Structural and stratigraphical constraints on the kinematics history of the Southern Tan–Lu Fault Zone during the Mesozoic Anhui Province, China

The Tan–Lu Fault Zone (TLFZ) extends in a NNE–SSW direction for more than 2000 km in Eastern China. It has been considered either as a major sinistral strike-slip fault, as a suture zone or as a normal fault. We have conducted a structural analysis of the southern segment of this fault zone (STLFZ) in the Anhui Province. The ages (Triassic to Palaeocene) of the formations affected by the faults have been re-appraised taking into account recent stratigraphical studies to better constraint the ages of the successive stages of the kinematics of the STLFZ. Subsequently, the kinematics of the faults is presented in terms of strain/stress fields by inversion of the striated fault set data. Finally, the data are discussed in the light of the results obtained by previous workers.We propose the following history of the STLFZ kinematics during the Mesozoic. At the time of collision, a  NNE orientated Tan–Lu margin probably connected two margins located north of the Dabie and Sulu collision belts. During the Middle–Late Triassic, the SCB has been obliquely subducted below the NCB along this margin which has acted as a compressional transfer zone between the Dabie and Sulu continental subduction zones. The STLFZ has been initiated during the Early Jurassic and has acted as a sinistral transform fault during the Jurassic, following which the NCB/SCB collision stopped. A  NW-trending extension related to metamorphic domes was active during the basal Early Cretaceous ( 135–130 Ma); it has been followed by a NW–SE compression and a NE–SW tension during the middle–late Early Cretaceous ( 127 to  105 Ma, possibly  95 Ma); at that time the TLFZ was a sinistral transcurrent fault within the eastern part of the Asian continent. During the Late Cretaceous–Palaeocene, the STLFZ was a normal fault zone under a WNW–ESE tension.     

Abiotic Methane Reservoirs in the Western Tianshan HP–UHP Metamorphic Belt,China

Natural gas, consisting primarily of methane(CH₄), has become a major source of clean energy in modern society in many parts of the globe. Recent experimental observations and discoveries of deep-sourced abiotic CH₄ in cold subduction zones indicate the important ability of cold subducted slabs to generate natural gas reservoirs. However, most CH₄ flux and reservoirs remain unknown and their potential is overlooked in global carbon flux estimations. Massive abiot...     

Coherent Chemical Variation Trends of the 55-25 Ma Magmatic Rocks in SE Tibet:N-S Direction Lithospheric Stretching of Eurasia during Early Stage of India-Eurasia Collision

The progressive indentation of India into Eurasia generated an E–W-trending orthogonal collision belt and a N–S-trending oblique collision belt. Compiling available data reveals that ～70% of the Cenozoic igneous rocks in eastern and southeastern Tibet are concentrated within an ENE-trending, ～550-km long and ～250-km wide magmatic zone(CMZ) that once separated the orthogonal and oblique collision belts. The Latitude 26°N Line is now its southern boundary. The onset timing of magmatism of the CMZ ...     

西拉木伦构造带克德河砂砾岩的时代及构造意义

西拉木伦构造带北部双井地区发育一套巨厚的、成熟度低的快速堆积的粗碎屑沉积建造,为同造山磨拉石沉积,前人称其为克德河砂砾岩带并将其时代分别划为中二叠世(哲斯组)、晚二叠世(林西组)。本次工作对该套地层进行了大比例尺剖面测量,对取自剖面第下、中、上(1、25、86层)三个部分的砂岩样品进行LA-ICP-MS U-Pb年代学研究,结果显示：3个样品具有相似的主要年龄区间,依次为405-485Ma、401-463Ma、363-520Ma,其峰值年龄分别为427Ma、445Ma、440Ma,锆石数量分别占总量的48％、52.5％和38.75％;其次为大于1000Ma的年龄,锆石数量分别占30.7%、22.5%、45%,且均具有1800Ma和2500Ma左右的峰值年龄,明显具有华北板块基底年龄信息;自下而上3个测年样品最年轻峰值年龄分别为312Ma、376Ma,282Ma,最年轻的锆石年龄分别为304Ma、244Ma和245Ma。在第85层杂色复成分砾岩的灰岩砾石中发现晚石炭－早二叠世阿木山组的蜓和珊瑚化石,在41及43层发现中生代孢粉化石。综合碎屑锆石测年及生物化石研究结果,克德河砂砾岩带的时代应为中三叠世。推测西拉木伦构造带经历了一个较长的演化过程,中二叠世开始华北板块和西伯利亚板块进入碰撞造山阶段, 同造山磨拉石建造(克德河砂砾岩带)标志着中亚造山带演化的终止,华北板块和西伯利亚板块的碰撞拼合造山一直延续到中三叠世才结束。     

