GEOCHEMICAL CHARACTERISTICS OF GRANITES AND ITS STRUCTURAL GENETIC ENVIRONMENT IN THE NANDAN-HECHI METALLOGENETIC BELT, NORTHWEST GUANGXI

The Nandan-Hechi metallogenetic belt is the most important tin-polymetallic producing district in China, and is the location of the Dachang super-large tin deposit. Based on the detailed field investigation and isotopic data, the stages of magmatic activity in the Nandan-Hechi metallogenetic belt have been lined out in this paper. Through the study about the geochemical characteristics of different granites, and by using ω(Al2O3)-ω(SiO2), ω(TFeO)/[ω(TFeO)+ω(MgO)]-ω(SiO2), AFM, ACF and Rb-Yb+Ta, Rb-Y+Nb, Ta-Yb, Nb-Y discrimination diagrams in combination with regional geological setting analysis, the authors carried out analyses about the structural environment for the formation of the granites, and discussed the structural environment and dynamic setting for the large scale mineralization in this area. Our study indicates that the majority of the granites in Nandan-Hechi metallogenetic belt belong to the POG type, while the later stage alaskite belongs to the RRG+CEUG type. The granites were formed at the stage of structural transformation from postorogenic phase to intraplate setting. But the major structural environment is characterized by steady regional extension. The formation age for the granites coincides with the time for this transformation, and this translation environment is favored for large-scale metallogenesis.

Geochronological Constraints on the Haftcheshmeh Porphyry Cu-Mo-Au Ore Deposit, Central Qaradagh Batholith, Arasbaran Metallogenic Belt, Northwest Iran

The Haftcheshmeh porphyry Cu-Mo-Au deposit in the Arasbaran metallogenic belt （AMB） of NW Iran contains more than 185 Mt of ore, with a grade ranging from 0.3% to 0.4%. It is hosted within a porphyritic diorite to granodiorite intruded into an older gabbro - diorite intrusion. 40Ar/39Ar analyses of primary magmatic hornblende from the granodiorite porphyry and gabbro - diorite show plateau ages of 26.41 ± 0.59 Ma, with an inverse isochron age of 25.9 ± 1.0 Ma and a plateau age of 27.47 ± 0.17 Ma, with an inverse isochron age of 27.48 ± 0.35 Ma for these two rock types, respectively. Comparing these new age data with those from the nearby Sungun （20.69 ± 0.35 Ma） and Kighal porphyry deposits defines a northwest-southeast Cu-Mo-Au mineralization zone extending for 20 km over the time span of-27 to 20 Ma. Geochemically, Haftcheshmeh rocks are calc-alkaline with high potassium affinities with tectonic setting in relation to volcanic arc setting. Large ion lithophile elements （LILE） such as Th, U and K show enrichment on a primitive mantle normalized diagram （specially Pb）, and are depleted in high field strength elements （HFSE） such as Ti and Nb, pointing to a mantle magma source contamination with crustal materials by subducted oceanic crust.

Construction of Silk Road Economic Belt and Industrial Selection of Minority Areas in Northwest China

Construction of Silk Road Economic Belt is a giant engine for the economic upgrading of China.Minority areas in Northwest China since then has become a forward position for the opening to the west,which is extremely significant for expanding the hinterland of Chinese economic development,activating economic development in inland and border areas,promoting the open economic development in central and west China,and also forming a new growth pole of Chinese economy.Optimization of industrial selection can promote economic development,constant economic growth of the northwest minority areas and the construction of Silk Road Economic Belt requires the optimization and adjustment of industrial selection,cultivation of competitive industries with market prospects,and formation of new economic growth points.Minority areas in northwest China have a vast territory and abundant resources that are all powerful support for the development of local competitive industries.

