Geochemical Characteristics and Genesis of Late Cretaceous to Paleogene Basalts in the Tuyon Basin, South Tianshan Mountains

1. Introduction The Tianshan Mountains is a typical intercontinental orogenic belt in the world. From late Carboniferous to Permian, the old Tianshan formed during the tectonic amalgamation of the Tarim block, Tianshan block and Siberia craton (Carroll et al, 1990). Mid-Cenozoic basalts are widely distributed in both the Tuyon basin of southwest Tianshan and its western part of Tianshan in Jierjisi in late Cretaceous-Paleogene period, which indicates the activation of the old Tianshan.…     

Geochronology and Geochemistry of the Radiolarian Cherts of the Mada’er Area, Southwestern Tianshan: Implications for Depositional Environment

In the Southwestern Tianshan, the geologic ages of many strata and their depositional environments are still poorly constrained because of complex structures. The Mada’er area is located in the Kuokesaleling belt, Southwestern Tianshan. The cherts from the former Wupata’erkan Group contain abundant radiolarian fossils, including 10 species which are identified as late Devonian to early Carboniferous in age. Eleven chert samples have SiO2 contents ranging from 88.80 wt% to 93.28 wt%, and 2.02 wt% to 3.72 wt% for Al2O3. The SiO2/Al2O3 ratios of all samples vary from 23.84 to 46.11, much lower than those of the pure cherts (80–1400). These values suggest that the cherts contain high ratios of terrigenous materials. The Al2O3/(Al2O3+Fe2O3) ratios vary between 0.64 and 0.77, whereas V and Cu concentrations range from 10.92 ppm to 26.7 ppm and from 2.15 ppm to 34.1 ppm respectively. The Ti/V ratios vary from 25.53 to 44.93. The total REE concentrations of the cherts are between 30.78 ppm and 59.26 ppm, averaging 45.46 ppm. The (La/Ce)N ratios range from 0.81 to 1.12, and 0.88–1.33 for (La/Yb)N, averaging 1.09, which suggests a continental margin environment. Consequently, it is inferred that the cherts formed in a residual sea environment during the late Devonian to early Carboniferous time, which suggests that the collision between the Karakum-Tarim and Kazakhstan-Junggar plates did not occur at the time. In addition, the regional geological information indicates that the study area experienced a post-collision stage during the early Permian, and thus it is likely that the collision between the two plates took place in the late Carboniferous.     

Geochemical Characteristics of Granitoids in the Eastern Sector of the Northern Tianshan Mountains in Xinjiang

The granitioids in question are located in the geosynclinal fold belt of the Northern Tianshan Mountains.The magmas are intruded into a Carboniferous marine volcanic-sedimentary rock series. forming a contempo-raneous. intermediate-basic to acid. composite intrusion. With a whole-rock Rb-Sr isochron age of 315.7 Ma. itis considered to be of middle Heicynian age. The granitoids have a SiO_2 content of 48-78%, a calc-alkali indexof 60 and silica-alkali indices ρ=2.2-2.4 and σ=1.5-2. From basic to acid compositions, the total REE con-tent increases from 38 to 143 ppm. δEu ranges from 0.47 to 0.86 and the Eu anomalies are negative. Thenormalized curves of REE of various rock types are very similar. These coupled with the characteristics of traceelement geochemistry show that the intrusion is an island arc-continental margin, calc-alkaline one. Theδ~(18)O values range from 5.8 to 8.9‰ and the ~(87)Sr/~(86)Sr initial ratio is 0.705. The materials of the intrusion arecomposed of a mixture of the magmas at the top of the upper mantle and in the lower crust, This indicates thatthe rocks might be consanguineous. differentiated and evolved products and possess the characteristics of Ⅰtype granites.     

Geochemical characteristics of crude oils from Well Zheng-1 in the Junggar Basin, Xinjiang, China

Well Zheng-1 is located in the combined area of the central uplift and the north Tianshan piedmont depression in the Junggar Basin. Two oil-bearing beds are recognized at 4788–4797 m of the Lower Cretaceous Tugulu Formation (K1tg) and 4808.5–4812.5 m of the Lower Jurassic Sangonghe Formation (J1s). The geochemical characteristics of family composition, carbon isotopic composition, saturated hydrocarbons, sterane and terpane biomarkers and carotane of two crude oils are described in this paper. The results show that the geochemical characteristics of the two crude oils are basically similar to each other, indicating they were all derived mainly from the high mature, brine, algae-rich lake facies sediments. Oil-source correlation revealed that crude oils of the two beds were derived mainly from the source rocks of Permian and mixed by the oil derived from the source rocks of Jurassic and Triassic. This is consistent with the geological background with several sets of source rocks in the area studied.     

