延庆千家店地区硅化木赋存层位及形成时代分析

北京延庆千家店土城子组中的硅化木自发现以来,得到了众多学者的关注,但关于硅化木的赋存层位和形成时代一直未有定论,目前主流观点认为硅化木广泛发育于土城子组一段和二段的下部,关于其形成时代则自侏罗纪早期至白垩纪早期的论述均有,这种争论显然不利于木化石的保护、科普和进一步深化认识。在千家店土城子组进行的考察结果展现出与前人观点不同的线索。实地考察、剖面测量和年龄测试结果显示:原位埋藏硅化木形成时代应为晚侏罗世早期,赋存层位为土城子组一段下部,而土城子组二段下部的沉积特征反应出当时水位频繁升降,水体能量剧烈变化,火山活动暂时陷入沉寂的沉积环境,较难满足形成木化石的基本要求。     

Origin of organic matter and paleoenvironment conditions of the Late Jurassic organic-rich shales from shabwah sub-basin (western Yemen): Constraints from petrology and biological markers

Late Jurassic organic-rich shales from Shabwah sub-basin of western Yemen were analysed based on a combined investigations of organic geochemistry and petrology to define the origin, type of organic matter and the paleoenvironment conditions during deposition. The organic-rich shales have high total sulphur content values in the range of 1.49–4.92 wt. %, and excellent source rock potential is expected based on the high values of TOC (>7%), high extractable organic matter content and hydrocarbon yield exceeding 7000 ppm. The high total sulphur content and its relation with high organic carbon content indicate that the Late Jurassic organic-rich shales of the Shabwah sub-basin were deposited in a marine environment under suboxic-anoxic conditions. This has been evidenced from kerogen microscopy and their biomarker distributions. The kerogen microscopy investigation indicated that the Late Jurassic organic-rich shales contain an abundant liptinitic organic matter (i.e., alginite, structureless (amorphous organic matters)). The presence of alginite with morphology similar to the lamalginite alga and amorphous organic matter in these shale samples, further suggests a marine origin. The biomarker distributions also provide evidence for a major contribution by aquatic algae and microorganisms with a minor terrigenous organic matter input. The biomarkers are characterized by unimodal distribution of n-alkanes, low acyclic isoprenoids compared to normal alkanes, relatively high tricyclic terpanes compared to tetracyclic terpanes, and high proportion of C₂₇ and C₂₉ regular steranes compared to C₂₈ regular sterane. Moreover, the suboxic to anoxic bottom water conditions as evidenced in these Late Jurassic shales is also supported based on relatively low pristane/phytane (Pr/Ph) ratios in the range of 0.80–1.14. Therefore, it is envisaged here that the high content of organic matter (TOC > 7 wt.%) in the analysed Late Jurassic shales is attributed to good organic matter (OM) preservation under suboxic to anoxic bottom water conditions during deposition.     

柴达木盆地北缘侏罗系页岩气地质条件

侏罗系泥页岩是柴达木盆地的主力烃源岩之一,具备形成页岩油气的地质条件。对采自柴北缘鱼卡、大煤沟、小煤沟、开源、绿草沟、大头羊等煤矿附近地表露头的11块中侏罗统泥页岩样品进行单样品多参数实验分析,探讨了陆相页岩有机地化、储层物性、含气量等参数之间的关系,建立了页岩气资源评价参数体系。结果表明,柴达木盆地北缘中侏罗世处于浅湖-半深湖湖相沉积,断裂较发育,泥页岩富含有机质,具有低孔、低渗、低熟、较高含气量等特点,具备形成页岩油气的地质条件,进一步的勘查开发需优选地层压力系数高、保存条件较好、脆性矿物含量高的页岩气甜点区。     

西藏改则县多不扎地区上侏罗统对望山组的建立及意义

对望山组是发育在羌南板块南缘的一套岩石组合,以安山岩、流纹岩、玄武质凝灰岩为主,有少量的玄武安山岩夹层,具有明显的岩浆喷出相和沉积相韵律分布的特点。利用LA-ICP-MS同位素定年技术对对望山组安山岩中的锆石进行了U-Pb同位素测年,获得锆石的~(206)Pb/~(238)U年龄加权平均值为150.5±0.6Ma,表明对望山组的形成时代为晚侏罗世中晚期,在详细剖面测制和区域对比的基础上建立了对望山组。对望山组的建立对完善班公湖-怒江缝合带的地层系统、探讨班公湖-怒江洋的晚侏罗世构造演化具有重要的地质意义。     

西藏谢通门地区中侏罗世花岗岩的地球化学特征及时代依据

西藏谢通门县一带区域上属于冈底斯花岗岩带南亚带,侵入岩极其发育,目前填绘有白垩纪、古近纪和新近纪岩体。通过同位素年代学研究,获得12个锆石的U-Pb同位素年龄数据,在原划归白垩纪、古近纪和新近纪岩体中解体出侏罗纪侵入体,按其岩石类型特征,归并为早侏罗世东热村序列和中侏罗世东嘎乡序列。其中,在约拉嘎莫岩体中获得锆石U-Pb同位素年龄166.9±2.8Ma,时代为中侏罗世巴柔期。     

Morphological and Phylogenetic Study Based on New Materials of Anchiornis huxleyi (Dinosauria,Theropoda) from Jianchang,Western Liaoning,China

Anchiornis huxleyi, which is a member of the Middle–Late Jurassic Yanliao Biota, is the smallest feathered dinosaur ever known. It has been described as a critical link between feathered dinosaurs and birds. Recent studies, including those of Anchiornis, Xiaotingia, Eosinopteryx and Aurornis, challenged Archaeopteryx as the most basal bird. The new Anchiornis huxleyi specimens that are described in this paper show some minor different characters compared to previously reported Anchiornis specimens, which has revised the character list of Anchiornis and indicates a different phylogenetic point from former opinions.     

