New Macroscopic Problematic Fossil from the Early Cambrian Yanjiahe Biota,Yichang, Hubei,China

Yanjiahella gen. nov., a distinctive fossil taxon from the Early Cambrian Yanjiahe Biota in Yichang, Hubei Province, is characterized by: 1) an overall body plan composed of a stalk and a calyx (also arms in some species); 2) a stalk with closely spaced, transverse wrinkles and a medial, longitudinal ridge; and 3) a calyx preserved with three-dimensional radiating striations, as well as a probable madreporite in some specimens. Three species that can be assigned to this genus, which are Y. ancarpa sp. nov., Y. monocarpa sp. nov., and Y. biscarpa sp. nov. Yanjiahella is comparable to certain echinoderm taxa in terms of morphology and some biological structures, which might indicate the early evolution and diversification of ancestral echinoderm lineages from the early Early Cambrian Yangtze Platform. The discovery of putative echinoderms in the Yanjiahe Biota provides significant clues about the origination and evolution of the deuterostome phylum Echinodermata.     

山东玲珑和郭家岭岩体的同位素年龄及其地质意义

本文采用~(40)K-Ar/~(39)Ar快中子活化和K-Ar稀释法定年技术对玲珑岩体和郭家岭岩体进行了年龄测定。~(40)Ar/~(39)Ar阶段加热年龄谱表明,玲珑岩体和郭家岭岩体的坪年龄分别为164.2±0.7Ma和134.8±1.7Ma,其形成时代同属燕山期,为同一成因不同阶段的产物。同位素年龄提供的数据支持了两岩体为交代混合岩化的成因观点。~(40)Ar/~(39)At和K-Ar年龄结果还表明:角闪石和黑云母均是~(40)Ar/~(39)Ar理想定年矿物,对K-Ar法而言,角闪石最理想,黑云母次     

山西南部上古生界煤层含气性研究Ⅲ.煤层气采收潜势分析

采用直接解吸法、等温吸附法和吸附-解吸法,对研究区上古生界主煤层中煤层气的采收潜势进行分析,得出了一些有意义的结论:在0.7MPa废弃压力水平,推定区中绝大部分矿区的主煤层将可能没有煤层气产出;推断-预测区主煤层的采收潜势以临汾盆地最好,沁源东-安泽和沁水-翼城地区上主煤层也相对较高,而下主煤层普遍较差或极差。     

Geochemical Evolution of Hydrothermal Fluids at the Daejang Cu–Zn–Pb Vein Deposit, Korea

Abstract: The Daejang mine is located within the Cretaceous Gyeongsang basin. Mineral paragenesis can be divided into four stages (stages I, II, III and IV) by major tectonic fracturing. Stages I, III and IV are economically barren. Stage II, at which the precipitation of major ore minerals occurred, is further divided into three substages with paragenetic time based on minor fractures and discernible mineral assemblages: substage IIa, marked by deposition of quartz and Fe–sulfides; substage IIb, by introduction of base-metal sulfides within carbonates and some quartz; substage IIc, by quartz and carbonates with various sulfosalts. Fluid inclusion data indicate a complex geochemical evolution of hydrothermal fluids. Both CO₂–rich and H₂O–rich fluids were trapped in fluid inclusions at stage I and substage IIa. It is suggested that a compositionally heterogeneous fluid was formed by fluid boiling and CO₂ immiscibility at temperatures of about 400° to 300°C. Composite lodes of base-metal sul–fides, carbonates and quartz at substage IIb were deposited in open spaces created by fracturing. The fracturing event prompted rapid decreases in pressure and temperature of residual fluids and resulted in retrograde fluid boiling at about 200 bars and 300°–250°C during substage IIb. The progressive loss of CO₂ by CO₂ effervescence and retrograde boiling from substage IIa and IIb fluids resulted in pH increase and related increase in carbonate activity, causing deposition of abundant carbonates. The change in pH also caused the decrease of stability of hydrogen sulfide with Cu, Zn and Pb chloride complexes (as main transporting agents at Daejang) and resulted in the pricipitation of base-metal minerals. Deposition of Ag– and Sb-bearing sul–fides and sulfosalts of substage IIc occurred at temperatures of about 250° to 150°C from a dominantly aqueous fluid with low salinity (down to 3. 0 equiv. wt % NaCl). At this substage, aqueous fluid formed by mixing with cooler and less saline meteoric groundwater. There is a systematic decrease in caculated δ¹⁸O_water values with the mineralization stage (and decreasing temperature) in the Daejang hydrothermal system, from values of about 11% for stage I, through about 4% for stages II and III, to about –3 per mil for stage IV. The result of stable isotope and fluid inclusion studies are interpreted to indicate progressive less evolved and/or unexchanged meteoric water influx of an early hydrothermal system formed by highly evolved meteoric waters.     