Characteristics of the Mesozoic and Cenozoic Tectonic Stress Fields of the Urumqi-Usu Region, Xinjiang

Based on the study of folds and related conjugate shear joints, the tectonic stress fields of the Urumqi-Usu region to the north of the North Tianshan Mountains have been reconstructed. Furthermore the author discussed the tectonic movements and their dynamic features. The early tectonic movement in the investigated region occurred from the end of the Late Jurassic to the initial stage of the Early Cretaceous, with the maximum (tensile) and minimum (compressional) principal stress trajectories in the tectonic stress field being in E-W and S-N directions respectively; the late tectogenesis took place from the end of the Early Pleistocene to the initial Middle Pleistocene, with the maximum and minimum principal stress trajectories in the late stress field striking in WNW and NE-NNE directions respectively. Through computer-aided simulated calculation by the finite element method and analysis of geological structure, it has been ascertained that the early tectogenesis is a nearly N-S compressive movement and the late one a NE to nearly N-S compressive movement with reverse shear. The dynamic force which caused the tectogeneses came from the movement of the southern major fault, i.e. the North Tianshan Mountains.     

Occurrence of the Iron–rich Melt in the Heijianshan Iron Deposit, Eastern Tianshan, NW China: Insights into the Origin of Volcanic Rock–hosted Iron Deposits

Long-standing controversy persists over the presence and role of iron–rich melts in the formation of volcanic rock-hosted iron deposits. Conjugate iron–rich and silica–rich melt inclusions observed in thin-sections are considered as direct evidence for the presence of iron-rich melt, yet unequivocal outcrop-scale evidence of iron-rich melts are still lacking in volcanic rock-hosted iron deposits. Submarine volcanic rock-hosted iron deposits, which are mainly distributed in the western and eastern Tianshan Mountains in Xinjiang, are important resources of iron ores in China, but it remains unclear whether iron-rich melts have played a role in the mineralization of such iron ores. In this study, we observed abundant iron-rich agglomerates in the brecciated andesite lava of the Heijianshan submarine volcanic rock–hosted iron deposit, Eastern Tianshan, China. The iron-rich agglomerates occur as irregular and angular masses filling fractures of the host brecciated andesite lava. They show concentric potassic alteration with silicification or epidotization rims, indicative of their formation after the wall rocks. The iron-rich agglomerates have porphyritic and hyalopilitic textures, and locally display chilled margins in the contact zone with the host rocks. These features cannot be explained by hydrothermal replacement of wall rocks(brecciated andesite lava) which is free of vesicle and amygdale, rather they indicate direct crystallization of the iron-rich agglomerates from iron-rich melts. We propose that the iron-rich agglomerates were formed by open-space filling of volatile-rich iron-rich melt in fractures of the brecciated andesite lava. The iron-rich agglomerates are compositionally similar to the wall-rock brecciated andesite lava, but have much larger variation. Based on mineral assemblages, the iron-rich agglomerates are subdivided into five types, i.e., albite-magnetite type, albite-K-feldsparmagnetite type, K-feldspar–magnetite type, epidote-magnetite type and quartz-magnetite type, representing that products formed at different stages during the evolution of a magmatic-hydrothermal system. The albite-magnetite type represents the earliest crystallization product from a residual ironrich melt; the albite-K-feldspar-magnetite and K-feldspar-magnetite types show features of magmatichydrothermal transition, whereas the epidote-magnetite and quartz-magnetite types represent products of hydrothermal alteration. The occurrence of iron-rich agglomerates provides macroscopic evidence for the presence of iron-rich melts in the mineralization of the Heijianshan iron deposit. It also indicates that iron mineralization of submarine volcanic rock-hosted iron deposits is genetically related to hydrothermal fluids derived from iron-rich melts.     

