Climate change and local adaptation strategies in the middle Inner Mongolia,northern China

According to records of 17 meteorological stations distributed in the study area, climate change of the middle Inner Mongolia in northern China was analyzed in this paper. Based on SPOT VGT data, combined with field investigation, local vegetation change was detected in the last 10 years. The results show that annual mean air temperature obviously rose, while precipitation slightly decreased in fluctuation in the study area during the last 50 years. Air temperature increasing rates are +0.318°C 10 year⁻¹ during 1960-2009 and +0.423°C 10 year⁻¹ during 1980–2009, while precipitation decreasing rates are −2.91 mm 10 year⁻¹ during 1960–2009. There were five different dry or wet periods from the 1960s to the 2000s in order, and the wetter 1990s and the drier 2000s changed dramatically in the study area. Local climate totally tend to warm–dry conditions during the last 50 years. According to coefficient of variation (Cv) of yearly growing-season cumulative NDVI value and yearly NDVI maximum in pixel scale, vegetation had experienced huge temporal and spatial variation during the last 10 years. Recently, frequent droughts and dust storms seriously affected local agriculture and grazing activities, and resulted in heavy economic loss, especially over the drought period of 1999–2001. Faced with those drought disasters accompanied with strong dust storms, the local authorities proposed the enclosing-transferring strategy and made great efforts to adapt overt climate change and improve environment, including making selective emigration, decreasing livestock numbers, fencing grasslands and building forage production bases with irrigation instruments and actively adjusting industry structure. However, some effects and potential problems of this adaptation strategy still need to be comprehensively assessed further in longer time scales and aimed at different sub-regions.     

冀北金台子盆地早白垩世酸性火山岩地球化学、锆石年代学及其地质意义

华北克拉通在中生代以来遭受了显著破坏。前人的研究对克拉通破坏的机制和峰期取得了较大共识, 但是关于克拉通破坏的启动时间一直存在争议。本文通过对冀北金台子中生代盆地构造特征及其填充的火山岩地球化学和年代学进行分析, 为华北克拉通破坏启动时间提供新的约束。研究表明, 金台子盆地为一伸展断陷盆地。盆地呈北东-南西向展布, 东侧被正断层控制, 西侧为地层超覆边界。盆地内自下而上发育后城组、白旗组、啕北营组、九佛堂组火山-沉积组合。后城组是一套稳定的河流相红色砂砾岩沉积地层;白旗组和啕北营组主体为巨厚层流纹岩、流纹质凝灰熔岩, 局部夹安山岩和火山碎屑岩;九佛堂组是一套以砾岩、砂砾岩等为主体的碎屑岩。地球化学分析表明金台子盆地中发育的酸性火山岩源于地壳重熔。锆石U-Pb年代学研究显示, 金台子盆地内流纹岩自约145 Ma开始广泛喷发并形成巨厚层的酸性火山岩地层, 表明此时在华北北缘地区的岩石圈减薄和破坏可能就已非常剧烈, 据此华北克拉通在其北缘的破坏至少应早于145 Ma。     

GRAPES全球四维变分同化系统极小化算法预调节

在进行多次外循环更新的增量分析框架下,前一次极小化迭代过程中产生的信息可提供给下一次极小化做预调节。该文在GRAPES全球四维变分同化系统中对极小化算法——L-BFGS算法实施了这种预调节,通过全观测的个例试验和批量试验进行评估,发现进行预调节后L-BFGS算法的收敛效率得到明显提高,而且在1个月的循环试验中表现十分稳定。该工作可以帮助GRAPES全球四维变分同化系统有效减少极小化的迭代次数,有利于满足业务化运行的时效要求。另外,间隔6 h和间隔24 h的两次4DVar分析对应的海森矩阵变化不大,因此,前一时刻极小化过程产生的信息提供给后一时刻的极小化进行预调节也有一定效果。     

关于梅雨研究的回顾与展望

从梅雨的划分、梅雨的降水分型、梅雨与季风的关系及梅雨的影响因子几个方面,对前人的研究成果进行了回顾和讨论。最后,提出梅雨研究仍需解决的问题：（1）江淮流域梅雨季节的开始至今仍没有一个客观统一划定标准;（2）南海季风、印度季风等季风子系统对梅雨的影响大小及其机制尚需进一步研究讨论;（3）应针对梅雨季节内江淮流域不同的降水分布型,寻找其前期预兆信号进行深入研究;（4）应特别注意特定海温分布型对梅雨的影响,并从中找出影响梅雨的关键区域和影响的关键时段;（5）积冰和雪盖与梅雨异常的关系仍需进一步求证,影响机制还需进一步探索。     

热液体系氩同位素示踪研究

 采用分阶段加热爆裂法测定了不同成因热液矿床脉石英流体包裹体的氩同位素,计算出各温度段内大气氩的相对含量,从而,总结出大气降水热液矿床、再平衡岩浆水热液矿床等成矿流体的氩同位素组成特征及其演化规律。典型的大气降水热液矿床,其成矿流体以具有高大气Ar组分(约95%-100%)为特征;再平衡岩浆水热液矿床成矿流体的Ar同位素组成特征取决于与其有成因关系的初始岩浆水的Ar同位素组成及矿源层和围岩的性质,产于古老变质岩中的,一般以具有低大气Ar组分(约6%-20%)为特征,其它的再平衡岩浆水热液矿床在主成矿温度范围内一般为50%-60%左右。     

Identifying gravity anomalies caused by granitic intrusions in Nanling mineral district,China: a multifractal perspective

Several power‐law relationships of geophysical potential fields have been discussed recently with renewed interests, including field value–distance () and power spectrum–wavenumber () models. The singularity mapping technique based on the density/concentration–area (C–A) power‐law model is applied to act as a high‐pass filter for extracting gravity and magnetic anomalies regardless of the background value and to detect the edges of gravity or magnetic sources with the advantage of scale invariance. This is demonstrated on a synthetic example and a case study from the Nanling mineral district, Southern China. Compared with the analytic signal amplitude and total horizontal gradient methods, the singularity mapping technique provides more distinct and less noisy boundaries of granites than traditional methods. Additionally, it is efficient for enhancing and outlining weak anomalies caused by concealed granitic intrusions, indicating that the singularity method based on multifractal analysis is a potential tool to process gravity and magnetic data.     

