Petrogenetic character and provenance of metabasalts in the aspiring and Torlesse Terranes, South Island, New Zealand: Implications for the gold endowment of the Otago Schist?

We report quantitative X-ray diffraction, whole-rock geochemical and Sm–Nd isotope data for metabasalts from the Aspiring and Torlesse Terranes in the South Island of New Zealand. These rocks underlie the Mesozoic metasedimentary Otago Schist which is anomalously enriched in gold and host to at least one world-class orogenic gold deposit at Macraes (> 125 t Au). Geochemical and Nd isotopic similarities between the samples point to a common history of the two terranes rather than the amalgamation of one or two allochthonous plate fragments. Furthermore, geochemical and Nd data suggest the metabasalts within both terranes formed in an oceanic but essentially non-subduction-related setting. The origin of the Aspiring and Torlesse basalts can be linked to the formation of an oceanic plateau that had resulted from a (?Permian) mantle plume initiation event proximal to a mid-oceanic rise or triple junction. Given the intrinsically gold-enriched nature of certain oceanic-character mafic rocks, the anomalous gold endowment of the Otago Schist may have been enhanced via the accretion and subduction of a gold-enriched oceanic plateau fragment. The metabasalts are generally enriched in gold (up to 13 ppb) compared to their enclosing metasedimentary rocks (typically ca. 1 ppb), with sulphide-rich metabasaltic rocks having up to 550 ppb Au. However, the relatively small volume of metabasalts in the Otago Schist precludes these rocks as the principal source for Otago Schist orogenic gold, with a primarily metasedimentary source of the gold potentially having a limiting effect on the overall endowment of the Otago Schist. This approach, that employs petrogenetic fingerprinting of potentially fertile source rocks for the assessment of gold endowment, might prove useful in the conceptual exploration targeting of relatively immature and poorly exposed terrains.     

氦气的天然气地质意义

氦气具有的不易液化、稳定性好、扩散性强等特点,使它既能在天然气藏中富集,又能垂向运移至地表。氦有大气氦、壳源氦和幔源氦3种来源。3He主要来源于地幔;4He主要来源于地壳,通常以R/Ra来表示氦的来源。氦气具有丰富的天然气地质意义：地表氦气浓度异常有一定油气指示意义;氦气的同位素分布特征值（R/Ra）还具有指示油气构造环境、指示断裂带及旁证CO2气藏的成因等地质意义。     

Tomographic imaging of hydrated crust and mantle in the subducting Pacific slab beneath Hokkaido, Japan: Evidence for dehydration embrittlement as a cause of intraslab earthquakes

We estimate detailed three-dimensional seismic velocity structures in the subducting Pacific slab beneath Hokkaido, Japan, using a large number of arrival-time data from 6902 local earthquakes. A remarkable low-velocity layer with a thickness of ~ 10 km is imaged at the uppermost part of the slab and is interpreted as hydrated oceanic crust. The layer gradually disappears at depths of 70–80 km, suggesting the breakdown of hydrous minerals there. We find prominent low-velocity anomalies along the lower plane of the double seismic zone and above the aftershock area of the 1993 Kushiro-oki earthquake (M7.8). Since seismic velocities of unmetamorphosed peridotite are much higher than the observations, hydrous minerals are expected to exist in the lower plane as well as the hypocentral area of the 1993 earthquake. On the other hand, regions between the upper and lower planes, where seismic activity is not so high compared to the both planes, show relatively high velocities comparable to those of unmetamorphosed peridotite. Our observations suggest that intermediate-depth earthquakes occur mainly in regions with hydrous minerals, which support dehydration embrittlement hypothesis as a cause of earthquake in the subducting slab.     

织金洞洞穴环境变化及成因分析

对比和拟合分析1989年、2011-2013年和2015-2016年织金洞内气候环境因子监测数据以及游客量数据发现:织金洞自开发初期至今,洞内CO2浓度和温度水平增高明显,增加幅度分别可达1 000 ppm和2～3 ℃,而2011-2013年与2015-2016年间CO2差值最大达465 ppm。洞内环境变化的最主要因素是旅游活动和人工光源;游客量从1985年的不足5万人增至2015年的59.457 1万人,洞内CO2浓度总体上呈现出随着时间增加而不断增高的趋势;各年份气温差距不大,但总体上仍展现出逐年降低的趋势,湿度除2011年外,差距并不明显;人工光源产生的温度与环境温度最大温差可达33 ℃,湿度和周边环境的湿度最大差值可达66.7%。      

Thirty Years of the Seafloor CORK Borehole Observatories: Development,Applications and Future Perspective

In the past 50 years, we have witnessed remarkable progress in our understanding of the Earth and ocean system, as a result of the internationally integrated deep ocean drilling programs, the Deep Sea Drilling Program (DSDP), the Ocean Drilling Program (ODP), and the Integrated Ocean Drilling Program (IODP). One of the legacies of the deep ocean drilling programs is the development and applications of the CORK, Circulation Obviation Retrofit Kit. Earth and ocean sciences have been shifting from a traditional discontinuous, expeditionary mode toward a mode of sustained in situ observations today. The seafloor CORK observatories offer Earth, ocean and life scientists new opportunities to study multiple, interrelated deep marine subsurface processes, over time scales ranging from seconds to decades. Here, we first provided a concise examination of the development history of the CORKs, then described the first installations of ODP CORKs, the evolution of different models of CORK, and finally, summarized the scientific lessons learned in the installation and operation effort of the CORKs. In the end, we offered our perspectives on using CORKs to study geological, hydrogeological, microbiological, and biogeochemical processes in the deep marine subsurface biosphere, particularly pertaining to China’s efforts in establishing and enhancing its deep-sea and deep-biosphere research and monitoring programs.     