Laumontitization as an Exploration Indicator of Epithermal Gold Deposits： A Case Study of the Axi and Other Epithermal Systems in West Tianshan, China

In the light of field investigation, microscopic study, X-ray phase analysis and mineral infrared spectral analysis, it is considered that laumontitization is of extensive occurrence in the Axi gold orefield. The development of laumontitization and its relationship to mineralization show that the laumontitization appeared mainly at the top of and in the periphery of orebodies, and occurred at the edge of the epithermal system or at the late stage of epithermal system evolution. Therefore, laumontitization can be used as an exploration indicator of epithermal gold deposits. The fluids responsible for laumontitization in the Axi gold orefield are similar to those producing hot spring-type gold deposits or those from modem geothermal fields. Epithermal mineralization of the Axi gold deposit was dated at Carboniferous, indicating that the West Tianshan of China is a region favorable to epithermal-type gold mineralization and preservation. Hence the West Tianshan of China is a target area for exploring epithermal gold deposits.     

中国天山地区花岗岩类的基本特征

Since libration large-scale geological surveys have been made, revealing that the socalled “Tianshan granites” are a complex po]ycycle system of magmatic rocks. It consists mainly of the products of magmatic activities which took place in the differentstages of the Sangyang-Laliang cycle, the Caledonian cycle, the Hercynian cycle, the Indosinian-Yanshan cycle and the Himalaya cycle. The substantial part is composed of granodiorites and biotite granites in the Hercynian cycle. This paper provides a comprehensive discussion for the first time on the granitoid rocks of the Tianshan system in China. The architectonic element of this area consists of the entire Tianshan fold system within the territory of China, and parts of the Kalpin fault block and the Kuluktag fault block which are located in tbe border area in the north of the Tarim Basin. Morever, the petrology and geochemistry of granitoid rocks of different ages in this region are discussed as well. In conjunction with the development of the Tianshan gcosyncline, discussions also are made on the cvolution and the history of tectonic displacement of those granitoid rocks. The comparison between the granitoid rocks of different ages in respect to .their distribution patterns,petrological features, geochemistry, accessory minerals and minerogenetic specificity strongly shows that the evolution of Tianshan granitoid rocks is characterized as being from basic through acid to alkaline.     

Geochemical Features of the Two Early Paleozoic Ophiolitic Zones and Volcanic Rocks in the Central —Southern Tianshan Region ,Xinjiang

This paper deals with the geochemical features of the two Early Paleozoic ophiolite zones in the central-southem Tianshan region and the central Tianshan igneous rock belt between them.Study results suggest that the central Tianshan belt was an Ordovician volcanic arc with an affinity of continental crust, and the Kumux-Hongluhe ophiolitic zone that is located on the southern margin of central Tianshan has a crustal affinity to back-arc marginal sea.The Aqqikkudug-Weiya ophiolitic zone is an accretionary boundary between the Tuha continental block and the central Tianshan volcanic arc during Late Silurian to Devoniann;Ordovician ophi-olitic blocks,Silurian flysch sequence and HP metamorphic rock relics are distributed along the Aqqikkudug-Weiya zone.Geochemically,ophiolitic rocks in the Aqqikkudug-Weiya zone have an affinity to oceanic crust,reflecting a tectonic setting of paleo-trench or subduction zone .The Early Carboniferous red molasses were deposited unconformably on the pre-Carboniferous meta-mrophosed and ductile sheared volcanic and flysch rocks,providing an upper limit age of the central and southern Tianshan belts.     

Provenance of the Early–Middle Devonian Shugouzi Formation in the Quruqtagh, Northeastern Xinjiang: Constraints from Sandstone Geochemistry and Heavy Mineral Analysis

The Early-Middle Devonian Shugouzi Formation in the Quruqtagh block consists mainly of clastic rocks.However,their provenance has been scarcely studied since it was named.Geochemistry of clastic rocks was commonly used to interpret the provenance.Detrital heavy mineral analyses help frame the U-Pb age from zircon grains,integrated with geochemical data from detrital tourmaline and spinels.These techniques were used to characterize components of the sediment flux and define erosion areas in the Qurugtagh block,further providing evidence about the tectonic evolution of the South Tianshan and Tarim plate.The maximum depositional age constrained by detrital zircon dating was Early-Middle Devonian.Multiple diagrams for sedimentary provenance using major and trace elements indicate that continental island arc-related felsic rocks were the major source rocks for the Shugouzi Formation.Detrital tourmalines are dravite and schorl.The results of detrital tourmaline electron probe microanalysis(EPMA)show that the source rocks are mainly metasedimentary rocks and granitoids.The detrital chromian spinels within the sediments are characterized by high chroumium(Cr^#)and varying magnesium(Mg^#).The discrimination plots reveal that these spinels were sourced from island arc magmatic rocks.The laser ablation inductively-coupled plasma mass spectrometry(LA-ICP-MS)U-Pb chronology of detrital zircons suggests that the sediments were derived mainly from 414-491 Ma and 744-996 Ma magmatic rocks.Paleocurrent restoration,sandstone geochemistry,EPMA,and detrital zircon geochronology indicate that the source rocks were predominantly derived from Late Ordovician and Devonian magmatic rocks and subordinately from recycled Neoproterozoic magmatic rocks.Comprehensive analyses of the source areas suggest that a remnant arc still existed in the Early Devonian and the Shugouzi Formation was deposited in a passive continental margin.     

