Mesozoic thrusts and extensional structures in the Daqingshan orogen, Inner Mongolia, and their temporal and spatial relationship

Three large-scale thrusts developed in the Daqingshan orogen, Inner Mongolia, with a northeast-east trending from Louhuashan to Suletu are described in this paper. These northwest-directed thrusts, together with the four tectonic belts (or tectonic sheets) separated by these faults, formed a typical thrusting system. The originally defined Hohhot metamorphic core complex may be a tectonic sheet, making the uppermost tectonic unit of the thrusting system and truncated by the Daqingshan detachment fault on top. The existing tectono-chronological studies showed that the thrusting of this region possibly happened at the same time as the extension along the top detachment fault. This presents that the contraction and extension in Daqingshan orogen were probably simultaneous. The structural pattern of the Daqingshan orogen can be correlated to the Himalayan orogen, and models for simultaneous thrusting and detachment in Himalaya may give a hint for explaining the development of the Daqingshan orogen.     

满洲里大青山地区火山岩岩石地球化学特征及其与铀成矿关系

大青山盆地岩区中生代火山岩碱质含量高,富SiO2和K2O,贫CaO和MgO,属于钙碱性硅饱和、过饱和型岩石类型,A12O3含量高而且稳定,富集强不相容元素、多金属元素和亲石元素,稀土总量高,轻重稀土分馏较强.火山岩浆可能源于富集不相容元素的交代型地幔,并不同程度的遭受地壳混染而形成,源岩经历了流体交代作用.结合区域构造和前人资料,认为该区中生代火山岩是岩石圈拼合以及伸展背景下地幔部分熔融的产物.通过火山岩地球化学特征、其含铀性以及和临区产铀火山岩特征类比,可知本区具较好的火山岩型铀矿床找矿前景.     

40Ar-39Ar ages of the Louzidian-Dachengzi ductile shear zone near Chifeng,Inner Mongolia and their tectonic significance

The Louzidian normal fault occurs as the eastern detachment fault of the Kalaqin metamorphic core complex. Field observations and microstructural analyses reveal that the Louzidian-Dachengzi ductile shear zone developed in its lower-plate was genetically related to sinistral strike-slips and extensional faulting. Two samples from this ductile shear zone yield 40Ar-39Ar plateau ages of 133 Ma (Bi) and 126 Ma (Kp), which are concordant with their isochron ages. The plateau age of 133 Ma (Bi) records the formation age of the ductile shear zone. The inconsistent relationship between the earlier strike-slip ductile shear zone and the later normal fault makes the Kalaqin Quasi-metamorphic core complex distinctive from Cordilleran metamorphic core complex. These ages provide important geochronological data for putting constraints on the formation age and genesis of such ductile shear zones.     

新疆若羌县赤石山变质核杂岩研究

新疆北山裂谷带西缘若羌县赤石山地区存在大型变质核杂岩构造。其下拆离盘为古元古界结晶基底杂岩 ,上拆离盘为中元古界白湖群变质岩系 ,滑脱拆离带为已变形的大型韧性正断层。核杂岩南、北侧发育上叠盆地 ,北侧形成“年轻”正断层及同构造期岩浆岩。变质核杂岩的形成与晚古生代北山陆内裂谷区域伸展有直接联系。该区变质核杂岩的首次厘定 ,对深化北山裂谷的研究具有重要意义     

Diachroneity of continental subduction and exhumation: Constraints from the Permian-Triassic HP metamorphic terrane in the Tongbai orogen, central China

High-pressure （HP） metamorphic terrane in the Tongbai orogen comprises two HP slices （I and II） and a tectonic m61ange zone in the northeast and a blueschist-greenschist zone in the southwest. HP slice I is represented by the northern and southern eclogite zones on the two sides of the Tongbaishan antiform. HP slice II is represented by retrograded eclogite-bearing metamorphic en- claves in Cretaceous gneissic granites in the Tongbai Complex. U-Pb, Lu-Hf, Rb-Sr and 4Ar/39Ar multichronometric data indi- cate that the peak metamorphism of HP slice I took place at -255 Ma, whereas the metamorphic ages of HP slice II are as young as 232-220 Ma. By contrast, the tectonic melange zone near the suture was metamorphosed at -256 Ma. Such a diachroneity of dif- ferent slices across the direction of the orogen in the Hong＇an-Dabie-Sulu HP/UHP terrane is ubiquitous, and it can be interpreted by a syn-subduction detachment/exhumation model. Furthermore, the metamorphic age of HP slice I in the Tongbai orogen is older than that of the equivalent HP slice in the Hong＇an orogen by ~15 Ma, suggesting that the diachroneity may have also ex- isted along the direction of the orogen. A seesaw-type subduction/exhumation model is proposed to explain this age disparity and the subduction of the South China Block becomimg shallower towards the west.     