Distribution,Compositions and Significance of Oceanic Red Beds

Oceanic red beds are widely distributed in the global oceans and across the entire Phanerozoic period, which mostly appeared after oceanic anoxic events. They represent typical oxygen-rich sedimentary environment and play a significant role on ocean science research. Numerous studies have been carried out since the oceanic red beds were discovered. However, previous studies mainly focused on the Cretaceous oceanic red beds, and the understanding of the characteristics and scientific significance of oceanic red beds are not comprehensive. Therefore, we here summarized the global distribution characteristics and compared mineral and element compositions of various lithological oceanic red beds, including marly, clayey and cherty oceanic red beds. The main mineral and element components of oceanic red beds have no direct relationship with the color of the sediments, and mainly are affected by the regional environment and provenances. Therefore, the mineralogical and geochemical characteristics of oceanic red beds should be analyzed in combination with the regional background. The red coloration of oceanic red beds is controlled mainly by hematite, goethite and manganese-bearing calcite, which have two main mechanisms: ① Colored minerals formed in oxic conditions; ② Colored minerals formed due to low deposition rates. These two mechanisms are not completely independent, but complement one another with either dominance in most oceanic red beds. Lithological characteristics of oceanic red beds are controlled by three factors, including water depth, productivity and nutrients. Therefore, the formation of oceanic red beds should be considered with global changes and regional events. The unique origin mechanism and global distribution characteristics of long time-scale oceanic red beds can be used to indicate sedimentary paleoenvironment, paleo-oceanic current, and paleoclimate change. In addition, hydrothermal or magmatic activities on the ocean floor could also produce red-color deposits that are strongly different from sedimentary oceanic red beds. Based on the existing research, we also put forward the future in-depth studies on the oceanic red beds from multidisciplinary perspectives.     

页岩储层-超临界CO2-模拟压裂液相互作用实验研究及其环境意义

近年来,页岩气作为一种重要的非常规天然气来源,逐渐成为国内外关注的热点。当前的研究工作总体侧重于页岩气开采技术的改进与环境监测,对页岩气开采过程中水岩相互作用还少有报道。本文采用模拟实验,选取储层页岩样品,在温度90 ℃、压力10 MPa环境下,开展了CO2压裂液页岩相互作用实验研究。主要探讨页岩气开采过程中,由于常规水力压裂液以及后期超临界CO2的增注,造成的储层岩石矿物的变化以及返排液成分的变化。实验结果显示：压裂液能使岩石矿物发生溶蚀,超临界CO2的存在会进一步加剧溶蚀反应的进行,促使孔隙变大并产生更多的微孔隙,为页岩气提供更多的运移通道,有利于油气的运移。但是,存在的环境威胁不容忽视：一方面,岩石中会溶解出大量的Ca、Mg、Si元素和少量Fe、Mn等金属元素,超临界CO2、富有机质页岩以及压裂液中表面活性剂等物质在高温高压酸性环境条件下,容易生成挥发性有机物残留在地层中,极有可能沿着岩石破碎的孔隙、断裂发生迁移或泄露,从而对地下含水层造成污染;另一方面,多种成分进入高矿化度溶液体系经返排回到地表,也会增大处理返排液的难度。本文取得的实验数据和成果有助于理解页岩气储层在开采过程中可能发生的水岩相互作用过程及其潜在的环境风险。     

岩浆泡破裂引发地震的模式——以吉林松原2013年地震群为例

2013年10月31日,吉林省松原前郭尔罗斯蒙古族自治县（44.60°N,124.18°E）发生震级为5.5级地震,此后的40 d内发生了700多次地震,其中5级以上地震5次。松原地区近年来地震活动频繁,2014年1月以来又发生4级以上地震9次、5级以上地震1次,震中处于松辽盆地油气田开采区,地震活动序列十分特殊。为了揭示松原地震的发震机制与发震模式,研究深部地质过程与地震的关系,根据此次实测的通过震中25 km长的大地电磁测深剖面,结合地热梯度、He同位素比值（³He/⁴He）、CO₂碳同位素、地震序列等资料的综合分析,发现震中地区存在两个位于不同深度的低阻体,地震发生与地幔深部岩浆活动有关;据此提出了一种新的地震发生模式——岩浆泡破裂发震模式,描述了来自地幔的基性岩浆通过向上侵入、在脆-韧性转换带附近聚集形成岩浆泡、岩浆泡破裂及岩浆泡上覆岩层中聚集能量引发岩层破裂产生地震的过程,并使来自地幔的无机成因的CO₂气在储层中形成CO₂气藏。该模式可以解释许多发生在大陆内部地震和深源地震的发生机制。     

非潮汐海洋运动对地球动力学扁率变化的贡献

通过考察全球海洋环流数值模型以及TOPEX/Poseidon海洋测高数据,得到结论：1997/1998年后的部分J2异常变化可能来自海洋环流变化导致的质量重新分布,具体地说是太平洋环流变化导致的从高纬地区向低纬地区的质量迁移. 本工作表明来自于海洋内部温盐效应的变化对J2异常变化有重要贡献,进一步证实了卫星激光测距资料所得结果的可靠性.