Post-subduction margin structures along Boyd Strait, Antarctic Peninsula

The Pacific margin of the Antarctic Peninsula to the southwest of the Hero Fracture Zone (HFZ) is a former subducting margin which became inactive following the arrival of ridge crest segments of the Antarctic–Phoenix ridge at the margin during the Tertiary. In contrast, the part of the margin to the northeast of the HFZ remains active. Tertiary convergence was approximately perpendicular to the margin and ongoing motion is thought to have the same orientation. A new seismic reflection profile running along Boyd Strait, just northeast of the landward projection of the HFZ, shows major structural components similar to those typically observed along the margin to the southwest of the HFZ. In order of increasing proximity to the margin, these components are: the inner shelf, the shelf basin, the mid-shelf basement high (MSBH), and the outer shelf. The continuation of the post-subduction margin structures to the active margin suggests that the boundary between crust with passive and active margins characteristics is not sharply defined. Our postulated scenario for tectonic evolution along Boyd Strait is that: (1) before the arrival of the last ridge crest segment to the southwest of the HFZ, the inner shelf and the shelf basin were part of a Cretaceous–Tertiary arc and forearc area, (2) after the arrival, thermal effects resulting from interaction of the ridge crest with the margin just southwest of the HFZ lead to the formation of the MSBH to the northeast, but MSBH uplift in Boyd Strait did not prevent concurrent cross-shelf sediment transport contributing to development of an extensive outer shelf on the seaward flank of the MSBH, (3) Recent extension in Bransfield Strait, a marginal basin to the northeast of the landward projection of the HFZ, has caused about 10 km of seaward deflection in the strike of the part of the MSBH to the northeast of the projection of the HFZ.     

滇西金满脉状铜矿床的40Ar-39Ar快中子活化年龄

金满铜矿床是滇西兰坪——思茅盆地中-新生代砂页岩中相当典型的脉状矿床。关于该矿床的成矿时代,多年来一直沿用铅同位素模式年龄,缺乏更为可靠的同位素年龄数据,因而对该矿床乃至盆地内同类矿床成矿作用的认识带来了很大困难。为探讨该矿床的形成时代,作者选取含铜石英脉状矿石中的石英进行⁴⁰Ar-³⁹Ar快中子活化年龄分析。     

沁水盆地南部煤层气井增产的储层生产控制探讨

以沁水盆地南部区块煤层气生产井的工程、测试、监测数据为依据,对影响煤层气井产能的储层生产控制因素进行了分析,探讨了优化储层生产控制、提高煤层气井产能的工程措施,重点研究了水力压裂工艺施工参数与煤层气井产能的关系,提出了有利于提高煤层气井产能的水力压裂工艺施工参数。结果表明：合理控制钻井液的密度与粘度,可提高煤层气井的产能;煤层气井的产能与固井工艺中的水泥浆密度与用量呈现负相关关系;水力压裂采用变砂比、控制压裂液、变排量等施工工艺和优化的工艺参数值可有效提高煤层气井气产量。     

溧阳戴埠火山岩开放体系岩浆活动探讨

戴埠下火山岩系层序—岩相—成分演化之间关系研究表明,火山产物是从十个喷发中心经深部岩浆脉动式补充、快速分异、间歇式喷发所形成。第一和第二旋回之间具沉积间断,而且喷发中心迁移与新生岩浆补充相对应。在两个旋回内部,中性和酸性喷发产物都具宽的或较宽的成分范围和快速分异特点。中性溢流相之后,从中酸性火山屑碎流相至酸性溢流相或侵出相的喷发强度降低,是岩浆房萃取深度降低的结果。分离结晶和同化作用是岩浆演化的主要原因。     

干旱草原覆盖区非矿致化探异常的识别与解释—以内蒙古洪根尼乎都格草原D2选区为例

受自然因素的影响,干旱草原覆盖区化探异常往往存在多解性和不确定性,如何对非矿致化探异常进行有效识别和解释对降低勘探风险具有极为重要的现实意义。内蒙古洪根尼乎都格干旱草原景观覆盖区(D2选区)为乌日尼图式找矿预测重点验证区。通过1∶2.5万的常规化探工作,在该区内发现了明显的Cu、Mo、W异常。结合已有的化探资料,以及典型土壤样品主微量元素测试,矿物成分分析,Cu、Mo相态分析的结果,对该覆盖区覆盖物的物源进行了初步判断并研究了重点成矿元素Cu、Mo的异常成因:发现Cu、Mo异常区与背景区内覆盖物来源有明显差异,判断该区Cu、Mo异常为非矿致异常。同时在此研究基础上提出了在覆盖区化探工作中识别与解释非矿致异常的思路和方法。     

1981—2022年藏东南4种界限温度时空变化

基于1981—2022年藏东南（林芝市）4个气象站点的日平均气温数据,采用线性倾向估计、Person系数、Mann-Kendall检验、优势主导分析等方法,分析了藏东南≥0 ℃、≥5 ℃、≥10 ℃和≥15 ℃共4种界限温度的时空变化特征。结果表明：(1)受海拔影响,藏东南4种积温总体呈自东南向西北递减的变化特征,各地≥0 ℃、≥5 ℃、≥10 ℃和≥15 ℃积温分别介于3161.4~4429.9 ℃·d、2869.2~4018.0 ℃·d、2273.3~3258.0 ℃·d和608.8~2133.2 ℃·d。(2)近42 a藏东南4种界限温度均呈初日提前、终日推迟、持续日数延长的趋势,≥10 ℃界限温度变幅最小,除初日外,≥15 ℃界限温度变幅最大。≥0 ℃和≥5 ℃持续日数的延长主要是初日提前引起的,≥10 ℃与≥15 ℃持续日数的增加主要是终日推迟导致的。4种积温均表现出极显著的增加趋势,增幅分别为123.81 ℃·d/10 a、136.71 ℃·d/10 a、76.22 ℃·d/10 a、166.43 ℃·d/10 a。(3)年代际变化上,4种积温具有明显的逐年代际增加态势。21世纪10年代是研究时段内最温暖的10 a,这一时期的4种积温比20世纪80年代增加了174.9~437.2 ℃·d,其中≥15 ℃积温增幅最大。除≥10 ℃外,20世纪80—90年代初日推迟、终日提早、持续日数缩短,而21世纪前20 a则截然相反。(4)M-K检验显示,≥10 ℃初日、终日未发生气候突变,其他界限温度指标发生突变时间多在2004年前后。