赣杭构造带中段岩石圈电性结构研究

赣杭构造带（简称赣杭带）位于扬子板块和华夏板块的结合部,是中国重要的铀多金属矿成矿带,发育一系列中酸性火山—侵入杂岩;前人对岩浆喷发和侵入的地球动力学背景仍然存在诸多争议。文章对赣杭带中段（盛源盆地）及邻区收集的大地电磁测深（MT）数据,利用MT相位张量分解技术、二维非线性共轭梯度法（NLCG）等技术手段进行处理和反演获得到了研究区可靠的岩石圈电性结构。结合已有资料分析表明：赣杭带中段浅部火山—侵入杂岩带存在东南方向下倾的高导带和深部软流圈高导区且相连,揭示了该地区中酸性岩浆活动受区域江绍深断裂控制,在晚中生代岩石圈伸展作用下沿着区域深断裂上升侵入和喷发形成火山—侵入杂岩;该岩浆活动处在伸展构造环境与同期Izanagi板块俯冲后撤有关。     

青藏高原壳幔结构构造的基本特征

青藏高原是新生代以来由于印度板块与欧亚板块碰撞而迅速隆起,平均海拔超过4000 m的高原,是研究碰撞过程和形成演化的理想窗口。有关青藏高原的碰撞过程及印度板块岩石圈北缘界线,至今仍然存在较大争议,这可能主要是由于不同研究方法获得认识的差异性和局限性所导致。基于此,本文利用前人深部结构资料,讨论了高原岩石圈的壳幔构造及物质组成等,并从新的地质视角讨论了班怒带的大地构造属性。通过梳理前人的深部结构资料,认为青藏高原的壳幔岩石圈结构较为复杂,如高原内部岩石圈厚度显著大于周缘地区,中下地壳及上地幔广泛分布着低速高导层,这些特殊的地质地球物理结构是印亚板块碰撞的结果。此外,本文进一步对比分析了班怒带的地质与地球物理结构,揭示该构造带两侧存在显著的差异,认为其是印度岩石圈的北缘,这对于认识青藏高原的形成演化具有重要的意义。     

基于宽频大地电磁法的页岩气探测实践——以川西南沐川地区须家河组为例

四川盆地上三叠统须家河组陆相富有机质页岩较为发育,页岩连续厚度较大,含气性好,有望开辟四川盆地页岩气新区新层系。然而,复杂的人文干扰（城镇密集、人口众多）和较大的埋藏深度（2000~3000m）挑战了页岩气地球物理勘探的精度,这在很大程度上制约了川西南沐川地区三叠系须家河组页岩气的进一步勘探。本文在分析前人研究资料基础上,优选了川西南沐川地区须家河组作为新区新层系的探测目标,根据研究区地质情况,构建理论电性模型,通过正演模拟和“已知”钻孔标定方法试验,确定了宽频大地电磁法的适用性和有效性。进而在重点页岩气远景区部署一条宽频大地电磁剖面,通过数据处理分析,结合地质资料获得了研究区深部电性结构,认为研究区一带地层连续、完整,断裂不发育,具有稳定的地质结构,其中上三叠统须家河组发育较大厚度的富有机质页岩,可作为本区页岩气勘探的新区新层系,具有良好的页岩气、致密气资源前景。同时,证实了在3000m以浅页岩气探测方法中,宽频大地电磁法（BMT）可以有效地识别富有机质页岩规模和空间展布特征,是一种快速、经济、无损有效的页岩气探测方法,可以为页岩气勘探提供先导依据,同时也为同类地质情况页岩气探测提供应用示范。     

Process and Mechanisms of Deep Fluid Effects on Hydrocarbon Generation and Pore Space in Shale: A Case Study from the Mesoproterozoic Xiamaling Formation in the Zhaojiashan Section