青藏高原隆升对新疆天山山脉地壳-上地幔构造的影响

依据地震层析和接收函数的结果获得了天山山脉东段和西段的深部构造的速度图像,探讨了印度板块向北推进和青藏高原隆升对天山山脉造山作用的影响以及天山山脉不同地段的地壳上地幔构造的差异。克拉玛依—库车剖面上清楚地展示出,天山是由高速和低速的地体拼合而成。来自塔里木的高速体向北俯冲到天山达200km以下的深度,而来自准噶尔盆地的高速体则没有明显地向南推进,说明由南向北的推进是很强的,它是造成天山山脉继续隆升的主要动力,从而造就了天山山脉。天山山脉在Moho面以上的部分是中天山北缘断裂和中天山南缘断裂之间的低速体与两侧的高速体拼合成的,其南北宽度约350km,向深度延伸越过200km。塔里木盆地和准噶尔盆地均为高速体的范围,天山山脉东段Moho面以上的地壳部分,南部高速体有向北推进和俯冲的特征,但不明显。夹在两盆地之间的天山主要为低速体,仅在乌鲁木齐和北天山山前断裂以南有残留的高速体,深度不超过30km,这表明天山是由速度不同的地质体挤压而拼合成的。天山延伸到乌鲁木齐以东,向深部的延伸仅仅100km上下。在富蕴—库尔勒剖面上,塔里木板块向北的推进相对于克拉玛依—库车剖面有所减弱。天山西段表现出强烈的造山作用,向东逐步减缓,到达天山的东段,虽然天山深部的构造活动仍然在继续进行,地震活动频繁,可是,活动区域集中在天山底部不过100km上下。说明山根的范围比西部减少了近一半。     

中新生代南北天山差异性抬升历史的磷灰石裂变径迹证据

堆积于天山山前坳陷内部的巨厚新生代地层不仅记录所在沉积区的热历史信息,还记录了物源区的信息。本文选择天山南北两侧山前坳陷中3条地质剖面进行了大量的磷灰石裂变径迹测试和部分样品的热历史模拟分析,来揭示上新世以来天山在南北方向上隆升过程的差异性。采样剖面的选取较前人更加靠近前陆盆地方向,样品所在地层年代更新。结果显示,东秋里塔格背斜剖面中的样品记录了中天山、南天山和背斜区分别在55~65Ma、20~25Ma和5Ma经历了构造隆升。玛纳斯背斜剖面中的样品记录了北天山的三次构造隆升事件分别发生于55~65Ma、20~25Ma和5Ma,其中距今5Ma为玛纳斯背斜带起始隆升的时代。结合前人在相同区域的研究成果,分析得出天山的不同部分经历了不同的构造演化历史,自150Ma以来经历了三期差异性隆升。中生代时期(150~125Ma)表现为山体整体抬升,中生代晚期-新生代早期(100~50Ma)北天山明显早于南天山开始构造隆升,新生代以来(~50Ma)的构造运动以向前陆盆地方向扩展为特征,而隆升起始时间南北差异变小。虽然在南北方向上天山山体隆起时间上存在明显的差异,但是中新生代以来山体物源区的剥蚀速率大体相同。因此,隆升起始时间与隆升量之间并不存在必然的定量关系。天山的不同块体具有不同的构造演化历史的事实提示在研究大范围构造隆升作用时,应将构造作用作为一个过程来对待。变形在传递的过程中,在时间和空间上存在一定的滞后现象。     

