从岩石到土壤再到水系沉积物：风化过程的岩性地球化学基因

不活动元素的稳定性使得风化岩石、土壤和水系沉积物等风化产物能够保留新鲜母岩的元素特征,它们之间的含量变化趋势有可能从母岩传递到其风化产物中,这类似于生物学中基因遗传。仿照生物学中基因的特性提出了地球化学基因的概念及其构建方法,为了比较地球化学基因的相似程度进而提出基因相似度的概念及其计算方法。以风化过程中11种不活动元素为例,基于中国酸性岩、中性岩、基性岩的元素丰度数据构建了表征岩石及其风化产物地球化学特性的岩性地球化学基因,其元素序列为：Al2O3→SiO2→P→Ti→La→Fe2O3→Th→Zr→Nb→Y→U。利用豫西熊耳山地区安山岩风化剖面、残坡积—沟系土剖面、化探详查水系沉积物和区域化探水系沉积物4种比例尺尺度的样品对构建的岩性地球化学基因进行了检验,结果发现岩性地球化学基因在风化过程中具有很好的遗传性(从岩石到风化产物)和继承性(从土壤到其源岩),利用岩性地球化学基因可以对土壤样品进行物源示踪。源自同一母岩的水系沉积物和土壤之间在岩性地球化学基因方面具有很好的相似性(同源风化产物之间)。基于中国区域化探水系沉积物调查数据,可以构建岩性地球化学基因库来对岩石及其风化产物样品进行溯源分析,在地质、环境、法庭等科学领域具有潜在应用前景。     

Geochemistry, Petrology and Mineralogy of Coal Measure Shales in the Middle Jurassic Yanan Formation from Northeastern Ordos Basin, China: Implications for Shale Gas Accumulation

The Jurassic Yanan Formation is one of the most important coal-producing formations and hydrocarbon source rocks in the Ordos Basin, North China. To evaluate the shale gas potential of the Yanan shale, a total of 48 samples from north Ordos Basin were sampled, and their geochemical, petrological, mineralogical and pore characteristics were investigated. It was found that the shale samples are a suite of early mature source rock. The total organic carbon (TOC) content ranges from 0.33% to 24.12% and the hydrogen index (HI) ranges from 43.31mg/g to 330.58 mg/g. The relationship between Tmax and HI indicates the organic matter is type Ⅱ-Ⅲ. This conclusion is also supported by the organic petrological examination results, which shows that the kerogen is mainly liptinite and vitrinite. Minerals in the samples are composed mainly of quartz, clay and feldspar, and the clay minerals are composed of prevailing kaolinite, illite/smectite, chlorite and a small amount of illite. Under scanning electron microscope, OM pores in the Yanan shale are scarce except pores come from the kerogen intrinsic texture or clay aggregates within the organic particles. As the weak compaction caused by shallow burial depth, interparticle pores and intraparticle pores are common, the hydrocarbon storage capacity of the Yanan shale was improved. According to evaluation, the Yanan shale is considered as a good shale gas reservoir, but its hydrocarbon potential is more dependent on biogenic and coal-derived gas as the thermogenic gas is limited by the lower thermal maturity.     

Change in carbon flux (1960–2015) of the Red River (Vietnam)

Global riverine carbon concentrations and fluxes have been impacted by climate and human-induced changes for many decades. This paper aims to reconstruct the longterm carbon concentrations and carbon fluxes of the Red River, a system under the coupled pressures of environmental change and human activity. Based on (1) the relationships between particulate and dissolved organic carbon (POC, DOC) or dissolved inorganic carbon (DIC), and suspended sediments (TSS) or river water discharge and on (2) the available detailed historical records of river discharge and TSS concentration, the variations of the Red River carbon concentration and flux were estimated for the period 1960–2015. The results show that total carbon flux of the Red River averaged 2555?±?639 kton C year^?1. DIC fluxes dominated total carbon fluxes, representing 64% of total, reflecting a strong weathering process from carbonate rocks in the upstream basin. Total carbon fluxes significantly decreased from 2816 kton C year^?1 during the 1960s to 1372 kton C year^?1 during the 2010s and showed clear seasonal and spatial variations. Organic carbon flux decreased in both quantity and proportion of the total carbon flux from 40.9% in 1960s to 14.9% in 2010s, reflecting the important impact of dam impoundment. DIC flux was also reduced over this period potentially as a consequence of carbonate precipitation in the irrigated, agricultural land and the reduction of the Red River water discharge toward the sea. These decreases in TSS and carbon fluxes are probably partially responsible for different negatives impacts observed in the coastal zone.     

