Meso‐Cenozoic Tectonothermal History of Permian Strata,Southwestern Weibei Uplift: Insights from Thermochronology and Geothermometry

This study provides an integrated interpretation for the Mesozoic-Cenozoic tectonothermal evolutionary history of the Permian strata in the Qishan area of the southwestern Weibei Uplift, Ordos Basin. Apatite fission-track and apatite/zircon(U-Th)/He thermochronometry, bitumen reflectance, thermal conductivity of rocks, paleotemperature recovery, and basin modeling were used to restore the Meso-Cenozoic tectonothermal history of the Permian Strata. The Triassic AFT data have a pooled age of ～180±7 Ma with one age peak and P(χ2)=86%. The average value of corrected apatite(U-Th)/He age of two Permian sandstones is ～168±4 Ma and a zircon(U-Th)/He age from the Cambrian strata is ～231±14 Ma. Bitumen reflectance and maximum paleotemperature of two Ordovician mudstones are 1.81%, 1.57% and ～210°C, ～196°C respectively. After undergoing a rapid subsidence and increasing temperature in Triassic influenced by intrusive rocks in some areas, the Permian strata experienced four cooling-uplift stages after the time when the maximum paleotemperature reached in late Jurassic:(1) A cooling stage(～163 Ma to ～140 Ma) with temperatures ranging from ～132°C to ～53°C and a cooling rate of ～3°C/Ma, an erosion thickness of ～1900 m and an uplift rate of ～82 m/Ma;(2) A cooling stage(～140 Ma to ～52 Ma) with temperatures ranging from ～53°C to ～47°C and a cooling rate less than ～0.1°C/Ma, an erosion thickness of ～300 m and an uplift rate of ～3 m/Ma;(3)(～52 Ma to ～8 Ma) with ～47°C to ～43°C and ～0.1°C/Ma, an erosion thickness of ～500 m and an uplift rate of ～11 m/Ma;(3)(～8 Ma to present) with ～43°C to ～20°C and ～3°C/Ma, an erosion thickness of ～650 m and an uplift rate of ～81 m/Ma. The tectonothermal evolutionary history of the Qishan area in Triassic was influenced by the interaction of the Qinling Orogeny and the Weibei Uplift, and the south Qishan area had the earliest uplift-cooling time compared to other parts within the Weibei Uplift. The early Eocene at ～52 Ma and the late Miocene at ～8 Ma, as two significant turning points after which both the rate of uplift and the rate of temperature changed rapidly, were two key time for the uplift-cooling history of the Permian strata in the Qishan area of the southwestern Weibei Uplift, Ordos Basin.     

水泥土挡墙压顶梁对基坑变形影响研究

在分析水泥土挡墙变形机理基础上,对压顶梁的作用进行了研究,并深入探讨了压顶梁的有效利用范围和优化措施。工程实例表明,合适的压顶梁是控制挡墙变形的一种有效措施。     

西湖凹陷杭州斜坡构造差异及其对成藏的影响

杭州斜坡是西湖凹陷油气勘探的新区,构造特征的研究是开展石油地质条件研究的基础.通过对杭州斜坡的结构、主控断裂的演化及其对油气运移控制作用的分析,探讨了斜坡结构差异及其对油气成藏的影响.研究结果表明:杭州斜坡分为北段、中段和南段三个部分,中段断层走向为北北东向,单个断层的延伸长度小但数量多,存在倾向东和倾向西的顺向断层和...     

陕西金矿床类型及其找矿方向

通过对陕西金矿资源的分析、总结，将陕西金矿成因类型划分为7类14亚类；与金矿有关的成矿系列划分为3个矿床成矿系列组合，7个成矿系列类型，10个成矿系列和4个亚系列；金矿床空间分布严格受隐伏基底和出露基底，隐伏岩体、重磁吻合构造，构造和成矿时代的控制；与金成矿有关的Ⅲ级成矿区(带)有4条，有关的Ⅳ级成矿区(带)有10条，有关的Ⅴ级主要金成矿区(带)有16条；提出了金矿新的找矿方向，为今后本区金矿地质找矿的新突破提供信息。     

强震作用下冰水域桥墩动力响应研究分析

地震作用下冰水域桥墩受到动水压力与动冰荷载的的双重影响。基于Morison动水理论和Croteau动冰力模型,提出一种适用于冰水域桥墩动力时程反应分析的简便计算模型,通过振动台试验验证了其有效性,并分析了海冰质量和水深对冰海域桥墩动力响应的影响。结果表明,强震作用下有冰时墩底最大曲率比无冰时最大增加8.93倍,桥墩被自由冰包围时,墩底截面出现最大曲率时对应的海冰质量随着水深的增加而变大;随着冰质量的持续增大,墩身最大位移易超越极限位移,造成桥梁垮塌,在桥梁设计中应重点考虑。     