塔里木盆地西北缘乌什西次凹的地层系统和构造特征

乌什西次凹位于塔里木盆地西北缘,隶属于库车坳陷的乌什凹陷。它位于南天山主山脉(哈尔克山)和塔里木盆地柯坪—温宿凸起之间。区域构造格局上,这里是塔里木克拉通向西北自然延伸的部分。次凹北缘的阿合奇断裂是南天山造山带和塔里木克拉通的分界。乌什西次凹内发育与柯坪—温宿凸起相似的晚前寒武纪—古生代地层系统,包括寒武系、奥陶系和石炭系的烃源岩。新近系—第四系碎屑岩建造直接不整合于变形的古生代被动大陆边缘碎屑岩—碳酸盐岩沉积建造之上;剖面上,向南天山方向加厚,向塔里木克拉通方向减薄,呈现典型的前陆盆地剖面结构特征。这是一个晚新生代陆内前陆盆地,叠加在晚海西期—燕山期古隆起之上。这里的构造变形主要有3期,分别是中海西期、晚海西期—印支期和晚喜山期。变形以厚皮冲断构造及其相关褶皱为主,薄皮构造不发育。平面上,主构造线走向NE-SW。剖面上,以南天山向塔里木冲断为主。

西北农牧交错带土地利用变化及其生态环境效应研究——以甘肃环县为例

以西北农牧交错带典型区域甘肃环县为研究对象,基于2007、2012、2017年和2022年4期土地利用现状数据,在分析土地利用时空变化的基础上,进一步探究区域生态环境质量指数及生态贡献率变化情况,阐明土地利用变化与生态环境质量之间的相关性。结果表明,环县土地利用面积变化表现为“一减五增”的趋势,仅草地面积减少,其余地类面积均呈增长态势,其中林地面积增幅最大;土地利用变化类型为草地、林地、耕地和建设用地四大地类之间的相互转化,草地转化为耕地对该区域生态恶化的效应最大,草地转化为林地对生态改善的贡献最大,因此,应科学合理规划确定土地利用用途,在保护耕地的基础上,充分发挥草地和林地的正面生态环境效应。

“一带一路”背景下西北五省区域旅游合作发展研究综述

2013年习近平总书记明确提出共建“丝绸之路经济带”和“21世纪海上丝绸之路”的重大倡议,并作为国家中长期发展的重大战略。随着倡议的深入推进,丝绸之路经济带建设工程为中国西北五省区开放发展、协作共赢,创造得天独厚的便利条件。充分发挥“丝绸之路”重要组成部分的带动作用,促进“一带一路”背景下西北地区旅游业发展,对近年来中国知网数据库中的相关文献进行梳理与分析,从研究数量、研究热点与研究内容等方面加以评述,指出今后的研究重点和趋势。通过理论与实践相结合的方式探索在“一带一路”背景下西北五省旅游合作的创新发展。

Geochemistry of Permian Mafic Igneous Rocks from the Napo-Qinzhou Tectonic Belt in Southwest Guangxi, Southwest China: Implications for Arc-Back Arc Basin Magmatic Evolution

The Napo-Qinzhou Tectonic Belt （NQTB） lies at the junction of the Yangtze, Cathaysia and Indochina （North Vietnam） Blocks, which is composed of five major lithotectonic subunits： the Qinzhou-Fangcheng Suture Zone （QFSZ）, the Shiwandashan Basin （SB）, the Pingxiang-Nanning Suture Zone （PNSZ）, the Damingshan Block （DB） and the Babu-Lingma Suture Zone （BLSZ）. On the basis of geochemical compositions, the Permian mafic igneous rocks can be divided into three distinct groups： （1） mafic igneous rocks （Group 1） from the Longjing region in the PNSZ and Hurun region in the BLSZ, which are characterized by intermediate Ti, P and Zr with low Ni and Cr contents; （2） mafic igneous rocks （Group 2） from the Naxiao and Chongzuo region in the DB, characterized by low-intermediate Ti, P and Zr with high Ni and Cr concentrations; and （3） mafic igneous rocks （Group 3） from the Siming region in the Jingxi carbonate platform of the northwestern margin of the NQTB, with intermediate-high Ti, P and Zr and low Ni and Cr contents. The Group 1 rocks yield a weighted mean 206 Pb/ 238 U age of 250.5±2.8 Ma and are geochemically similar to basalts occurring in back-arc basin settings. The Group 2 rocks exhibit geochemical features to those basalts in island arcs, whereas the Group 3 rocks show geochemical similarity to that of ocean island basalts. All three groups are characterized by relatively low ε Nd （t） values （-2.61 to ＋1.10） and high initial 87 Sr/ 86 Sr isotopic ratios （0.705309-0.707434）, indicating that they were derived from a subduction-modified lithospheric mantle and experienced assimilation, fractional crystallization, and crustal contamination or mixing during magmatic evolution. Accordingly, we propose the existence of an arc-back arc basin system that developed along the NQTB at the border of SW Guangxi Province （SW China） and northern Vietnam, and it was formed by continued northwestward subduction of the Cathaysian （or Yunkai） Block under the Yangtze Block, and northeastward subduction of the Indochina Block beneath the Yangtze Block during Permian time.

