Crust and Upper Mantle Electrical Resistivity Structure in the Panxi Region of the Eastern Tibetan Plateau and Its Significance

The Panxi region is located in the frontal zone of positive squeezing subduction and side squeezing shearing between the Indian plate and the Eurasian plate. The long-period magnetotelluric （LMT） and broadband magnetotelluric （MT） techniques are both used to study the deep electrical conductivity structure in this region; magnetic and gravity surveys are also performed along the profile. According to the 2-D resistivity model along the Yanyuan-Yongshan profile, a high- conductivity layer （HCL） exists widely in the crust, and a high-resistivity block （HRB） exists widely in the upper mantle in general, as seen by the fact that a large HCL exists from the western Jinpingshan tectonic zone to the eastern Mabian tectonic zone in the crust, while the HRB found in the Panxi tectonic zone is of abnormally high resistivity in that background compared to both sides of Panxi tectonic zone. In addition, the gravity and magnetic field anomalies are of high value. Combined with geological data, the results indicate that there probably exists basic or ultrabasic rock with a large thickness in the lithosphere in the Panxi axial region, which indicates that fracture activity once occurred in the lithosphere. As a result, we can infer that the high-resistivity zone in the Panxi lithosphere is the eruption channel for Permian Emeishan basalt and the accumulation channel for basic and ultrabasic rock. The seismic sources along the profile are counted according to seismic record data. The results indicate that the most violent earthquake sources are located at the binding site of the HRB and the HCL, where the tectonic activity zone is generally acknowledged to be; however, the earthquakes occurring in the HCL are not so violent, which reflects the fact that the HCL is a plastic layer, and the fracture threshold of a plastic layer is low generally, making high stress difficult to accumulate but easy to release in the layer. As a result, a higher number of smaller earthquakes occurred in the HCL at Daliangshan tectonic zone, and violent earthquakes occurred at the binding site of high- and low-resistivity blocks at the Panxi tectonic zone.

Assessment and Risk Zonation of Landslides in Panxi Area Based on 3S Technology

Based on field survey located by GPS, it is obtained landslides＇ location and distribution information by the method of remote sensing in this paper. The vector data of environmental factors that breed and induce landslides such as the elevation, the slope, the vegetation cover, the lithology, the rainfall and so on are gained using GIS（geographical information system） techniques of spatial analysis. All the data obtained are managed through building landslide management system. At the same time, the system is made the platform to appraise the relationship between the distribution of landslides and the environmental factors. The results indicate： landslides take place relatively easily in the slope range between 10° and 25°; most landslides are in the mixed area of bush and grass with a coverage degree of from 20° to 65°; the distribution of landslides has a positive relationship with the distribution of annual rainfall. The risk degree of Panxi Area is zoned and mapped by the model of liner stack using GIS technique, and the result indicates： the place of high risk degree is the belt of Panzhihua-Miyi-Dechang-Mugu and southeast of Huili county and Huidong county,and area is about 512 707 hm^2.

Geochemistry of the Limahe Intrusion in the Panxi District, SW China:Discussion on the Relationship to the Emeishan Basalts

The Limahe intrusion is a typical rock hosting Cu-Ni sulfide deposit in the Panxi district. The major element, trace element and Sr-Nd isotopic geochemical data are reported in this study both firstly and systemically. Age-corrected （87Sr/86Sr） and εNd（t） isotope values, ranging from 0.687062 to 0.709298, from -0.6 to -4.13 respectively, are partly overlap the field of the Emeishan basalt and OIB, and they lie between upper crust and OIB generally. The similar patterns between the Limahe intrusion and the picrites of the Emeishan large igneous province imply the genetic relationship to the Emeishan basalts. Their lower Nb/U （〈30）, higher （La/Nb）pM and （Th/Ta）pM ratio values （〉1） indicate contamination of the upper crust material. The correlation between MgO and major oxides reflects the fractional crystallization of olivine, clinopyroxene and minor plagioclase in the deep-seated chamber. Therefore increased SiO2 and lowered FeO by the upper crustal contamination may trigger immiscible sulfide melt, which then flowed along the structural fracture and intruded into gabbrodiorite, resulting in the formation of Cu-Ni sulfide orebody.