重庆市主体功能区识别的主导因素与空间稳定性约束机理

主体功能区规划已上升为国家制度和战略,对中国长期空间发展格局优化与再组织将发挥积极的引导和约束作用。从地域性角度出发,探寻主体功能区发生性(形成与演化)和反馈性(识别与规划)时空机理与规律是地理学具有时代意义的重要科学问题。以重庆市为例,通过国土空间开发条件综合评价,识别了主体功能区划分的适宜性空间格局。基于对西南山区发展约束条件的基本认识,提出了地域主体功能空间分异的主导性约束假设,设定地形和区位为原生性主导因素,验证了其与区划指标系统的定量关联性,以此为基础解析了主导因素约束机理并提出了地域主体功能区的空间稳定性机制。研究发现:①开发与保护适宜性识别结果的格局指向清晰。城市化适宜的区域主要集中于都市区和部分周边区县,区域副中心(万州和黔江)适宜性也相对较高。生态保护适宜的区域集中于渝东北秦巴山区及部分三峡库区区县,同时包括渝东南武陵山区所在区县。②地形和区位因子在本区域对主体功能区的识别与形成具有主导约束作用。回归分析显示,主体功能区划指标与地形因子相关性水平达到显著的超过70%,区位因子超过40%;两者综合后与区划标志变量(A、B指数)的相线性相关拟合度R2均超过0.8;地理探测器发现,地形和区位因子对区划指标的约束性分别有9个和7个达到0.05显著性水平,对A、B指数的解释度分别约为70%和60%,两者叠加后,约束水平全部达到显著,对A、B指数的解释度在90%左右。③空间稳定性机制表现为两个方面,其一是基于主导因素约束的稳定性传递机制,称为客观稳定性;其二是基于指标体系的局域相对性和算法的内部抵消机制,称为主观稳定性。两种机制的协同性验证了区划技术系统的地域适应性和科学性。     

Replacing fishmeal with soybean meal affects survival,antioxidant capacity,intestinal microbiota,and mRNA expression of TOR and S6K1 in Macrobrachium rosenbergii

Using alternative plant-derived dietary protein to replace fishmeal, combined with practical evaluation indexes, is a recent focus for aquaculture practices. An 8-week feeding experiment with giant freshwater prawn Macrobrachium rosenbergii post-larvae was conducted to determine the effects of replacing fishmeal(FM) with soybean meal in the feed, in terms of growth performance, antioxidant capacity, intestinal microbiota, and m RNA expression of target of rapamycin(TOR) and ribosomal protein S6 ...     

Regional Equity and Influencing Factor of Social Assistance in China

Social assistance is the last safety net in the social security system and plays a vital role in poverty alleviation in countries around the world. Promoting the equal financial assistance is meaningful to achieve equalization of social assistance. Based on the provincial panel data from 2002 to 2017, this paper analyzes the dynamic characteristics and main influencing factors of the equity of social assistance in China, using the Theil index and geographically weighted regression(GWR) model. Th...     

贝类净化技术研究现状与展望

随着养殖水域环境问题日益凸显,贝类食品安全问题越来越受到重视,贝类在进入流通环节前进行净化将成为不可缺少的处理环节。本文从贝类净化工艺类型、净化用水处理技术,以及贝类净化对风味的影响等方面对当前国内外研究进展进行了总结梳理,并提出下一步贝类净化应重点解决的问题,为深入开展贝类净化相关研究提供参考。     

Cenozoic Crustally-derived Carbonate-rich Magmatic Rocks in West Junggar,North Xinjiang,Western China: Geochronology,Geochemistry and Tectonic Implications

The carbonate-rich magmatic rocks of West Junggar are distributed in the Baijiantan and Darbut ophiolitic mélanges in the forms of extrusive rocks overlying the mélanges and dykes, either along the margins of the mélange or cross-cutting components of mélanges. Chilled margin and flow structures are present. A SHRIMP zircon U-Pb age of 39.7 ± 1.3 Ma indicates that these carbonate-rich rocks in West Junggar were formed during the Eocene. They have low concentrations in REEs, Th, U, Nb, Ta and are characterized by extremely low εN d(t), high(87 Sr/86 Sr)i ratios, relatively high δ18 OV-SMOW values and high δ13 CV-PDB values, which is similar with most sedimentary carbonates. Furthermore, no contemporaneous mantle-derived silicate rocks have yet been found in West Junggar. The carbonate-rich rocks in West Junggar are thus distinct from mantle-derived carbonatites and are interpreted to result from melting of the Carboniferous sedimentary carbonates at crustal levels, these rocks therefore being referred to as 'crustal carbonatites'. The Eocene crustal carbonatites in West Junggar and other Cenozoic magmatic rocks in North Xinjiang are generally situated along regional strike-slip faults or fault intersections. Therefore, we propose that the reactivation of the Darbut and Baijiantan crustal-scale strike-slip fault zones(ophiolitic mélanges), due to the far-field effects of the Indian-Eurasian collision, enables decompression melting of the underlying continental lithospheric mantle. These resulting melts ascended to the lower crust through the strike-slip faults, causing partial melting of the Carboniferous carbonaceous sediments. The crustal carbonatites in West Junggar provide a new piece of evidence for Cenozoic magmatism in North Xinjiang and are also significant for the investigation of tectono-magmatic relations in North Xinjiang and the Central Asian Orogenic Belt.