哀牢山—红河剪切带新生代热史演化及其构造意义

笔者等通过对哀牢山—红河剪切带5件砂岩磷灰石样品裂变径迹分析,获得测试分析样品的表观年龄,对所有样品利用模拟退火法进行了热史模拟,取得其热演化史;得出哀牢山—红河剪切带在新生代发生了相似的构造演化过程,其经历了2次快速冷却剥露事件,分别发生在37～14 Ma和5. 1～0 Ma,平均冷却速率分别为3. 98℃/Ma和11. 15℃/Ma;在发生快速冷却的时间上,存在自东向西逐渐变晚的趋势,说明哀牢山—红河剪切带在新生代可能为自东向西的幕式隆升。     

鄂尔多斯盆地南部旬邑-宜君地区直罗组古层间氧化带地球化学特征及水-岩作用探讨

鄂尔多斯盆地南部旬邑-宜君地区直罗组古层间氧化带具有明显分带特征,通过对不同分带砂岩主量、微量、稀土元素及环境敏感参数特征对比研究,将旬邑-宜君地区古层间氧化带发育的水-岩作用过程划分成两个阶段：古层间氧化带形成和大规模成矿阶段、二次还原改造阶段。(1)古层间氧化带形成和大规模成矿阶段：含氧水进入目的层砂体,使砂体中Fe²⁺氧化成Fe³⁺(Fe²⁺含量最低,Fe³⁺最高);砂体中的U被氧化为U⁶⁺,形成铀酰腐殖酸盐络合物发生迁移(U、Corg、S含量最低、Th/U比值最高);长石高岭土化使Si发生流失(SiO₂含量降低);携带大量U的氧化流体运移至氧化还原过渡带(Corg、∑S含量最高、Fe²⁺含量仅低于灰绿色砂体),还原剂(有机质和黄铁矿等)将U⁶⁺还原成U⁴⁺,形成沥青铀矿;U⁴⁺与SiO₄^4-发生反应形成铀石(Th/U比...     

Determination of Early Paleozoic metamorphic event in the Longshan Complex and its geological implicationSCIEI北大核心CSCD

长期以来,陇山杂岩的归属问题一直存在争议。本文对出露于秦岭-祁连山结合部位的陇山杂岩中石榴黑云斜长片麻岩和石榴斜长角闪岩进行了详细的岩石学、P-T温压计算、独居石和榍石U-Pb年代学研究。通过详细的岩相学观察,石榴黑云斜长片麻岩的变质峰期矿物组合为石榴子石+黑云母+斜长石+石英;石榴斜长角闪岩中则识别出了以石榴子石+单斜辉石+角闪石+斜长石+石英为峰期的变质矿物组合。通过传统温压计计算,石榴黑云斜长片麻岩(样品21LS40)和石榴斜长角闪岩样品(样品21LS42-1)的峰期变质P-T条件分别为700℃、0.72GPa和710℃、0.74GPa。激光剥蚀电感耦合等离子体质谱(LA-ICP-MS) U-Pb数据表明,石榴黑云斜长片麻岩中独居石的206Pb/238U的加权平均年龄为407~435Ma。石榴斜长角闪岩中榍石的下交点年龄分别为410±7Ma、409±5Ma和426±10Ma,榍石中Zr含量温度计的计算结果分别为750℃、751℃和748℃(假定压力为0.7GPa)。本文从变质作用的角度出发,将陇山杂岩与秦岭杂岩进行温压条件和变质时代对比研究,认为陇山杂岩与东秦岭杂岩高压-超高压岩石的最后一期退变质作用和西秦岭天水地区的秦岭杂岩麻粒岩相变质作用类似,可能为北秦岭造山带的西延。     