Experimental study on excavating strip coal pillars using caving zone backfill technology

Strip mining was the major method to control surface subsidence when mining under buildings in China; however, its coal recovery ratio was only 30 to 50%, resulting in a large amount of coal resource waste due to the retained strip coal pillars. As such, it is of important significance to recover the retained pillars while guarantee the safety of the buildings at surface. In order to address this issue, excavating strip coal pillars using caving zone backfill technology was proposed in this study. The process of this technology was to grouting backfill the original strip caving zones using high-water content material at first, creating a combined backfill body of caved gangue and high-water content material, the backfill body acted as the temporary support. Then the retained pillars were excavated and the newly produced caving zones were backfilled with one interval, which effectively prevented the movement and deformation of the strata. The backfilling system and technology were designed and trailed to excavate the retained pillars at mining area 911 in Bucun colliery. It was found that the backfilling rate reached 96.8 to 98.7% in the original caving zones, the backfilling body in caving zones was highly compacted, and the maximum surface subsidence was only increased to 67 mm with no growth in the failure depth of floor. The retained coal pillars in three of the mining areas were safely excavated and the safety of buildings on the ground was preserved.     

LNAPL污染物及水含量对石英砂介电常数的影响

为研究LNAPL污染物及水含量对石英砂介电常数的影响,首先以石英砂模拟单一土壤环境,利用柴油和水的混合物来模拟轻非水相液体(LNAPL)污染物污染土壤,然后通过矢量网络分析仪和开口同轴探头,分析高频超宽带电磁波在土壤中的反射并计算介电常数。实验结果显示,石英砂介电常数随着体积含水量和含油量的增加而增加,直到达到饱和状态,此时石英砂介电常数趋于稳定;石英砂介电常数实测值处于极化模型和De Loor模型之间,结果与De Loor模型接近。     

Fluid Inclusion and Carbon-Oxygen Isotope Studies of the Hujiayu Cu Deposit, Zhongtiao Mountains, China: Implications for Syn-metamorphic Copper Remobilization

The Hujiayu Cu deposit,representative of the "HuBi-type" Cu deposits in the Zhongtiao Mountains district in the southern edge of the North China Craton,is primarily hosted in graphitebearing schists and carbonate rocks.The ore minerals comprise mainly chalcopyrite,with minor sphalerite,siegenite[(Co,Ni)_3S_4],and clausthalite[Pb(S,Se)].The gangue minerals are mainly quartz and dolomite,with minor albite.Four fluid inclusion types were recognized in the chalcopyrite-pyrite-dolomite-quartz veins,including CO_2-rich inclusions(type Ⅰ),low-salinity,liquid-dominated,biphase aqueous inclusions(type Ⅱ),solid-bearing aqueous inclusions(type Ⅲ),and solid-bearing aqueous-carbonic inclusions(type Ⅳ).Type I inclusion can be further divided into two sub-types,i.e.,monophase CO_2 inclusions(type Ⅰa) and biphase CO_2-rich inclusions(with a visible aqueous phase),and type Ⅲ inclusion is divided into a subtype with a halite daughter mineral(type Ⅲa) and a subtype with multiple solids(type Ⅲb).Various fluid inclusion assemblages(FIAs) were identified through petrographic observations,and were classified into four groups.The group-1 FIA,consisting of monophase CO_2 inclusions(type Ⅰa),homogenized into the liquid phase in a large range of temperatures from-1 to 28℃,suggesting post-entrapment modification.The group-2 FIA consists of type Ⅰb,Ⅲb and Ⅳ inclusions,and is interpreted to reflect fluid immiscibility.The group-3 FIA comprises type Ⅱ and Ⅲa inclusions,and the group-4FIA consists of type Ⅱ inclusions with consistent phase ratios.The group-1 and group-2 FIAs are interpreted to be entrapped during mineralization,whereas group-3 and group-4 FIAs probably represent the post-mineralization fluids.The solid CO_2 melting temperatures range from-60.6 to56.6℃ and from-66.0 to-63.4℃ for type Ⅰa and type Ⅳ inclusions,respectively.The homogenization temperatures for type Ⅱ inclusions range from 132 to 170℃ for group-3 FIAs and115 to 219℃ for group-4 FIAs.The halite melting temperatures range from 530 to 562℃ for typeⅢ b and Ⅳ inclusions,whereas those for type Ⅲa inclusions range from 198 to 398℃.Laser Raman and SEM-EDS results show that the gas species in fluid inclusions are mainly CO_2 with minor CH_4,and the solids are dominated by calcite and halite.The calcite in the hosting marble and dolomite in the hydrothermal veins have δ~(13)C_(V-pdb) values of-0.2 to 1.2‰ and-1.2 to-6.3‰,and δ~(18)O_(v-smow) values of 14.0 to 20.8 ‰ and 13.2 to 14.3‰,respectively.The fluid inclusion and carbon-oxygen isotope data suggest that the ore-forming fluids were probably derived from metamorphic fluids,which had reacted with organic matter in sedimentary rocks or graphite and undergone phase separation at 1.4-1.8 kbar and 230-240℃,after peak metamorphism.It is proposed that the Hujiayu Cu deposit consists of two mineralization stages.The early stage mineralization,characterized by disseminated and veinlet copper sulfides,probably took place in an environment similar to sediment-hosted stratiform copper mineralization.Ore minerals formed in this precursor mineralization stage were remobilized and enriched in the late metamorphic hydrothermal stage,leading to the formation of thick quartz-dolomite-sulfides veins.     