塔里木盆地与南天山的耦合关系:来自(U-Th)/He年龄的新证据

塔里木盆地与南天山构造-沉积耦合关系是目前国内地质研究的热点之一。文中首次利用盆地内钻井样品的磷灰石和锆石(U-Th)/He年龄探讨了塔里木盆地与南天山构造-沉积耦合关系。塔北隆起He年龄为15～3Ma的磷灰石和锆石来自于南天山,热史模拟结果揭示了南天山在晚中新世开始快速抬升的时间约为15Ma,一直持续到5Ma左右。在此基础上,建立了南天山与塔里木盆地北缘新近纪的构造-沉积耦合关系演化模式。晚中新世,南天山开始快速隆升遭受剥蚀,而塔里木盆地北缘剧烈沉降接受来自南天山的沉积物。盆地内的磷灰石和锆石He年龄有效地记录了这些地质信息,为盆-山耦合关系研究提供了新证据。     

Topographic evolution of the Tianshan Mountains and their relation to the Junggar and Turpan Basins,Central Asia,from the Permian to the Neogene

The modern Tianshan Mountains and their surrounding basins have mainly been shaped by the far field effects of the Cenozoic India-Asia collision. However, precollision topographic evolution of the Tianshan Mountains and its impacts on the Junggar and Turpan Basins remain unclear due to the scarcity of data. Detrital zircon U-Pb dating of 14 new and 23 published samples from Permian to Neogene strata in the northern Western Tianshan Mountains, northern and southern Bogda Mountains and Central Turpan Basin, are combined with sedimentary characteristics (lithofacies, petrofacies and paleocurrent data) to investigate the temporal and spatial changes in sediment provenances. Based on the age characteristics of the source rocks in the Tianshan Mountains, the detrital zircons are divided into three groups: pre-Carboniferous zircons, mainly from the Central Tianshan Mountains; Carboniferous to Permian zircons, mainly from the North Tianshan and Bogda Mountains; and Mesozoic zircons, mainly from syn-depositional volcanic activity. The topographic evolution of the Tianshan Mountains and their relation to the Junggar and Turpan Basins can be generally divided into six stages. (1) Positive-relief Tianshan and Bogda Mountains and a rifted marine basin formed during the Early Permian to early Middle Permian following late Carboniferous orogenesis, as evidenced by interbedded alluvial fan conglomerates and postcollisional extension-related volcanic rocks along the basin margins, by marine deposits far from the basin margins and by the predominance of Carboniferous to Permian detrital zircons. (2) Fluvial to lacustrine deposits in the modern southern Junggar and Turpan Basins are characterized by abundant pre-Carboniferous zircons and consistently northward-flowing paleocurrents, indicating the submergence of the Bogda Mountains and a contiguous Junggar-Turpan continental depression basin during the late Middle Permian to the Triassic. (3) The Bogda Mountains began to uplift in the Early Jurassic, resulting in opposing paleocurrent directions, a sudden increase in sedimentary lithic detritus and the dominance of Carboniferous to Permian detrital zircons along the southern and northern margins of this range. (4) In contrast to the uplift of the Bogda Mountains, the other parts of the Tianshan Mountains experienced gradual peneplanation from the Early Jurassic to the Middle Jurassic, as confirmed by widespread fluvial to lacustrine deposits, even inside the modern Tianshan Mountains, and by the dominance of pre-Carboniferous detrital zircons. (5) The dominance of Carboniferous to Permian zircons in the southern Junggar Basin suggests the West Tianshan Mountains were uplifted during the Late Jurassic, while the dominance of pre-Carboniferous zircons in the Central Turpan Basin indicates continuous peneplanation in the Eastern Tianshan Mountains. (6) The initial shape of the Tianshan Mountains-Junggar Basin-Turpan Basin system was constructed in the Late Jurassic but was modified in the Cenozoic by the India-Asia collision, resulting in much higher Western Tianshan and Bogda Mountains, low Eastern Tianshan Mountains and well-developed foreland basins. These Cenozoic changes were recorded by the rapid cooling of apatites, the dominance of Carboniferous to Permian zircons in the southern Junggar Basin and northern Turpan Basin, and the dominance of pre-Carboniferous zircons in the Central Turpan Basin.     