Discovery and Genetic Mechanism of Basic Granulite in the Altay Orogenic Belt, Xinjiang, NW China

Altay granulite (AG), which represents the product of high-grade metamorphism in the lower crust, was newly found in the Wuqiagou area, Fuyun County in the Altay orogenic belt, Northwest China. It is composed mainly of hypersthene, augite, basic plagioclase, amphibole and brown biotite. Its mineral compositions of amphibole and biotite are rich in Mg/(Mg+Fe2+) and Ti. Geochemically, the AG is enriched in Mg/(Mg+Fe2+) and A12O3, and poor in CaO, with depletion of U, Th, K and Rb contents. Furthermore, geochemical data reflect that the protolith of the AG is igneous-genetic calc-alkaline basalt formed under an island arc environment. The AG has ZREE of 92.38-96.58 ppm and enriched LREE model with weak positive Eu anomaly of 1.09-1.15. In the MORB normalized spider diagram, the AG shows tri-doming pattern with a strong negative Nb anomaly and medium negative P and Ti anomalies, reflecting that the AG has tectonic relation with subduction or subduction-related materials. The P-T conditions of peak metamorphism of the AG are 750-780℃ and >0.6-0.7 GPa. Retrograde metamorphism implies that the protolith of the Altay granulite might undergo a metamorphic process along a clockwise P-T trajectory. Therefore, the formation and evolution of the AG may have a genetic association with continental collision/orogeny and the AG was taken into the Late Paleozoic meta-strata by way of tectonic emplacement.

Sinian hydrocarbon accumulation conditions and exploration potential at the northwest margin of the Yangtze region, China

Based on outcrop, drilling, logging and seismic data, the reservoir forming conditions, reservoir forming model and exploration potential of the ultra-deep Sinian Dengying Formation at the northwest margin of Yangtze craton region were examined.(1) This area is in craton rifting stage from Sinian to Early Cambrian, characterized by syn-sedimentary faults and rapid subsidence, significant sedimentary differences, and development of Dengying Formation platform margins on both sides of the rift.(2) The Sinian–Cambrian in this area has two sets of high-quality source rocks, Doushantuo Formation and Maidiping-Qiongzhusi Formation;of which, the latter has a thickness of 150–600 m and hydrocarbon generation intensity of(100-200)×10;m;/km;.(3) The mounds and shoals in the platform margin of Sinian Dengying Formation controlled by faults are thick and distributed in rows and zones;they are reformed by contemporaneous–quasi-contemporaneous and supergene karstification jointly, forming pore-type reservoirs with a thickness of 200-400 m.(4) The two sets of source rocks enter oil generation windows from Permian to Early Triassic, and the oil migrates a short distance to the lithologic traps of mounds and shoals to form a huge scale paleo-oil reservoir group;from Late Triassic to Jurassic, the oil in the paleo-oil reservoirs is cracked into gas, laying the foundation of present natural gas reservoirs.(5) The mound-shoal body at the platform margin of Dengying Formation and the two sets of high-quality source rocks combine into several types of favorable source-reservoir combinations, which, with the advantage of near-source and high-efficiency reservoir formation, and can form large lithologic gas reservoirs. The Mianyang-Jiange area is a potential large gas field with trillion cubic meters of reserves. According to seismic prediction, the Laoguanmiao structure in this area has the Deng-2 Member mound-shoal reservoir of about 1300 km^(2), making it a ultra-deep target worthy of exploration in the near future.