南海北部潮汕坳陷侏罗系沉积特征及对储层的控制作用研究

南海北部潮汕坳陷侏罗系具有很大的油气勘探潜力,沉积特征对其储层的发育具有明显的控制作用。通过对研究区最新地震资料精细解释,可以划分出4个典型地震反射界面和3个地震反射层,根据层序界面圈出侏罗系分布特征和残留厚度;通过地震相-沉积相转换对比分析研究,识别出侏罗纪地层不同时期的沉积相类型及其分布特征,重塑了潮汕坳陷侏罗系沉积演化史。该区主要发育5类沉积相、8种沉积亚相,其中滨岸三角洲前缘亚相和深水扇中亚相分别控制了碎屑流砂岩优质储层的发育;此外,浊流砂岩储层主要受控于物源供给的影响,距离三角洲砂体朵叶越近,滑塌浊积体数量越多,面积也越大。总体上,滨岸三角洲前缘亚相、深水扇中亚相和滑塌浊积体是研究区良好的储集相带,该类储集体由于埋藏较深加之被泥岩覆盖,对油气聚集较为有利。     

嫩江科洛地区晚侏罗世深熔花岗岩对嫩江-黑河构造带的响应

通过对嫩江-黑河构造带内的岩石建造研究,在嫩江科洛地区识别出一套深熔花岗岩体,岩石宏观上为一套具非典型花岗岩结构的深熔型侵入岩,具交代结构、斑杂状构造和眼球状构造。对深熔花岗岩进行了锆石LA-ICP-MS U-Pb年龄测试,获得了3组不谐和的U-Pb年龄: 390 Ma、157~163 Ma和113 Ma。其中,113 Ma年龄代表了岩石遭受后期变质热事件年龄; 157~163 Ma的年龄代表了原岩结晶年龄。综合分析深熔花岗岩成因,认为其主要与嫩江-黑河断裂深部韧性剪切热效应作用下发生的深熔有关,深熔花岗岩的划分和厘定为深入研究嫩江-黑河断裂带在中生代的活动提供了新的素材。     

羌塘盆地晚侏罗世夏里组磁学参数指示的沉积环境及其成盐意义

羌塘盆地位于青藏高原中部,是一个具有沉积钠盐、钾盐远景的蒸发岩盆地。最近在羌塘盆地上侏罗统夏里组中发现多处具有钾、钠异常的盐泉这一重要的找钾盐线索,然而目前对上侏罗统夏里组的古环境演变仍然不甚了解,限制了对晚侏罗世羌塘盆地的成盐(成钾)条件和可能的层位等重大科学问题的理解。因此本文以热磁分析为主,对羌塘盆地雁石坪地区上侏罗统夏里组沉积物进行高分辨率岩石磁学研究,并讨论其古环境意义。最后,根据成盐(成钾)理论,综合分析羌塘盆地上侏罗统夏里组成盐(成钾)的构造、气候和物源条件。κ-T曲线、磁滞回线和热退磁结果共同表明磁铁矿和赤铁矿是夏里组的主要载磁矿物;磁学参数分析表明夏里组上段赤铁矿含量相对增加,揭示夏里组上段形成于干旱气候环境;综合分析构造、气候和物源条件表明,羌塘盆地上侏罗统夏里组上段最为具备良好的成盐(成钾)条件。     

Middle Jurassic–Early Cretaceous tectonic evolution of the Bayanhushuo area,southern Great Xing’an Range,NE China: constraints from zircon U–Pb geochronological and geochemical data of volcanic and subvolcanic rocks

This study presents new zircon U–Pb geochronology, geochemistry, and zircon Hf isotopic data of volcanic and subvolcanic rocks that crop out in the Bayanhushuo area of the southern Great Xing’an Range (GXR) of NE China. These data provide insights into the tectonic evolution of this area during the late Mesozoic and constrain the evolution of the Mongol–Okhotsk Ocean. Combining these new ages with previously published data suggests that the late Mesozoic volcanism occurred in two distinct episodes: Early–Middle Jurassic (176–173 Ma) and Late Jurassic–Early Cretaceous (151–138 Ma). The Early–Middle Jurassic dacite porphyry belongs to high-K calc-alkaline series, showing the features of I-type igneous rock. This unit has zircon ε_Hf(t) values from +4.06 to +11.62 that yield two-stage model ages (T_DM2) from 959 to 481 Ma. The geochemistry of the dacite porphyry is indicative of formation in a volcanic arc tectonic setting, and it is derived from a primary magma generated by the partial melting of juvenile mafic crustal material. The Late Jurassic–Early Cretaceous volcanic rocks belong to high-K calc-alkaline or shoshonite series and have A₂-type affinities. These volcanics have ε_Hf(t) and T_DM2 values from +5.00 to +8.93 and from 879 to 627 Ma, respectively. The geochemistry of these Late Jurassic–Early Cretaceous volcanic rocks is indicative of formation in a post-collisional extensional environment, and they formed from primary magmas generated by the partial melting of juvenile mafic lower crust. The discovery of late Mesozoic volcanic and subvolcanic rocks within the southern GXR indicates that this region was in volcanic arc and extensional tectonic settings during the Early–Middle Jurassic and the Late Jurassic–Early Cretaceous, respectively. This indicates that the Mongol–Okhotsk oceanic plate was undergoing subduction during the Early–Middle Jurassic, and this ocean adjacent to the GXR may have closed by the Late Middle Jurassic–Early Late Jurassic.