1980—2015年内蒙古森林火灾的时空动态

【目的】林火是森林生态系统中重要的干扰因子,严重影响着森林的结构与功能。内蒙古大兴安岭是我国重要的森林生态系统之一,从内蒙古地区地域、海拔、火灾原因分布等可能导致火灾的时空因素分析林火灾害,为森林防火和管理提供有力的科学依据。【方法】基于遥感影像,借助ArcGIS 10.2和Origin等软件,分析了1980—2015年内蒙古地区森林火灾特点,结合时间、空间的因素,探讨林火的时空动态规律。【结果】内蒙古地区森林火灾时空上表现出规律性分布。受害森林面积年变化存在周期性规律,周期间隔16 a,且春季为林火高发季节,在进行森林防火的资源调节过程中,火灾发生次数较多的4、5月正处于春分、清明和谷雨时节,应以控制火源为主要内容。此外,月初林火发生概率相对较高,应在该时段提高警惕; 林火的发生主要集中在9:00—17:00; 多发于呼伦贝尔市、赤峰市、鄂尔多斯市和兴安盟等地区,其中兴安盟过火面积最大,大兴安岭林区火灾也比较频繁。【结论】内蒙古森林火灾频发,过火面积较大,且火灾频发与人类活动及气候特点息息相关。森林火灾主要由人为活动造成,必须严格控制野外火源、生活用火等。建议在掌握内蒙古自治区森林火灾时空动态特征的基础上,加强防火宣传与教育,并运用科学的森林防火措施,制定合理的森林防护政策。     

40Ar-39Ar ages of the Louzidian-Dachengzi ductile shear zone near Chifeng, Inner Mongolia and their tectonic significance

The Louzidian normal fault occurs as the eastern detachment fault of the Kalaqin metamorphic core complex. Field observations and microstructural analyses reveal that the Louzidian-Dachengzi ductile shear zone developed in its lower-plate was genetically related to sinistral strike-slips and extensional faulting. Two samples from this ductile shear zone yield ⁴⁰Ar-³⁹Ar plateau ages of 133 Ma (Bi) and 126 Ma (Kp), which are concordant with their isochron ages. The plateau age of 133 Ma (Bi) records the formation age of the ductile shear zone. The inconsistent relationship between the earlier strike-slip ductile shear zone and the later normal fault makes the Kalaqin Quasi-metamorphic core complex distinctive from Cordilleran metamorphic core complex. These ages provide important geochronological data for putting constraints on the formation age and genesis of such ductile shear zones.     

内蒙古白音诺铅锌矿床富锰单斜辉石与矿化的关系

内蒙古白音诺铅锌矿床是我国北方一个典型矽卡岩矿床，具有大而富的特点，矿区矽卡岩广泛发育，富锰单斜辉石矽卡岩与矿化的关系最为密切。单斜辉石主要为两期形成。早期富Ｍｇ，贫Ｆｅ，Ｍｎ的透辉石形成于较高的温度、ｆＯ２和ＰＨ条件下；晚期富Ｆｅ，Ｍｎ的锰钙铁辉石形成于较低的温底、ｆＯ２和ＰＨ条件下，后者与铅锌矿化具有密切的时空关第。成矿流体自矿区南西向北东方向流运过程中物理化学条件的改变，是造成矽卡岩矿物及矿     

Spatial and temporal evolutions of groundwater arsenic approximately along the flow path in the Hetao basin, Inner Mongolia