Reassessment of Hydrofluoric Acid Desilicification in the Carius Tube Digestion Technique for Re–Os Isotopic Determination in Geological Samples

In this study, Re and Os isotopes were systematically determined in six geological reference materials (RMs; covering a wide range of lithologies) using the Carius tube (CT) digestion technique with and without hydrofluoric acid desilicification. Our results show that the HF desilicification increased the Re extraction efficiency (by 9–15%) evidenced from basaltic and andesitic rocks (e.g., BHVO‐2, TDB‐1 and AGV‐2). This implies that a small proportion of Re resides in silicate phases. For mafic–ultramafic rocks (e.g., BCR‐2, WGB‐1 and WPR‐1), Re extraction efficiencies obtained by the CT digestion with and without HF desilicification were similar. This may indicate that Re in these rocks may dominantly reside in some phases (e.g., magnetite and sulfides) that could be completely dissolved in aqua regia solutions without the aid of HF desilicification. Our results also show that the HF desilicification increased Os extraction efficiency (by 13–99%) in some RMs (e.g., BHVO‐2, WGB‐1 and AGV‐2). This observation suggests that a portion of Os‐rich trace phases may occur as inclusions in the silicate phases that act as isolators at ~ 200 mesh sizes. This study demonstrates that the HF desilicification step prior to CT digestion is important for complete extraction of Re and Os in geological samples.     

春季中国东海黑潮区大气热源异常对中国东部降水的影响

采用ERA-interim逐日再分析数据集与中国东部389个站逐日降水资料,通过相关和合成分析讨论了不同时间尺度上,春季中国东海黑潮区上空大气热源异常对东亚大气环流和中国东部降水的影响。观测分析表明,春季中国东海黑潮区上空为一显著的大气热源,大气对该热源的响应在不同时间尺度上表现出不同的形式。在较长时间的季节和年际尺度上,春季中国东海黑潮区大气热源增强时,可在大气对流层低层强迫出偏南气流,同期春季及后期夏季西太平洋副热带高压增强并西伸,相比于热源低值年西北太平洋副热带地区为一反气旋式异常环流所控制,中国长江中下游以南地区降水增多;反之亦然。与年际和季节时间尺度不同,在较短的天气时间尺度上,中国东海黑潮区上空大气热源增强可在其下方强迫出气旋式异常环流。大气热源的增强与中国东部对流层低层气旋式异常环流的东移有关,相应地在中国东部地区出现了显著的降水增多。     

造山型金矿床成矿过程研究进展

造山型金矿床形成在汇聚板块边缘挤压或压扭的构造环境中,其形成时间和空间与造山作用过程存在成因上的联系。造山型金矿床是全球重要的金矿类型,为世界提供了1/3的黄金储量。该类型金矿床能和造山带演化及超大陆拼合紧密联系在一起,是现代矿床学研究的热点之一。文章回顾了近十余年造山型金矿床成矿过程研究的成果,以矿床学三大基本问题源、运、储为框架,归纳总结了前人对造山型金矿床的认识,深入分析了造山型金矿床的成矿流体特征、金和硫的来源及含矿流体迁移过程和金的沉淀机制,对比分析了地壳连续成矿模式和变质脱流体成矿模式,探讨了造山型金矿床时空分布与陆壳生长的联系,最后梳理了造山型金矿床成矿过程研究中存在的科学问题和新认识。目前对造山型金矿床的主要认识有:1成矿流体以变质流体为主,金元素和矿化剂硫最有可能来自沉积地层内;2金发生高效沉淀的关键因素是流体压力骤降,而不是流体温度降低;3在高级变质作用峰期条件下能否同时发生金矿化作用是地壳连续成矿模式和变质脱硫体成矿模式的最大分歧点;4造山型金矿床的时空分布规律与超大陆拼合过程有关。