乌干达Albert湖凹陷北部沉积特征及油气成藏模式

乌干达Albert湖凹陷是世界上最年轻的生烃凹陷,受构造和沉积控制,油气多分布于北部构造调节带。为分析Albert湖北部构造调节带内部油气成藏特征,笔者利用地震、钻井、测井和孢粉等资料,开展北部构造调节带沉积特征研究,进而分析北部构造调节带的油气成藏模式。研究表明,由于边界正断层持续活动,北部构造调节带两侧沉积特征存在差异,研究区西部发育曲流河-三角洲沉积体系;东部发育冲积扇-扇三角洲沉积体系。由于北部构造调节带西部三角洲砂体向南推进至湖盆中心,与深湖相烃源岩直接沟通,成为Albert湖盆最有利的油气汇聚区。     

基于深部地球物理信息的构造变形岩相分类研究

“构造变形岩相”填图方法的创立和应用为老矿区深部及外围的找矿工作指明了方向,在实践中取得了显著的效果,需要大力推广和深入研究。对于构造变形岩相带的深部结构认识,需要依靠地球物理信息的解译。与地球物理场性质相类似,构造变形岩相带也是一个现存的地质体;物探工作目的是要探测和揭示构造变形岩相带的埋深、轮廓、内部结构构造等特征,为确定其形成时间和演化过程提供依据。由于地质与地球物理的复杂时空关系,如果仅以新鲜岩石标本物性参数的差异作为判别标志,难以提高地球物理方法的分辨率和有效性。结合构造变形岩相进行综合解译,更能提高解释推断成果的多学科融合性。作为终极勘探目标,需要紧密结合构造控矿级序,建立构造变形岩相带的三级分类标准,提取对应的地球物理信息:一级构造变形岩相带为目标物所处的构造单元及构造应力场,及其所对应的区域地球物理场特征,如隆凹构造相间的伸展构造域;二级构造变形岩相带为目标物所处的控矿构造体系,及其所对应的矿田地球物理场特征,如岩浆核杂岩隆起-拆离构造系统;三级构造变形岩相带为目标物所在的有利成矿构造部位,及其所对应于关键剖面的地球物理特征,如侵入岩体与围岩的接触带或者含矿断裂带等。选择国际流行的典型金属矿床类型,介绍了三级构造变形岩相带的地球物理组合信息特征及其分级利用操作流程,为有效应用地球物理勘探方法开展深部找矿预测提供了范例。     

伊拉克A油田白垩系孔隙型生屑灰岩高渗透层成因及分布特征

伊拉克A油田白垩系孔隙型碳酸盐岩高渗透储层具有分布普遍、类型复杂、成因多样等特征。岩石类型主要为泥晶生屑砂屑灰岩、亮晶生屑砂屑灰岩及泥晶生屑灰岩;生物扰动加剧了碳酸盐岩储层非均质性,导致高渗透储层在全油田广泛分布。通过岩心观察、常规薄片和铸体薄片的观察和测量,孔隙度、渗透率和毛管压力的测定,综合区域地质研究成果,发现高渗层的形成受层序演化、次级相对海平面变化、沉积环境、硬底形成、生物扰动及(准)同生期暴露淋滤等复杂多因素共同控制。高渗透储层形成模式表现为Khasib组沉积时期为晚高位域期,在Kh2-1-2L段上部沉积过程中,发生首次次级相对海平面下降,形成沉积间断。沉积间断期间硬底和区域规模性的生物扰动同时发育,在Kh2-1-2L段硬底尚未被胶结的相对疏松的基质中掘穴,形成厚几十厘米、迂曲状互相贯通的生物扰动通道。沉积间断结束后,在晚期高位域层序背景下,次级相对海平面上升,松散生屑砂屑充填扰动通道。由于沉积物堆积速率较快,限制了胶结作用的发生,使扰动通道内充填物能够发育连通性好的粒间孔,而后次级相对海平面再次下降,发生(准)同生期暴露淋滤。由于扰动部位连通性好,成为溶蚀流体优势通道,导致沿扰动部位发育溶孔及扩溶缝,形成了“粒间孔+溶孔+溶缝”高渗透网络。A油田高渗透储层物性表现出发育强烈生物扰动的部位具有明显高渗特征,其孔喉较粗,排驱压力低,孔喉配位数高、连通性好。高渗层全区稳定发育,由西至东厚度逐渐增大,高渗层的分布对油田单井产量、含水上升和油田采出程度影响较大。