Boudin Types, Their Morphology and Significance in Interpreting Deformational History in Proterozoic Rocks of North Delhi Fold Belt, North Western India

The boudins can be of symmetric as well as asymmetric type and can help in determining shear sense and help unfold the deformational history, hence are important structure for recognizing the history of deformation in an area;Once the rocks of an area undergo polyphase of deformation, the boudins get modified and can no longer help in determining the deformational evidences. The present study involves identification of various types of boudins their classification and morphology as per existing status of knowledge and their role in determining the type of deformation in Neem Ka Thana belt, Proterozoic rocks of North Delhi fold belt. The study of symmetric, asymmetric and modified boudins in the area enabled the author to deduce that the rocks in above belt have suffered a ployphase deformation marked with flattening type of progressive deformation during the first phase (DF1) of deformation and the second phase (DF2) with a time gap, has produced modified boudins and folded boudin structures with the largely same axis of deformation in both these deformations.

前陆冲断带构造分段特征——以准噶尔盆地西北缘断裂构造带为例

前陆冲断带普遍具有构造分段的特点。横断层、侧断坡与斜断坡常是构造分段的边界 ,它们起着运动方向、变形速率、构造样式与成因机制转换的作用。准噶尔西北缘前陆冲断带是古生代晚期—中生代早期发展起来的大型冲断推覆系统 ,南自车排子 ,北至夏子街、红旗坝的大型断裂带为其冲断前锋断裂。由于形成时间、活动方式与受力条件等出现变化 ,车排子—夏子街断裂带被北西向的横断层分割为构造样式与地质结构截然不同的三段 ,南段为红山嘴—车排子断裂带 ,构成车排子断隆的东部逆冲边界 ;中段为具压扭性质的克拉玛依—百口泉断裂带 ;北段为具冲断推覆性质的乌尔禾—夏子街断裂带。中生代晚期—新生代以来该前陆冲断带被稳定埋藏 。

燕山造山带燕山期构造叠加及其大地构造背景

广泛的岩浆活动和强烈的构造变形是中国东部燕山期造山作用的两个主要特征。火成岩的空间展布,特别是同构造侵入杂岩体和火山岩盆地的展布与同期变形带的走向(和构造指向)具有很强相关性。本文通过火成岩构造组合、构造形迹及岩浆-构造事件序列等的共同约束,讨论华北地区燕山板内造山带造山过程中的构造叠加、构造应力场转换及其形成的大地构造背景。研究认为,燕山地区发育的“花边状”的褶皱和被褶皱的逆冲推覆带等,是多幕挤压变形叠加的记录。早侏罗世晚期(J31 )、中侏罗世晚期(J32 )、晚侏罗世中期(J23 )、晚侏罗世晚期(J33 )和早白垩世早期(K11 )5期不同方向展布的火成岩对应方向不同的收缩构造,提出早白垩世早期(K11 )本区可能存在区域北西向挤压构造及该期华北地区总体仍处于收缩构造环境的认识。华北燕山造山带是在蒙古—鄂霍茨克构造带,上扬(斯克)—楚科奇(斯克) (Verkhoyano-Chukotsk)造山带,伊泽奈崎(Izanagi)洋俯冲带和特提斯洋俯冲带4个边界会聚大背景中形成和演化的。

祁连成矿带钨矿成矿特征及其区域找矿标志

在对祁连成矿带内钨的区域成矿地质和地球化学背景,钨及钨多金属矿床地质特征等综合分析基础上,将本区钨及钨多金属矿床初步划分为夕卡岩型、石英脉型、云英岩型以及海相火山岩型等4种类型,指出元古代及早古生代,特别是元古宙各时代的含钨中基性火山岩-碎屑岩和碳酸盐岩地层、与造山构造作用(俯冲造山和/或碰撞造山)有关具有多阶段侵入的以偏碱性和钙碱性成分为主的复式中酸性岩浆侵入体以及多组构造系统复合是本成矿带钨矿床,特别是大型钨矿床的主导控制因素。进一步总结了本区钨矿区域找矿标志。