Toxic Plant Resources in Panxi Area

Panxi Area is abundant in plant resources, among which toxic plants are of great value in terms of exploitation. This paper is an initiative study （via field as well as literature investigation） of the categories, distributions, and reserves of toxic plant resources in Panxi Area. The study reveals that there are 51 families （210 species） of toxic plants evenly distributed in Panxi Area, of which more than 40 species grow in all counties in the area, and more than 14 species total a reserve more than 1.0×10^5 kg. These toxic plants are of great applications to medicine, gardening, biopesticide industry, environmental engineering, and oil manufacturing. Rhododendron molle, Anisodus acutangulus, Arisaema erubesocens, Stellera chamaejasme, Rhytolacca acinosa, Rheum officinale, and Azadiralta indica etc are the typical toxic plants with great value of exploitation in Panxi Area.

The Results and Comparison of "Logical-Tree" Seismic Zoning in the Panxi Area

On the basis of the technological route of seismic hazard analysis,the methods for determining seismicity parameters,such as b value,annual occurrence rate,and the seismic spatial distribution function,are discussed.Then,the seismic intensity zoning in Panxi area in Southwest China is carried out by applying the "logical-tree,"which is made up of multi-parameter schemes.It is clearly shown from the results that seismic intensity zoning is influenced by many uncertain factors and it is necessary to seek a certain balance between seismic safety and investment interest and a good way,with the present limited knowledge level,to obtain seismic intensity zoning is through the "logical-tree" method.

Study of seismic tomography in Panxi paleorift area of southwestern China——Structural features of crust and mantle and their evolution

Structural features of the typical continental paleorift in Panxiarea are revealed by seismic tomography. (1) In the profile along the minor axis of Panxi paleorift, we found alternating high and low-velocity strips existing at different depths in the crust, presenting itself as a "sandwich" structure. The existence of these high and low-velocity anomaly strips is related to the basal lithology in the rift area. (2) An addition layer with velocity values of 7.1-7.5 km/s and 7.8 km/s exists from the base of lower crust to uppermost mantle and its thickness is about 20 km. Some study results indicate that the addition layer results from the invasion of mantle material. (3) A lens-shaped high-velocity body surrounded by relatively low-velocity material is observed at depths of 110-160 km between Huaping and Huidong in the axis of the paleorift. This is the first time to discover it in the upper mantle of the paleorift. Based on the results of geology, petrology and geochemistry, we infer that the formation of the addition layer and the lens-shaped high-velocity body in the upper mantle are related to the deep geodynamic process of generation, development and termination of the rift. On the one hand, the upwelling of asthenosphere mantle caused partial melting, and then the basaltic magma from the partial melted material further resulted in underplating and formed the crustal addition layer. On the other hand, the high-density content of mineral facies was increased in the residual melted mass of intensely depleted upper mantle, formed by basalt withdrawing. The solid-melt medium in the depleted upper mantle was mainly an accumulation of garnet and peridotite because the heating effect of lithosphere was relatively weakened in the later riftogenesis, so that a lens-shaped high-density and high-velocity zone was produced in the upper mantle. The results indicate that the energy and material exchange between asthenosphere and lithosphere and remarkable underplating would have an important effect on the material state and propagation of seismic wave in the lower crust, crust-mantle interface, asthenosphere and lithosphere. This process possibly is an important mechanism on the growth of continental crust and the evolution of deep mantle.

Volatile and C-H-O isotopic compositions of giant Fe-Ti-V oxide deposits in the Panxi region and their implications for the sources of volatiles and the origin of Fe-Ti oxide ores

The Panzhihua,Hongge,and Baima Fe-Ti-V oxide deposits in the Panzhihua-Xichang(Panxi) region are hosted in large layered mafic-ultramafic intrusions.The layered intrusions intrude either the Neoproterozoic Dengying Formation,composed mainly of limestone,or the Paleoproterozoic Hekou Formation,composed of meta-sedimentary-volcanic rocks.It remains unclear if the wall rocks have been involved during the fractionation of magmas and have affected the sequence of crystallization of Fe-Ti oxide.Volatiles and their C-H-O isotopic compositions of magnetite,apatite,clinopyroxene,and plagioclase of different types of ores from the three intrusions are analyzed using a technique of stepwise heating mass spectrometer to evaluate the role of wall rocks in the formation of Fe-Ti oxide ores.Volatiles released from magnetite are composed mainly of H 2 O and CO 2,whereas the other minerals are composed mainly of H 2 O,CO 2 and H 2.At 800-1200°C temperature interval,the average 13 C values of CO 2 of all the minerals from the three intrusions range from 7.7‰ to 13.5‰ and the average 18 O CO 2 values from 19.1‰ to 19.5‰,which are scattered in a mixed field with basalt and the two types of wall rocks as end-members,indicating that CO 2 from the wall rocks may have been involved in the magmas from which the three intrusions formed.At 400-800 C temperature interval,both 13 C values(13.7‰ to 17.9‰ on the average) and 18 O values(16.2‰ to 19.2‰ on the average) of CO 2 of all the minerals are lower than those for 800-1200 C temperature interval,and much closer to the values of the wall rocks.Abundant H 2 O released at the 400-800 C temperature interval has relatively low D values ranging from 90‰ to 115‰,also indicating the involvement of fluids from the wall rocks.The average bulk contents of volatiles released from magnetite of the Hongge,Baima,and Panzhihua intrusions are 4891,2996,and 1568 mm 3 STP/g,respectively,much higher than those released from other minerals in total,which are 382,600,and 379 mm 3 STP/g,respectively,indicating that magnetite crystallized from magmas with much more volatiles than other minerals.This can be interpreted as that crystallization of clinopyroxene and plagioclase in the early fractionation of magmas resulted in volatiles such as H 2 O that were eventually enriched in the residual magmas and,at the same time,fluids from the wall rocks may have been involved in the magmas and were trapped in magnetite,which crystallized later than clinopyroxene and plagioclase.