Patchy distribution of high As groundwater has normally been observed in As-affected areas. Spatial and temporal evolutions help in better understanding mechanisms of As mobilization and in developing effective strategies for ensuring drinking water safety. Four multilevel samplers were installed approximately along the groundwater flow path to investigate spatial and temporal variations in groundwater As in the Hetao basin, Inner Mongolia. Both water chemistry and groundwater level were monitored for about two years. Groundwater As concentration generally showed increasing trends, and Eh values showed decreasing trends along the flow path, indicating that As was mobilized via reductive dissolution of Fe oxides. However, in evaporation discharge area, shallow groundwater As was generally lower than those upstream and downstream. In addition to evaporation, siderite and pyrite precipitations controlled groundwater As concentrations. The negative correlations between As concentration and SIpyrite (or SIsiderite) implied that siderite and pyrite precipitations wold scavenge groundwater As and lower As concentration. Temporal variation showed different trends in different locations. It may reflect replenishment of high/low As groundwater for the increase/decrease in As concentrations, resulting from water level fluctuation. The increase trends in groundwater As concentrations at depth around 15m in the discharge areas would result from the increase in the recharge of underlying groundwater (20m) with high As concentration due to enhanced evaporation in the seasons with high water levels. The investigation suggested that monitoring of groundwater As should be routinely carried out to ensure the drinking water safety in the As-affected areas.     

Zircon SHRIMP U-Pb ages of the “Xinghuadukou Group” in Hanjiayuanzi and Xinlin areas and the “Zhalantun Group” in Inner Mongolia, Da Hinggan Mountains

A report is presented of SHRIMP zircon U-Pb dating data of meta-igneous and meta-sedimentary rocks of the Xinghuadukou Group(Xinlin-Hanjiayuanzi area,Heilongjiang Province)and meta-volcanic rocks of the Zhalantun Group(Zhalantun district,Inner Mongolia).The SHRIMP analyses show that the meta-igneous rocks from the Xinghuadukou Group formed at 506±10―547±46 Ma,belonging to Early-Middle Precambrian,whereas the meta-sedimentary rocks yielded detrital zircons,with ages of 1.0―1.2,1.6―1.8 and 2.5―2.6 Ga,indicative of deposition age at least<1.0 Ga. Meta-basic volcanic rocks from the Zhalantun Group have a formation age of 506±3 Ma.These data suggest that both the Xinghuadukou and Zhalantun Groups formed during Cambrian and/or Neoproterozoic time,rather than Paleoproterozoic time as previously thought.Early Precambrian inherited zircons in the meta-igneous rocks and numerous Precambrian detrital zircons in the meta-sedimentary rocks imply that these rocks were formed proximal to older crust.It is inferred that the Xinghuadukou and Zhalantun Groups represent Cambrian and/or Neoproterozoic vol- cano-sedimentary sequences formed in an active continental margin setting.     

云南省麻栗坡县某锡钨矿床成矿条件分析

云南省麻栗坡县某锡钨矿床位于滇东南南温河变质核杂岩矿聚区。在分析该矿床的地质特征基础上,分析了该矿床的成矿条件。结果表明,该矿床主要受华南褶皱系西南边缘的滇东南坳褶带,越北隆起之北缘,环老君山花岗岩体钨、锡多金属成矿带控制。     

内蒙古阿拉善左旗查干德日斯超贫磁铁矿地质、磁异常特征:对阿拉善地块火山沉积变质型铁矿资源前景的指示

矿区查干德日斯位于阿拉善地块巴音乌拉山断隆东缘。野外地质、地球物理勘探工作表明该地区存在较大规模的超贫磁铁矿,磁铁矿体TFe平均含量为14.04%(12.32%~14.98%),m Fe 6.55%(5.32%~7.47%)。该磁铁矿主要赋存于灰黑色斜长角闪片麻岩,具明显层控特点,赋矿原岩应为富铁基性火山岩建造,由区域中-深程度变质作用形成,属火山沉积变质型铁矿床。类比阿拉善地块区域磁场特征认为,阿拉善地块弱磁结晶基底中广泛分布的斜长角闪片麻岩类为寻找超贫磁铁矿提供巨大的找矿空间。     

Formation mechanisms of megadunes and lakes in the Badain Jaran Desert, Inner Mongolia

