suggested implications related to their future exploration.展开更多
The Moon,as the closest celestial body to the Earth,plays a pivotal role in the progression of deep space exploration,and the establishment of research outposts on its surface represents a crucial step in this mission...The Moon,as the closest celestial body to the Earth,plays a pivotal role in the progression of deep space exploration,and the establishment of research outposts on its surface represents a crucial step in this mission.Lunar lava tubes are special underground caves formed by volcanic eruptions and are considered as ideal natural shelters and scientific laboratories for lunar base construction.This paper begins with an in-depth overview of the geological origins,exploration history,and distribution locations of lunar lava tubes.Subsequently,it delves into the presentation of four distinctive advantages and typical concepts for constructing bases within lava tubes,summarizing the ground-based attempts made thus far in lunar lava tube base construction.Field studies conducted on a lava tube in Hainan revealed rock compositions similar to those found during the Apollo missions and clear lava tube structures,making it a promising analog site.Lastly,the challenges and opportunities encountered in the field of geotechnical engineering regarding the establishment of lunar lava tube bases are discussed,encompassing cave exploration technologies,in-situ testing methods,geomechanical properties under lunar extreme environments,base design and structural stability assessment,excavation and reinforcement techniques,and simulated Earth-based lava tube base.展开更多
目的探讨透视触发3DLAVA技术对肝实质病变及血管的显示情况。方法21例经手术病理或治疗后确诊的肝实质内病变的患者选入本次研究。应用1.5T扫描仪（GE Excite HD Twinspeed1.5T）。动脉期应用透视触发技术,以确保肝脏动脉早期的成功显...目的探讨透视触发3DLAVA技术对肝实质病变及血管的显示情况。方法21例经手术病理或治疗后确诊的肝实质内病变的患者选入本次研究。应用1.5T扫描仪（GE Excite HD Twinspeed1.5T）。动脉期应用透视触发技术,以确保肝脏动脉早期的成功显示。对所有时相的主动脉、门脉、肝实质及病灶绘制信号强度-时间曲线,同时对动脉相及门脉相采用最大密度投影（MIP）,观察肝动脉及门脉的显示情况。结果21例病人均获得高质量6~8个时相的全肝图像。信号强度-时间曲线显示所有病例的门脉及肝实质均在第三个时相达到峰值,而不同病灶的信号强度-时间曲线各有特点,对诊断能够提供更多的帮助。MIP结合原图能清楚显示肝固有动脉的3~4级分支,对门脉系统的显示率达到100%。结论透视触发3DLAVA技术能够清楚显示肝实质病变的动态增强特点,能够清楚显示肝动脉、门脉的分支及其与病灶的关系。展开更多
目的探讨MR 3D LAVA(LAVA)动态强化扫描对于Budd-Chiari综合征的诊断价值。方法 21例Budd-Chiari综合征患者均行MR LAVA动态强化扫描,对各时相扫描分别进行MIP、MPR处理,并对图像质量和血管显示情况进行分析。结果动脉时相的3D MIP对肝...目的探讨MR 3D LAVA(LAVA)动态强化扫描对于Budd-Chiari综合征的诊断价值。方法 21例Budd-Chiari综合征患者均行MR LAVA动态强化扫描,对各时相扫描分别进行MIP、MPR处理,并对图像质量和血管显示情况进行分析。结果动脉时相的3D MIP对肝动脉观察的满意率达90.4﹪,第三时相冠状位MIP与多层面重组结合对门静脉、下腔静脉和肝静脉的显示满意率达100%。结论对于Budd-Chiari综合征,MR 3D LAVA动态强化扫描技术不仅能准确地显示肝动、静脉的解剖形态及病变,同时还能全面地观察肝脏及周围其他脏器的情况。展开更多
基金funded by the National Natural Science Foundation of China(Grant Nos.41972313 and 41790453)the Engineering Research Center of Geothermal Resources Development Technology and Equipment,Ministry of Education,Jilin University。
文摘The 7 ka old Qixiangzhan lava flow(QXZ,Tianchi volcano)represents the last eruptive event before the 946 CE,caldera-forming‘Millennium’eruption(ME).Petrographic,whole rock,mineral composition,Sr-Nd isotopic data on QXZ show that:(a)the lava consists of two components,constituted by comenditic obsidian fragments immersed in a continuous,aphanitic component;(b)both components have the same geochemical and isotopic variations of the ME magma.The QXZ and ME comendites result from fractional crystallization and crustal assimilation processes.The temperature of the QXZ magma was about 790℃ and the depth of the magma reservoir around 7 km,the same values as estimated for ME.QXZ had a viscosity of 10^(5.5)-10^(9) Pa s and a velocity of 3-10 km/yr.The emplacement time was 0.5-1.6yr and the flow rate 0.48-1.50 m^(3)/s.These values lie within the range estimated for other rhyolitic flows worldwide.The QXZ lava originated through a mixed explosive-effusive activity with the obsidian resulting from the ascent of undercooling,degassing and the fragmentation of magma along the conduit walls,whereas the aphanitic component testifies to the less undercooled and segregated flow at the center of the conduit.The QXZ lava demonstrates the extensive history of the ME magma chamber.