Reviews on Potash Deposit Metallogenic Conditions

Potash salt is one of key scarce strategic resources. Searching for large scale of potash salt deposit is one big problerm which Chinese academic community faces. Many new discoveries of world potash deposit have been made in recent ten years, which provide abundant practical information and complement the potash metallogenic theory. Through the summary of the potash forming characteristics at home and abroad, the paper studies the potash forming time, tectonic condition, paleogeographic condition, paleoclimate, basin location and salt source. Potash is mainly formed in Permian, Cretaceous, late Jurassic, Cambrian and Devonian. The combination of structure and environment helps to form large scale of evaporation. The climate cycle is related with crust activity. As the other ore deposit, the formation of potash ore also needs dry climate. Potash is the product of final stage in brine evolution, and therefore, it needs persistent drought climate. However, the climate condition is very complicated. Drought climate belt also occurs in humid climate stage, which is controlled by geomorphology. Potash ore can also form in local drought condition. Generally, potash forms in rock salt basin. However, the actual situation is very complicated. Some potash basin is coincided with rock salt basin, some is on one side of rock salt basin; and some are even in the outside of rock salt basin. Salt materials can be from three sources: marine source, terrigenous source and deep source.The paper gives an overview of the research status about the potash deposit forming conditions, which has great guiding significance for searching potash deposit in China. The paper also summarizes the three types of metallogenic models for potash deposit, including epicontinental metallogenic model, abnormal marine evaporation model and rift valley model. The three models are mainly different in material sources, in which the potash in epicontinental metallogenic model is from seawater; the potash in abnormal evaporation model is from nonmarine brine and the potash in rift valley model is mainly from deep material of volcanic activity.     

Impact of impoundment on groundwater seepage in the Three Gorges Dam in China based on CFCs and stable isotopes

It is a common concern that the groundwater flow field caused by the Three Gorges Dam changes the regional seismic activity and environment. The changes in the seepage region could be effectively reflected through the analysis of the groundwater age using chlorofluorocarbons (CFC)-based techniques. In this study, the influences of the reservoir water on groundwater and the seepage region boundary of the reservoir were investigated using CFCs, stable isotopes, and water level in groundwater, reservoir water, and spring water during the water storage process of the Three Gorges Reservoir. The results show that the water supplied by the groundwater is older, whereas the water supplied by the reservoir and the springs is younger. With an increase in the water level of the reservoir, the water in well W3, which is located at the vice dam of the head region, becomes older due to the reservoir loading effect, whereas the water in well W4 become younger due to the lateral seepage of reservoir water. This finding indicates that the groundwater seepage regions in wells W3 and W4, which are located at upstream of the reservoir, are all influenced by the Three Gorges Reservoir. In contrast, the sampling points in the northern section of the Xiannvshan fault zone, which is farther from the dam, did not exhibit any direct hydraulic connection between the groundwater and the reservoir water; thus, the reservoir seepage effects may not affect the northern part of the Xiannvshan fault zone. These research results provide important reference data that can be used to analyze the effects of the Three Gorges reservoir storage on the regional environment.     

Time scale of an early to mid-Paleozoic orogenic cycle of the long-lived Central Asian Orogenic Belt, Inner Mongolia of China: Implications for continental growth

We present a detailed, new time scale for an orogenic cycle (oceanic accretion–subduction–collision) that provides significant insights into Paleozoic continental growth processes in the southeastern segment of the long-lived Central Asian Orogenic Belt (CAOB). The most prominent tectonic feature in Inner Mongolia is the association of paired orogens. A southern orogen forms a typical arc-trench complex, in which a supra-subduction zone ophiolite records successive phases during its life cycle: birth (ca. 497–477 Ma), when the ocean floor of the ophiolite was formed; (2) youth (ca. 473–470 Ma), characterized by mantle wedge magmatism; (3) shortly after maturity (ca. 461–450 Ma), high-Mg adakite and adakite were produced by slab melting and subsequent interaction of the melt with the mantle wedge; (4) death, caused by subduction of a ridge crest (ca. 451–434 Ma) and by ridge collision with the ophiolite (ca. 428–423 Ma). The evolution of the magmatic arc exhibits three major coherent phases: arc volcanism (ca. 488–444 Ma); adakite plutonism (ca. 448–438 Ma) and collision (ca. 419–415 Ma) of the arc with a passive continental margin. The northern orogen, a product of ridge-trench interaction, evolved progressively from coeval generation of near-trench plutons (ca. 498–461 Ma) and juvenile arc crust (ca. 484–469 Ma), to ridge subduction (ca. 440–434 Ma), microcontinent accretion (ca. 430–420 Ma), and finally to forearc formation. The paired orogens followed a consistent progression from ocean floor subduction/arc formation (ca. 500–438 Ma), ridge subduction (ca. 451–434 Ma) to microcontinent accretion/collision (ca. 430–415 Ma); ridge subduction records the turning point that transformed oceanic lithosphere into continental crust. The recognition of this orogenic cycle followed by Permian–early Triassic terminal collision of the CAOB provides compelling evidence for episodic continental growth.