DETERMINATION OF THE THICKNESS OF LITHOSPHERE BY GEOTHERMAL DATA——CASE STUDIES IN PANXI REGION

Ⅰ. DATA1. Terrestrial Heat FlowTo date, 13 reliable heat flow values have been obtained in the Panxi region and were published in Refs. [1, 2]. For use, these data were cited and synthesized in Table 1.

Hydrothermal sedimentation and lead-zinc deposit in Dengying formation of the Sinian system in Panxi region

IN addition to vanadium titano-magnetite, lead-zinc ore is also one of the mineral resources with great exploring potentiality in the Panxi region of Sichuan Province, China. In the carbonate rock strata of theSinian Dengying Formation which account for about 3.5%-11.4% of the total thickness of the strataexposed in the Panxi region there are quite a number of the Pb-Zn deposits that account for 53.4% of thetotal Pb-Zn ore reserve in the whole region. Furthermore, some large Pb-Zn deposits such as the Tianbaoshan Pb-Zn deposit in Huili, the Daliangzi Pb-Zn deposit in Huidong and the Yinchanggou Pb-Zn deposit in Ningnan are also hosted in the Sinian Dengying Formation. Why? Previous studies indicated that the high background values of Pb and Zn, favorable lithofacies andpaleogeographic conditions and good ore-hosting structures made the Sinian Dengying Formation a pre-

HEAT FLOW MEASUREMENTS IN PANZHIHUA-XICHANG(PANXI) PALEORIFT ZONE, SW CHINA

Heat flow measurements are of great significance in rift studies. The Panxi area has. been considered to be a paleorift zone of the Hercynian-Indosinian period. For a long time, the geological and geophysical community are greatly concerned about the thermal state and the possibility of the existence of high heat flow in this region. And great efforts and research work have been made by joint geothermal study program of

GEOCHEMISTRY OF IGNEOUS ROCK IN PANXI RIFT

In this paper the petrogenesis and magmatism of igneous rocks in the Panxi Rift are discussed based on the major element, transition metallic element, REE and other trace element analysis data of more than 40 samples.According to major element data, a feature of bimodal distribution is displayed. The transition metal patterns show that Cr and Ni are highly depleted and Ti is highly concentrated, reflecting a rather complex history of crystallization differentiation.The distribution patterns of hygromagmatophile element abundance of basalts normalized with primary mantle values are shown to be intermediate between those of alkali basalts and continental tholeiites. This provides evidence suggesting that the basalts were generated in a rift tectonic environment, and that the primary magma came deeply from the primary mantle as a result of partial melting of garnet lherzolite.

景观人类学视角下的泮溪酒家保护更新研究

基于景观人类学的理念和方法指导泮溪酒家历史环境的保护更新,以空间生产和场所构建的理论结合人类学田野调查、结构化访谈及大数据分析等方法研究泮溪酒家及所处西关历史环境的“空间”“场所”景观及二者“多相”共生的情况。在此基础上结合泮溪酒家保护更新的实践,以“空间”和“场所”视角扩大研究范围,串联象征符号,挖掘当地居民日常生活实践与社会关系,生产与构建出具有地方特色且符合当地居民情感记忆的景观。最后以“多相律”理论探求内外景观的统一与融合共生,为中国城乡建设中的历史环境保护更新提供新视角与方法论参考。

攀西某钒钛磁铁矿中钛的赋存状态研究

对攀西某钒钛磁铁矿化学组成、矿物种类及含量、含钛矿物能谱微区成分、矿石中TiO_(2)的平衡概算、含钛矿物产出形式、钛铁矿粒度及解离度等进行详细研究,查清了矿石难选的原因,综合分析了钛精矿的技术指标以及影响选钛效果的主要矿物学因素,可为开发利用攀西某矿产资源提供详细的科学依据。