基金supported by the 2021 Research Project for UNESCO Hantangang River Global Geopark supported by Gyeonggi Provincial Office(Grant No.20210606641-00)Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.2019R1A6A1A03033167).
文摘With mineral-melt thermobarometers,reconstruction of P-T-depth history of magmas can be established for vol-canic rocks.The pillow lava of Hantangang River Basalt is suitable for the study as it bears narrow compositional range resulting from little or no fractional crystallization or crustal assimilation and shows evidence of rapid magma ascent.The established thermodynamic model covers the pathway from the magma source depth to the eruption.The model shows that the pillow lava originated at the depths of~85-100 km by fluid ascent from a stagnant slab.This range corresponds to the depth that encompasses the uppermost asthenosphere to the lowermost lithosphere corresponding to the upper garnet to the lower spinel sta-bility fields of the mantle.Subsequently,the melt rose to~66-71 km depth where a primary magma reservoir was generated possibly due to existence of a possible local discontinuity within the upper mantle.The magma uprose rapidly from~61 to~20 km or even to a shallower depth with crystallization of dendritic clinopyroxene and titano-magnetite,due to dehydration of magma.Magma ascent slowed down near the surface possibly due to the volcanic channel split into two or more toward the vents.The model can be applied to other volcanic areas composed of less evolved rocks.
基金The work was performed based on the research project no.2023/51/D/ST10/01956,financed by the National Science Center,Poland.
文摘The study presents the results of over 30,000 numerical analyses on the stability of lava tubes under lunar conditions.The research considered random irregularities in cave geometry and their impact on stability,with a particular focus on the geometric characteristics of identified collapses.We propose a procedure for extracting the collapse areas and integrating it into the stability analysis results.The results were examined to assess the possibility of describing the geometry characteristics of collapses using commonly applied probability density distributions,such as normal or lognormal distribution.Our aim is to facilitate future risk assessment of lunar caves.Such an assessment will be essential prior to robotically exploring caves beneath the lunar surface and can be extended to be used for planetary caves beyond the Moon.Our findings indicate that several collapse characteristics can be represented by unimodal probability density distributions,which could significantly simplify the candidate selection process.Based on our results,we also highlight several key directions for future research and suggested implications related to their future exploration.
基金supported by the National Natural Science Foundation of China(Nos.52125903 and 52339001).
文摘The Moon,as the closest celestial body to the Earth,plays a pivotal role in the progression of deep space exploration,and the establishment of research outposts on its surface represents a crucial step in this mission.Lunar lava tubes are special underground caves formed by volcanic eruptions and are considered as ideal natural shelters and scientific laboratories for lunar base construction.This paper begins with an in-depth overview of the geological origins,exploration history,and distribution locations of lunar lava tubes.Subsequently,it delves into the presentation of four distinctive advantages and typical concepts for constructing bases within lava tubes,summarizing the ground-based attempts made thus far in lunar lava tube base construction.Field studies conducted on a lava tube in Hainan revealed rock compositions similar to those found during the Apollo missions and clear lava tube structures,making it a promising analog site.Lastly,the challenges and opportunities encountered in the field of geotechnical engineering regarding the establishment of lunar lava tube bases are discussed,encompassing cave exploration technologies,in-situ testing methods,geomechanical properties under lunar extreme environments,base design and structural stability assessment,excavation and reinforcement techniques,and simulated Earth-based lava tube base.
文摘目的探讨透视触发3DLAVA技术对肝实质病变及血管的显示情况。方法21例经手术病理或治疗后确诊的肝实质内病变的患者选入本次研究。应用1.5T扫描仪（GE Excite HD Twinspeed1.5T）。动脉期应用透视触发技术,以确保肝脏动脉早期的成功显示。对所有时相的主动脉、门脉、肝实质及病灶绘制信号强度-时间曲线,同时对动脉相及门脉相采用最大密度投影（MIP）,观察肝动脉及门脉的显示情况。结果21例病人均获得高质量6~8个时相的全肝图像。信号强度-时间曲线显示所有病例的门脉及肝实质均在第三个时相达到峰值,而不同病灶的信号强度-时间曲线各有特点,对诊断能够提供更多的帮助。MIP结合原图能清楚显示肝固有动脉的3~4级分支,对门脉系统的显示率达到100%。结论透视触发3DLAVA技术能够清楚显示肝实质病变的动态增强特点,能够清楚显示肝动脉、门脉的分支及其与病灶的关系。
文摘目的探讨MR 3D LAVA(LAVA)动态强化扫描对于Budd-Chiari综合征的诊断价值。方法 21例Budd-Chiari综合征患者均行MR LAVA动态强化扫描,对各时相扫描分别进行MIP、MPR处理,并对图像质量和血管显示情况进行分析。结果动脉时相的3D MIP对肝动脉观察的满意率达90.4﹪,第三时相冠状位MIP与多层面重组结合对门静脉、下腔静脉和肝静脉的显示满意率达100%。结论对于Budd-Chiari综合征,MR 3D LAVA动态强化扫描技术不仅能准确地显示肝动、静脉的解剖形态及病变,同时还能全面地观察肝脏及周围其他脏器的情况。