天山南北缘前陆冲断构造对比研究及其油气藏形成的构造控制因素分析

天山南北缘分别发育了库车前陆冲断带和乌鲁木齐前陆冲断带,南缘前陆冲断带发育4排褶皱冲断构造,北缘前陆冲断带发育3排褶皱冲断构造。天山南北缘前陆冲断构造形成时间的对比研究表明,南缘第一排构造带起始时间为23.3Ma,构造形变从山前由北向南依次展开;北缘第一排构造带的形成时限为10~8Ma,构造形变从山前开始由南向北依次展开。平衡剖面研究表明,天山南北缘地壳缩短率也存在明显差异,南缘前陆冲断带地壳缩短率为31%~59%,北缘前陆冲断带地壳缩短率为15.13%~23.74%,南缘构造缩短量要大于北缘,这种差异正是印度板块和欧亚板块碰撞的远距离构造效应从南向北传播造成的,也真实反映了天山的陆内造山过程。目前天山南缘前陆变形构造中已经发现几个规模较大的油气田,北缘虽有多处油气显示和油气田的发现,但数量和规模均较南缘少和小。天山南北缘生储盖等石油地质条件基本相似,大型油气藏形成的差异可能主要是由天山南北缘前陆冲断带启动时间的不同造成的。     

天山山脉剥露程度与矿产保存关系初探

成矿后含矿地质体的剥露程度与矿体的保存关系是矿床学研究的疑难问题之一.利用中酸性侵入岩体的出露程度, 结合磷灰石裂变径迹测试结果及现今发现的矿产展布特征, 探讨天山山脉剥露程度与内生金属矿产保存之间的关系, 进而为区域找矿提供理论指导.统计结果表明, 北天山西段的依连哈比尕尔山、中段的博格达山和西南天山山脉皆缺乏大面积分布的深成侵入岩, 已经发现的内生金属矿产较少, 且以中低温的矿床为主; 北天山南部的觉罗塔格地区、中天山和南天山东段都大面积出露中酸性岩体, 已经发现了大量大型-超大型规模内生金属矿床, 以中高温成矿为特征; 综合分析已有的磷灰石裂变径迹测年结果统计显示, 北天山西段的依连哈比尕山、中段的博格达山和西南天山中生代晚期开始隆升, 新生代25 Ma以来隆升强烈; 北天山南部、中天山以及南天山东段山脉从侏罗纪早期就已经开始隆升而接受剥蚀, 新生代隆升较弱.结合现今山脉的地质背景、内生金属矿产展布特征、山脉隆升时间及其现今地貌特征推测, 北天山西段的依连哈比尕山、中段的博格达山和西南天山山脉由于剥蚀时间短, 因而其剥蚀程度相对较低, 地表仍出露表壳的沉积-火山岩系, 以中酸性侵入岩体为代表的深成岩体由于剥蚀量不够而还没有出露于地表, 地表出露低温的内生金属矿产; 北天山南部、中天山以及南天山东段山脉开始隆升时间早, 新生代隆升弱, 因而总体上剥蚀量、剥蚀程度大, 表壳岩系已经剥蚀殆尽, 广泛出露深成侵入岩体, 与中酸性岩体侵位有关的中高温矿产广泛展布.为此, 进一步指出了在天山山脉不同构造分区内应该着重寻找不同类型、不同成矿温度的内生金属矿产, 推测西南天山具有较好的找矿远景空间, 并认为山体剥露程度的差异是造成所谓"大矿不过国界"的主要原因之一.      

库车坳陷三叠系碎屑重矿物成分及其物源属性

库车坳陷三叠系发育良好,出露齐全,主要由陆相碎屑岩组成。本文运用电子探针微区成分分析方法,对库车坳陷北部三叠系砂岩中石榴石、电气石、铬尖晶石进行了矿物化学成分分析。结果显示,碎屑石榴石主要富含铁铝榴石,其次为镁铝榴石、锰铝榴石,钙铝榴石含量较低,他们主要来自于低级-高级变质岩和花岗岩;电气石主要来自于变质沉积岩和花岗岩;铬尖晶石则主要源自岛弧玄武岩、洋岛玄武岩和与俯冲相关的橄榄岩。综合石榴石与电气石研究结果表明,上三叠统碎屑物质更多的来自于高级变质岩和花岗岩,而下三叠统碎屑物质主要源自低级变质岩和花岗岩。通过对比西天山榴辉岩、片麻岩中石榴石成分,本文所研究的高镁石榴石以低钙铝榴石含量与榴辉岩中石榴石相区别,而与片麻岩中石榴石成分相似。西天山榴辉岩在三叠纪时期可能尚未剥露至地表,但片麻岩已有相当范围的出露。上三叠统的碎屑铬尖晶石可能主要来自于中天山及南天山的岛弧岩浆岩及蛇绿岩,部分源自洋岛玄武岩,为南天山为多岛海造山提供了沉积学证据。     