Field observations demonstrate that calc-sinters occurred in the lakes of Badain Jaran Desert. 87Sr/86Sr ratios,14C,δ 13C and mineral com-positions of calc-sinters,and 3He/4He,4He/20Ne,δ 18O,δ D,pH and TDS of water from springs and lakes are analyzed in detail. The results indicate that the lake water is supplied through deep fault zone. The “ker-nel” of stabilized dunes in the Badain Jaran Desert perhaps consists of calc-sinters and calcareous ce-mentation layers. Deep-seated groundwater effuses from this “kernel” and recharges to lakes in desert. Precipitation and snowmelt water from the Qing-hai-Tibet Plateau is fed into the Badain Jaran Desert,Gurinai,Wentougaole and Ejinqi areas through the Xigaze-Langshan Fault zone. The isotopic composi-tions of groundwater in the Alax Plateau are abnor-mal due to the strong evaporation of the Gyaring and Ngoring lake water in the headstream of the Yellow River. Groundwater dissolves dissoluble fractions of rocks during its transportation through the fault zone and flows out of the mouth of spring in the Badan Jaran Desert. The dissoluble fractions are finally de-veloped into calc-sinters and calcareous cementation layers around the spring. Calci-sinters are gradually largened and eventually emerge on the surface of lake water. Eolian sands accumulate on the surfaces of calc-sinters and calcareous cementation layers,and eventually develop into dunes. Invasion of magma causes an increase in the temperature of groundwater within the faults. Groundwater evapora-tion provides water vapor for the formation of humid stabilized dunes during its upwelling. Rhizoconcre-tions found in Yihejigede indicate that the dune was formed and remained immovable 4700 years ago. The height of the megadunes is proportional to thermal quantity carried by the groundwater.     

内蒙古乌拉特中旗温更辉长岩类的岩石学、地球化学特征及其构造意义

内蒙古乌拉特中旗温更地区发育了一套由角闪辉长岩和橄榄辉长岩组成的混杂堆晶岩系,主要造岩矿物为橄榄石、辉石、斜长石及角闪石等。电子探针数据分析表明,角闪辉长岩中的辉石为透辉石区,而斜长石An平均为86,属倍长石。这些岩石表现为大离子亲石元素（LILE）K,Rb,Sr,Ba明显富集,高场强元素（HFSE）Nb,Ta,Zr相对亏损。根据Al₂-TiO₂,Wo-En-Fs以及An-Mg′图解,结合其微量元素地球化学特征可以判断角闪辉长岩类形成于岛弧环境。橄榄辉长岩中橄榄石Fo平均为74,属贵橄榄石,斜长石An平均为80,属倍长石,辉石全部落入顽辉石区。这些岩石表现了贫SiO₂高MgO,富集大离子亲石元素K,Rb,Sr,Ba和轻稀土（LREE）,个别高场强元素Nb亏损,兼具大洋中脊与岛弧的特征。根据Wo-En-Fs以及An-En图解推测橄榄辉长岩产于弧后盆地环境。温更混杂辉长岩的形成与古亚洲洋板块的俯冲消减作用有关,是研究古亚洲洋演化历史的一个重要岩石学标志。     

浑善达克沙地草地景观要素空间分布关系及其格局分析

采用以2×2联列表为基础的X2检验、Ochiai指数和孔隙度指数,对浑善达克沙地中的沙丘、草本植被、榆树(Ulmuspumila)和风蚀坑的空间分布关系及格局进行了分析.X2检验结果显示榆树、沙丘、风蚀坑三者在分布上相互之间存在极显著的正关联关系,草本植被的分布分别与榆树、沙丘、风蚀坑的分布之间存在极其显著的负关联关系.这表明榆树对当地沙丘的形成和固定起主要作用.孔隙度分析结果表明,四种景观要素具有偏离随机适度聚集的空间格局.     