东亚夏季风边缘带的气候特征

利用近30年的NCEP再分析格点资料及中国站点降水资料,从降水、湿度、风场、水汽输送等角度研究了东亚夏季风边缘带的气候特征及其与华北、西北降水的关系。结果表明,降水场、比湿场、风场、水汽输送场所描述的东亚夏季风边缘带位置基本一致,大致沿西南—东北走向自西向东经过黄河上游—河套—华北北部—东北。夏季风边缘带附近的夏季降水年际变化较大,且夏季降水量与季风强度呈正相关。当夏季风影响到西北、华北北部时,西北、华北夏季降水偏多;反之则偏少。

川西鲜水河断裂带三叠系如年各组放射虫硅质岩的地球化学特征

川西鲜水河断裂带三叠系如年各组放射虫硅质岩的w(SiO2)为71.16%～90.06%,w(Si)/w(Al)为49～71,表明它们含有较高比例的陆源泥质沉积物。硅质岩样品的w(Al2O3)/w(Al2O3+Fe2O3)为0.63～0.81,w(V)<23×10-6,w(V)/w(Y)<2.8,w(Ti)/w(V)>26,具有大陆边缘型硅质岩的特征。大部分样品的稀土元素w(Ce)/w(Ce*)为1.02～1.47,w(La)N/w(Ce)N为0.75～1.07,为大陆边缘型硅质岩,仅一件样品的稀土元素具有大洋盆地硅质岩的特征。对放射虫硅质岩地球化学特征以及浊积岩、玄武岩岩石组合的研究表明鲜水河断裂带在中三叠世拉丁期处于强烈裂陷阶段。

扬子地块西北缘后龙门山南华纪-早古生代沉积地层特征及其形成环境

通过对扬子地块西北缘后龙门山构造带南华纪—早古生代沉积地层的分析研究,综合运用岩石学、沉积特征分析的手段,结合与前龙门山构造带、碧口地块、米仓山构造带和汉南地块的沉积特征对比,探讨后龙门山构造带南华纪—早古生代的沉积环境,查明其形成环境。结果表明:在南华纪—早古生代后龙门山构造带沉积环境可分为南华纪—震旦纪裂解-稳定沉积和早古生代伸展裂陷沉积两个阶段,其中在早古生代伸展裂陷阶段后龙门山构造带经历了裂解→抬升→局部裂解→抬升→裂解的反复过程,最终形成了志留系茂县群裂陷槽沉积,主要沉积了一套代表伸展裂陷环境的沉积岩系,并有少量的陆内火山岩系。研究结果进一步证实,龙门山构造带在南华纪—早古生代总体是一个陆内裂谷带,不发育与古缝合线相关的构造混杂岩和蛇绿混杂岩带,是在陆内裂谷的基础上于印支期—燕山期形成的陆内造山带。

川西北地区海相油气成藏物质基础——优质烃源岩

川西海相油气勘探程度低,油气成藏条件研究薄弱。通过区域地质、烃源岩形成环境、有机地化和有机岩石学等综合研究,重点探讨了龙门山构造带北段海相优质烃源岩发育情况。龙门山北段海相油气成藏的烃源条件好,主要有筇竹寺组、大隆组优质泥质烃源岩和栖霞组、茅口组优质碳酸盐岩烃源岩,而泥盆系烃源岩分布有限,奥陶纪—志留纪缺乏优质烃源岩形成条件。该区经历过大规模油气运移、聚集成藏和后期破坏过程,分析这一过程对川西海相油气勘探具有借鉴意义。预测龙门山逆冲推覆构造带和川西坳陷深处具有良好的海相油气勘探前景。

河西经济带建设在大西北开发中的地位与作用

本文论述了建设河西经济带对开发大西北，维护社会稳定和国家统一，缩小东西部差异，减轻人口压力及发展边境贸易等方面的重大意义．

新疆博格达山分段及深浅构造转换关系

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