Heat carried by deep fluid might greatly affect hydrocarbon generation and pore space in shale. Dyke intrusion carrying high levels of heat may be a means by which to explore the influence of deep fluid on shale reservoirs. This study evaluates hydrocarbon generation and analyzed the evolution of shale storage space in the third member of the Xiamaling Formation in the Zhaojiashan section, Hebei Province, based on experimental data such as TOC, SEM, VRo, low-temperature N2 adsorption and high-pressure mercury injection. The results show that the dyke intrusion reduced the shale TOC content drastically―by up to 77%―and also induced instantaneous hydrocarbon generation over a range about 1.4 times the thickness of the intrusion. Furthermore, the dyke intrusion might transform organic pores in surrounding shales into inorganic pores. There were two shale porosity peaks: one appeared when VRo = 2.0%, caused by the increase of organic pores as thermal maturity increased, the other occurred when the VRo value was between 3% and 4%, caused by the increase of inorganic mineral pores. It can be concluded that dyke intrusion can be an effective tool with which to study how deep fluid affects instantaneous hydrocarbon generation and pore space in shale.     

Petrogenesis and Tectonic Implications of A-type Granites in Zhaheba in the East Junggar Region of Xinjiang, China: Evidence from Geochronology, Geochemistry and Sr-Nd Isotopic Compositions

The magma source, petrogenesis, tectonic setting and geochronology of the late Paleozoic A-type granites widely exposed in the Zhaheba area, East Junggar, have thus far not been well-constrained. A better understanding of these issues will help to reveal the magmatic processes and continental growth of Central Asia. The A-type granites in Zhaheba include the Ashutasi alkaline granites and the Yuyitasi syenogranites, which were emplaced at 321.5 ± 4.8 Ma and 321.7 ± 0.6 Ma, respectively. The major rock-forming minerals are orthoclase, perthite, arfvedsonite and quartz, which exhibit the following principal geochemical characteristics of A2-type granites. (1) Their REE distribution curves each exhibit a ‘V’-shaped pattern and a marked depletion in Eu. They are rich in large-ion lithophile elements Rb, Th and U as well as high-field-strength elements Nb, Ta, Zr and Hf, but significantly depleted in Ba, Sr, P and Ti. (2) Their (87Sr/86Sr)i values (0.7021–0.7041), εNd(t) values (4.57–5.16) and REE distribution patterns are in basic agreement with those of the Kalamaili A-type granite belt in East Junggar. The TDM2 values of the alkaline granites and syenogranites range from 661 to 709 Ma. The A-type granites may be the products of upwelling asthenosphere-triggered partial melting of immature lower crust. The alkaline granites were late-stage products of crystallization and differentiation. Compared to the syenogranites, the alkaline granites are significantly lower in K2O, Na2O, Al2O3, FeO, MgO and CaO, but significantly higher in incompatible elements (e.g., SiO2, Rb, and Sr). The magmatic crystallization temperatures of the syenogranites and alkaline granites are 874°C and 819°C, respectively. As their age gradually decreases (peak ages: 322 Ma and 307 Ma, respectively), there is a gradual decrease in the TDM2 of the A-type granites and a gradual increase in the εNd(t) value from the Ulungur belt to the Kalamaili belt in East Junggar. The study of A-type granites is therefore one of the keys to understanding the laws and mechanisms of crustal accretion during the Phanerozoic period, as well as also being of great significance for understanding the Paleozoic accretion.     

中国干旱-半干旱区表土bGDGTs与气候环境因子数据再分析

文章通过收集中国北方干旱-半干旱区域已发表的bGDGTs数据,重新计算了不同地区表土bGDGTs各组分与温度及pH等环境因子之间的相关关系。主要获得以下认识：1)不同于干旱区,半干旱区bGDGTs的异构体指标与土壤pH表现为强相关,在4个异构体指标(IBT、 CBT′、 IR′_IIa、 IR′_IIIa)中CBT′、 IR′_IIIa计算的pH结果精度较高;2)半干旱区f（5 me）与pH表现为强相关（-0.847）,指示了基于5-甲基bGDGTs的指标同样具有重建半干旱区pH的潜力。但是目前缺乏CBT′_5ME-pH之间的转换函数;3)全球温度校正方程计算得出的温度误差普遍大于中国区域校正方程（中国北方、青藏高原等区域）获取的温度误差。通过整合数据重新计算发现4个区域温度校正方程(MBT′_5ME、 Tmr、 MAATsr、 Index 1)计算的温度结果具有较小的误差,且在半干旱区重建的温度结果更为精确;另外MAATsr、 Index 1的区域温度校正方程也适用于干旱区的温度重建,...