Emplacement age and tectonic implications of the Xilinhot A-type granite in Inner Mongolia,China

A new rock type of granite, approximate 45 km^2 in area and located about I0 km south of Xilinhot, Inner Mongolia, was found in the Sunitezuoqi (or called Suzuoqi)-Xilinhot tectonic belt and identified as an A-type miarolitic intrusion. The pluton has miarolitic structure and is composed chiefly of perthite, quartz, euhedral albite and potassium feldspar. Various types of textures occur in the pluton, such as perthitie, graphic and myrmekite textures. Only quartz is found in miarolitic cavity. This A-type granite with seagull-shaped REE patterns and obvious negative Eu anomaly (δEu=0.24--0.28) is high in SiO2 (76%--77%), K and Na (Na2O K2O=7.75%--8.15%) and low in Ca(CaO=0.20%--0.22%), Fe and Mg. Both petrographical observations and chemical compositions indicate that it is an A-type granite. Zircon SHRIMP U-Pb analyses indicate that this A-type granite was emplaced at 276 2 Ma and coeval with the same type of granites in the adjacent areas. Therefore, it suggests that this pluton was likely formed in a post-orogenic extensional setting and probably related to break-off of subducted slabs in Central Asian Orogenic Belt (CAOB), which indicate that the Sunitezuoqi-Xilinhot belt was tectonically evolved into post-orogenic stage since early Permian.     

内蒙古兴安盟羊狂蝇蛆病原流行病学与季节动态研究

1999年3月－2000年2月，对来自内蒙古兴安盟牧区、半农半牧区和农区的5个旗县市22个乡（苏木、镇）的216只羊进行了尸体剖检，共收集羊狂蝇1龄、2龄和3龄幼虫3926个；对3群552只羊进行了临床检验。结果表明：羊狂蝇（Oestrus ovis)蛆是引起兴安盟羊狂蝇蛆病的病原；临床检查，羊狂蝇蛆病感染率为92.21%；尸体剖检，羊狂蝇各龄幼虫在羊鼻腔内全年至少寄生8个月，由于重复感染各龄幼虫感染率随季节不同而不同，范围在40.00%-95.00%之间，感染强度为1－140个；动态监测为羊狂蝇1、2、3龄幼虫全年均表现出两个感染高峰，分别为6月和11月、5月和翌年1月、5月和8月，从而说明兴安盟羊狂蝇繁殖有两个世代。     

Zircon LA-ICPMS study and petrogenesis simulation of Dahuabei pluton in the Wulashan area,Inner Mongolia

Dahuabei pluton in the Wulashan area,Inner Mongolia,is an alkaline and peraluminous granitic pluton.LA-ICPMS U-Pb dating of zircons indicates that this pluton crystallized at 330±10 Myr.The pluton did not experience apparent zircon fractionation.The consistent temperatures between Zr saturation (765℃) and the average zircon-rutile Ti equilibrium (780℃),together with zircon ages and their CL images,indicated that there were no inherited zircons in this pluton.Through the simulation of the dry-system crystallization process of magma cooling at 200 MPa and 1100-709℃,the phase diagram and composition evolution tendency of different phases were obtained.The magma reached its liquidus at 1069℃.Sanidine was the first crystallized phase;at 709℃ the residual magma was less than 4%,and the range of 1069-719℃ should be the most suitable approach to the real condition.It is shown that at least some part of the pluton underwent such isobaric equilibrium crystallization processes during its crystallization.     

粤西大降坪黄铁矿矿床He-Ar同位素和稀土元素组成及成矿物质来源探讨

对大降坪黄铁矿床的Ⅲ、Ⅳ号矿体样品进行了流体包裹体的He-Ar同位素测定,3He/4He值在0.13~2.55 Ra之间,40Ar/36Ar在348~443之间,反映出成矿流体中有地幔流体的侵入,可能是深源地幔的热液沿着大降坪黄铁矿床的逆冲断层进入矿体,对矿体进行了热液改造,分化出Ⅲ号条带状矿体和Ⅳ块状矿体两个不同形态的矿石类型;矿石和围岩的稀土元素的研究结果表明,Ⅲ号矿体和近Ⅲ号矿体围岩及边坡围岩的稀土元素分配曲线基本一致,均表现为铕负异常(δEu=0.52~0.83),而Ⅳ号块状矿体及近Ⅳ号矿体围岩表现为铕正异常(δEu=1.03~14.70),可能是受到地幔热液的影响而热液蚀变改造引起的.