河套盆地北缘色尔滕山河流地貌参数特征及其成因分析

地貌形态是构造和地表过程相互作用的复杂产物,主要通过构造活动和岩石的抗侵蚀能力等来调节。构造活动相对较弱的古老造山带往往可以忽略构造驱动的岩石抬升,使得研究岩石抗侵蚀能力对其地貌雕刻的贡献成为可能。但是目前大多数活动造山带地貌研究的结果显示地貌主要受控于活动构造,关于岩性对地貌演化影响的报道较少。色尔滕山山前断裂为河套盆地北缘的一条重要控盆断裂,全新世以来该断裂的活动性较强,曾发生过两次较大震级地震（M6. 4和M5. 9）。前人活动构造研究表明该断裂的活动性具有空间差异,中部乌加河镇活动性最强,两端逐渐减弱。但相对河套盆地北缘其他大型断裂（如狼山山前断裂、乌拉山北缘断裂和大青山山前断裂）,该断裂的地貌参数研究较少。同时其地貌演化特征及发育机理仍然不清楚,这些均制约了对该断裂的变形动力学理解。本文基于30 m分辨率的DEM数据对该断裂进行详细的河流地貌学参数研究,包括使用Arcgis和Matlab脚本提取色尔滕山山前33条河流的子流域盆地面积 高程积分（HI）和相应河道陡峭指数（Ksn）、河道纵剖面及其裂点等地貌学参数。结果表明研究区河流HI值大部分处于0. 40~0. 66之间,其中乌加河镇附近具有高值,流域盆地处于发育的壮年期。瞬态河道和稳态河道均沿着色尔滕山山前断裂走向分布,可能表明色尔滕山山前大部分河道目前处于瞬时地貌向均衡地貌演化阶段,并且通过对比发现瞬态河道裂点成因存在岩性和构造共同控制的现象。河道陡峭指数空间分布差异性较大,乌加河镇附近（S13~S20）陡峭指数较大,向两边陡峭指数逐渐减小,在S8河流以西又有增大的趋势。通过结合岩性和降雨情况分析发现,河道陡峭指数除了受岩性抗侵蚀能力影响外,其分布还与色尔滕山山前断裂垂直滑移速率分布和垂直位错分布基本一致。综合来看,地貌参数的空间分布是岩性差异和色尔滕山山前断裂活动分段差异性共同控制的结果,表明该地区岩性和构造对地貌的协同塑造作用。     

Pollution of Osheepcheon Creek by abandoned coal mine drainage in Dogyae area,eastern part of Samcheok coal field,Kangwon-Do,Korea

Osheepcheon Creek running through the Dogyae area is being polluted by the influx of the abandoned coal mine drainage. Generally, the more polluted water has lower pH and Eh and higher conductivity values. The concentrations of Mg, Ca, Fe, SO₄, and some trace elements, such as Cd, Co, Cr, Mo, Ni, Pb, Rb, Sr, U and Zn, are tens to hundreds of times more concentrated in the abandoned coal mine drainage than in the unpolluted streamwater. However, most immobile toxic pollutants from the mine drainage are quickly removed from the streamwater by the precipitation of amorphous Fe hydroxide and sorption on the precipitated Fe hydroxide. The fast removal of the pollutants from the streamwater maintains the water quality of the creek as acceptable at most places along the stream path, except where the abandoned coal mine drainage flows in. However, the creek has the potential of deteriorating quickly if the mine drainage is allowed to be continuously combined with the streams. A function of pH, Eh, and conductivity has been developed with discriminant function analysis for the purpose of easy, fast, and inexpensive measurement of the degrees of pollution of the streams. The estimated pollution of the streams with the discriminant function are consistent with what the chemical compositions of the water samples indicate. The pollution map of the study area was constructed from the calculated scores with the discriminant function. The pollution map suggests that the pollutants mainly come from the west side of Osheepcheon Creek. Thus, the abandoned coal mine drainage from the west side has to be appropriately treated as soon as possible to prevent Osheepcheon Creek from being further polluted. Considering the topography, climate, and the amount of the mine drainage, an active treatment method is recommended.     

大渡河上游鸡心堡滑坡形成的古堰塞湖及其环境效应

堰塞湖及其溃决洪水对山地地表过程具有强烈影响, 严重危害山地区域的安全, 对堰塞湖开展相关研究, 可为区域现代堵江风险分析提供参考。以青藏高原东缘大渡河上游支流小金川鸡心堡古滑坡堰塞湖为研究对象, 采用单片再生剂量法与标准生长曲线法相结合的方法对深度约12.5m的湖相沉积剖面上的7个光释光样品测试年代, 并进行了详细的地层学与年代学研究, 恢复该堰塞湖的年代和范围, 重建该古滑坡的规模, 讨论了该古堰塞湖的成因及其环境效应。研究结果表明: 1)研究区在距今约2~3ka发生过一次滑坡堵江事件, 形成鸡心堡古滑坡堰塞湖, 持续一段时间后, 形成最大流量约为2.70×10³m³/s的洪水溃决过程; 2)该古堰塞湖的堵江残留滑坡坝高约150m, 滑坡坝面积约1.41×10⁵m², 体积约4.19×10⁶m³, 堰塞湖的面积约1.84×10⁶m², 库容水量约6.10×10⁷m³; 3)依据现有地质证据以及文献记载初步推测鸡心堡古滑坡是由地震引起的; 4)滑坡坝对现代河道的地貌形态仍然存在影响, 在滑坡坝上游形成较宽的现代河道且河道纵剖面的坡度较小, 滑坡坝后的河道陡峭指数(k_sn)较高。通过研究, 对大渡河流域的古堰塞湖有更全面、科学的认识, 为古地质灾害领域提供了一个研究实例。