Differential uplift of the Chinese Tianshan since the Cretaceous: constraints from sedimentary petrography and apatite fission-track dating

The Chinese Tianshan is one of the important international natural laboratories for studying continental geodynamics, but its uplift time, kinematics and mechanism of formation are key unresolved questions. In order to constrain the timing, kinematics and mechanism of uplift of the Chinese Tianshan, we applied sedimentary petrography and apatite fission-track dating to Cretaceous-Tertiary series from the northern Tarim Basin and the Tianshan Mountains. We collected and analyzed 79 sandstone samples and 75 detrital heavy mineral samples from the Kezilenuer-Kuqa profile (northern Tarim Basin) with a well-defined magnetostratigraphy. Our data indicate that detrital mineral maturity abruptly decreased at the disconformity between the Upper and Lower Cretaceous, and decreased again after 15(−12) Ma. The sediments in the northern Tarim Basin changed their provenance at 124 Ma, 26(−24) Ma and 15(−12) Ma, respectively. In addition, we collected and analyzed 36 primary apatite samples from the South, Central and North Tianshan. Our results show that the Chinese Tianshan underwent three phases of differential uplift. The first phase of uplift started at the southern Central Tianshan during the Early Cretaceous and propagated southward. The second phase of uplift started at the northern Central Tianshan during the Late Cretaceous and propagated also southward. The third phase of uplift started at the northern Central Tianshan during the Eocene and propagated both northward and southward. These differential uplifts have caused development of disconformity and drops in mineral maturity of detrital sediments in the northern Tarim Basin. Such a differential and heterogeneous uplift process might have been trigged by collisions of different microcontinents (i.e., Lhasa, Kohistan-Dras and India) at the southern margin of Asia. These collisions reactivated the South Tianshan Fault and then the North Tianshan Suture, and uplifted the Chinese Tianshan step by step.     

中天山地块南北两缘的韧性剪切带

本文详细描述了天山中段沿乌鲁木齐—库尔勒公路后峡—乌瓦门段的构造变形特点。综合室内外观察研究结果，在中天山地块南、北缘，及内部的乌拉斯台地区鉴别出三条规模较大的韧性剪切带：中天山北缘剪切带前人已有研究，出露宽达10km的右行斜冲剪切带，见大量糜棱岩、超糜棱岩；乌拉斯台剪切带中的糜棱岩宽超过200m，具有左行走滑运动特点；中天山地块南缘剪切带宽度达5km，内部发育大量闪长质糜棱岩、超糜棱岩，运动方式为左行斜冲。中天山块体南北两侧的脆性边界断层与糜棱岩带变形中心基本重合。这些剪切带具有相当大的走滑位移量，指示天山各地质单元间目前的空间关系可能是走滑拼接的结果。研究天山造山带内剪切带的展布、运动方式、总变形量，对于恢复各地质单元的初始位置、了解造山动力学过程具有重要意义。     

塔里木盆地西北缘与南天山早-中二叠世盆山耦合特征

通过对塔里木盆地西北缘及相邻南天山造山带的早-中二叠世岩相古地理、构造和岩浆作用的分析表明,塔里木盆地西北缘在早-中二叠世由于地幔柱作用而导致玄武质岩浆活动,南天山造山带内部则发育几乎同时代的碰撞后花岗岩.盆山结合部位早-中二叠世的沉积中心处于不断沉降的状态,而且沉积中心逐渐向塔里木地块之上迁移.南天山在早-中二叠世碰撞后伸展背景下的隆升作用导致塔里木岩石圈向南天山之下发生陆内俯冲作用,在山前形成类似周缘前陆盆地的构造环境,山前沉积中心相当于周缘前陆盆地系统的前渊相带.塔里木盆地内部早二叠世的地幔柱活动与南天山的碰撞后伸展作用没有明显的相关关系,但是南天山在早-中二叠世的碰撞后伸展作用则与塔里木盆地西北缘的沉积-构造作用具有良好耦合关系.