川西高原和攀西地区不同级别短时强降水环境参量特征对比分析

利用2010—2021年5—9月川西高原和攀西地区62个国家级自动站逐小时观测资料及时间分辨率为1 h的ERA5再分析资料,对比分析了两区域不同级别短时强降水发生发展过程中水汽、热力和垂直风切变等环境参量特征。结果表明:川西高原和攀西地区短时强降水主要集中在6—8月,午后至前半夜是川西高原短时强降水的高发时段,攀西地区则表现出明显的夜雨特征。就川西高原而言,较好的水汽、热力条件和较强的垂直风切变、上升运动均有利于高级别短时强降水的产生;不同级别短时强降水的CAPE值差异显著,1100 J·kg^(−1)可作为判断是否出现20 mm·h^(−1)以上短时强降水的参考阈值。就攀西地区而言,不同级别短时强降水在暖云层厚度、700 hPa比湿、700 hPa假相当位温、CAPE、0~3 km垂直风切变等环境参量的值域分布上均存在明显差异;当700 hPa比湿大于13 g·kg^(−1)、CPAE值超过1100 J·kg^(−1)、0~3 km垂直风切变达到10 m·s^(−1)时,极易出现50 mm·h^(−1)以上的短时强降水。

潘谢矿区13-1煤层煤层气地质特征及顶板分段压裂水平井抽采效果探讨

淮南煤田为高瓦斯煤田,煤层碎软低渗,瓦斯抽采难度大。在分析淮南潘谢矿区13-1煤层储层特征的基础上,基于顶板岩石脆性指数和煤层三向地应力探讨煤层顶板分段压裂水平井技术地质条件的可行性,并施工PYD-01顶板分段压裂水平井开展抽采工程试验。结果表明:潘谢矿区13-1煤层为全区稳定可采煤层,厚度大,埋藏深度适中,含气量较高,煤层气成藏条件较好。砂质泥岩脆性指数大于泥岩,三向应力场类型主要为σh,max>σv>σh,min,具备实施顶板分段压裂水平井技术地质条件。PYD-01井抽采第350 d时通过井下定向长钻孔密闭取心测试发现在距水平段79m处瓦斯含量由11.85m3/t降低7.94m3/t;在水平段50m处瓦斯压力由6.8MPa降至2.4MPa且在孔内发现压裂砂,验证了顶板分段压裂水平井技术的可行性。

攀西太和钒钛磁铁矿中钴的分布规律及赋存状态

这是一篇工艺矿物学领域的论文。钴是重要的战略金属,主要以共-伴生元素的形式分布于金属矿床中。攀西地区的钒钛磁铁矿矿床是我国最大的钒钛铁资源基地,其矿床中伴生了大量的钴资源,但富钴矿石中钴在矿物相之间的分布规律及微观的赋存状态还未被查明。本文选择攀西地区太和钒钛磁铁矿矿床作为研究对象,利用化学分析、光学显微镜、扫描电镜(SEM-BSE)、X射线衍射分析(XRD)、高级矿物鉴定和表征系统(AMICS)、电子探针(EPMA)等分析技术对矿床中典型的富钴矿石进行了化学成分、矿物组成以及Co元素在不同矿物间分布规律及赋存状态进行了研究,研究结果表明富钴样品矿物中硫化物具有较高的钴含量,而铁钛氧化物中钴含量较低,其他矿物中几乎不含有钴,钴的分布规律表明其主要分布于硫化物中,少量分布于铁钛氧化物以及脉石矿物中。样品中钴元素具有独立矿物-硫钴镍矿和类质同象两种赋存状态。研究结果为该地区钴资源的综合利用提供矿物学依据。

攀西地区二叠纪碱性岩成因及其铌钽成矿作用研究进展

铌(Nb)、钽(Ta)元素是重要的战略性关键金属资源,碱性岩因富集铌钽等稀有、稀土元素而备受学者们关注。近年来,峨眉山大火成岩省内部带攀西地区发育的一系列二叠纪过碱性-准铝质-过铝质正长岩和花岗岩及其相关铌钽矿床在成岩成矿时代、地球化学特征、岩石成因及铌钽富集机制等方面取得了一些重要研究进展。主要认识有:在地幔柱轴部,地幔苦橄岩部分熔融形成峨眉山高钛玄武质岩浆,其在岩浆房中发生分离结晶和液态不混溶作用,形成小规模的A型花岗岩和碱性-准铝质正长岩。底侵的幔源岩浆对流为基性辉长岩部分熔融提供大量的热能,形成广泛分布的过碱性-准铝质正长岩和花岗岩。与此同时,少量新生地壳或扬子板块基底参与部分熔融过程则会形成过铝质花岗岩。研究表明,铌钽元素富集过程受岩浆结晶分异和热液交代两个演化阶段共同控制。源自地幔的碱性岩浆通过结晶分异作用优先结晶出斜长石、角闪石、磷灰石等矿物,导致Nb、Ta元素在正长岩体中得到初步富集。从岩体中出溶的富F-Na热液交代原岩,并发生钠长石化、霓石化、萤石化等蚀变作用。早期岩浆成因的铌钽矿物因交代而裂解,使Nb、Ta元素被重新活化、迁移、沉淀形成热液烧绿石和榍石。

基于多元要素协同的乡村精明收缩路径研究

精明收缩是人、地、资源的优化配置,是乡村高质量发展的有效途径。文章以精明收缩理论为指导,以福建省福鼎市溪镇18个行政村(223个自然村)为例,分析城镇化背景下乡村人口、产业、职能、空间收缩的基本表征,探讨乡村收缩的机制,认为“人口外流—产业收缩”和“人口外流—服务设施不足”两个恶性循环,是加速乡村收缩的动因,二者分别映射于村庄空间,引发农村人、地、资源关系失调。由此提出人口、产业、空间、职能协同发展的乡村精明收缩路径:人口—产业协同,产业转型升级是先导,推动人口结构的重塑;人口—空间协同,从聚集核、空间模式、空间综合整治方面提出精明收缩路径;人口—职能协同,探讨服务职能的分化、上移及生活圈的建构。

攀西地区5个油橄榄品种细根形态特征及碳氮磷化学计量特征研究

探究油橄榄(Olea europaea)细根形态特征和养分分配格局对油橄榄引种栽培生产具有重要意义。通过对攀西地区5个油橄榄品种的细根直径、比表面积、比根长、组织密度等形态参数和碳(C)、氮(N)、磷(P)化学计量特征研究,探讨细根形态和养分含量在不同油橄榄品种细根根序等级间的差异和与土壤理化性质间的关联。研究结果表明:(1)随着根序等级的增加,细根直径、组织密度呈明显的递增趋势,比表面积、比根长则呈现出明显递减趋势;(2)细根C含量、C:N、C:P随根序的增加而逐渐增大,细根N、P含量基本呈现随着根序的增加而降低,除白橄榄外,细根N:P总体呈现随着根序序级增加而增加的趋势;(3)细根C含量与土壤理化特征指标间均无显著相关性;细根N含量与土壤C、P含量间存在显著正相关(p<0.05),与土壤C:N间存在着极显著的正相关(p<0.01);细根P含量与土壤C、P含量及C:N间存在极显著正相关(p<0.01),与土壤N:P间存在显著负相关(p<0.05);细根C:N与土壤C:N呈显著负相关(p<0.05),细根N:P、C:P与土壤理化特征指标间无显著的相关性。

基于TVDI的攀西地区干旱时空变化特征研究

利用MODIS地表温度数据(LST)和归一化植被指数(NDVI)构建Ts-NDVI特征空间,通过计算温度植被干旱指数(TVDI)详细分析了攀西地区2001—2020年干旱时空变化规律。结果表明:(1)从时间角度来看,20年间攀西地区TVDI年均值介于0.5481~0.5820,以-0.0001·a^(-1)速率缓慢减小,且在2001年和2009年出现大范围中旱。季节性干旱特点表现为冬干春旱,各季TVDI均值分别为冬季0.5618、春季0.6058、夏季0.5590、秋季0.5365,表明冬、春两季较夏、秋两季更容易形成干旱。TVDI月均最大值出现在5月份,为0.6089;最小值出现在9月份,为0.5204;每年2—6月以中旱为主;7月起旱情减轻,转为轻旱;10月起旱情逐渐加重。(2)从空间角度来看,攀西地区旱情变化趋势南北差异明显,南部干旱发生的频率和范围大于北部地区,呈现出中部、南部及西南部高,北部、西北部及东北部低的空间分布特征。(3)从典型干旱年份来看,攀西地区2001年、2006年和2011年春旱耕地在空间分布上具有一定的相似性。其中,受中旱的耕地主要分布在攀西北部和中部;而受重旱的耕地主要集中分布在攀西西南部。研究结果表明,2001—2020年攀西地区旱情稍有缓解,不同季节间干旱差异性较大,干旱范围以攀西中部和南部为主。