     

三维古地貌重建技术在中生代羌塘地体古地理演化分析中的应用

近年来,从古地貌-沉积组合与油藏关系的角度进行油气远景评价成为研究热点。针对古地貌的复原研究,提出一种建立三维古地貌模型的方法,将二维平面古地理图通过对资料的整理、挖掘与转换,并结合GIS技术生成了三维立体模型,补充了区域地形地貌的相关信息。利用该方法,建立了青藏高原油气资源潜力最大的区域——羌塘地体在三叠纪和侏罗纪的一系列三维古地貌模型,进而对其古环境和演化过程进行分析,这对于该区域的沉积矿产资源的预测与评价有重要的参考价值。     

青藏高原周边地区河流分形特征与地貌、构造活动耦合关系

青藏高原周边地区的地貌特征与形成演化机制一直是科学界研究的热点。选择青藏高原周边典型地区河流分形特征、地貌特征及构造活动性进行研究,发现喜马拉雅断裂带、龙门山断裂带和阿尔金断裂带控制的区域构造活动性强烈,历史地震记录频繁,大震较多,河流形态与地貌演化特征也非常相似,河流纵剖面变化很快,长波长下凹型,河流坡降比大,地形起伏度大,河流形态变化简单,河流分维值低;青藏高原东北缘构造活动性不强烈,历史地震记录偏低,大震极少,河流纵剖面变化缓慢,近似长波长微振幅上凸型,河流坡降比小,地形起伏度较小,河流形态错综复杂、分维值高;青藏高原东南缘,构造活动性较强烈,历史地震记录频繁,大震较多,但由于该区域平均多年侵蚀速率比较低,同时河流下切深度大,河流纵剖面变化缓慢,也是近似长波长微振幅上凸型,河流坡降比小,河网发育较成熟,河网分维值较高。通过对比发现,降水量的变化对该区域侵蚀速率的影响远小于构造活动性的作用,在分析河网形态特征时可以不考虑降水量空间变化的影响。     

Holocene ochreous lacustrine sediments within the Famatina Belt,NW Argentina: A natural case for fossil damming of an acid drainage system

A 44 m-thick lacustrine succession of silty-clay banded ochres and subordinated sandstones, and conglomerates (known as the Corral Amarillo Formation) is superbly exposed within the Famatina Belt (Central Andes of Argentina) after deep entrenchment by the present-day Amarillo river due to strong recent uplifting and consequent relative drop in base level. The unusual ochreous-rich succession was produced by natural damming (3.48–3.54 ¹⁴C kyr BP) of an acid drainage system linked to the alteration cap of polymetallic deposits. Facies of silty-clay ochre (wet season) and banded ochre (dry season) from the paleolacustrine setting are composed of jarosite + goethite and goethite respectively. Geochemically, these layers record high concentrations of Fe₂O₃ (25–55 wt. %) and trace elements (Cu, Zn, Co, As, and Mo with mean concentrations of 2759; 2467; 109; 375 and 116 ppm, respectively). Their origin is inferred from a comparative analysis with the present-day Amarillo river, which has a pH of ∼3, (SO₄)²⁻ concentrations of ∼5000 mg/l, and jarosite as the dominant phase, in the upper catchments. Waters downstream have pH values of 3–4.5, (SO₄)²⁻ concentrations of ∼3000–480 mg/l, and schwertmannite as the dominant phase. Thus goethite in the paleolake facies is likely related to schwertmannite transformation by an aging process, whereas jarosite is probably transported from the river but could also be associated with post-depositional formation regulated by variations in grain size and the pore fluid chemistry. The Corral Amarillo Formation offers a Natural model, which may be employed to infer the effect on nature of acid drainage of mineralized areas.     

河北省唐山地区古滦河冲积扇第四纪以来演化与变迁

古滦河冲积扇研究的关注点更多在全新世,对其更新世的演化与变迁一直没有进行过系统研究。根据古滦河冲积扇上PZK10、PZK20钻孔的磁性地层学、年代地层学、沉积学、测井沉积学、岩芯色度分析等,对古滦河冲积平原的第四纪三维地质结构、冲积扇体的规模以及迁移规律进行综合研究,结果表明： PZK10孔揭露了上新世时沉积的巨厚洪积成因“泥包砾”地层,早更新世时发育两个冲积扇−湖相旋回,中更新世时发育辫状河沉积,晚更新世发育湖相、冲积扇相、辫状河相沉积。PZK20孔上新世沉积了一套巨厚“泥包砾”层,早更新世为扇前平原−辫状河相沉积,中更新世为辫状河−冲积扇相沉积,晚更新世为辫状河沉积。古滦河发育两期冲积扇,第一期为早更新世早期,在沙流河镇一带出山口形成的规模较大的冲积扇;第二期为早更新世中期,古滦河在现今丘庄水库一带发生分流,在丰润区一带出山口形成的冲积扇。中更新世,第一期冲积扇开始萎缩,第二期冲积扇继续发育,形成巨厚砾石层;晚更新世,古滦河在迁西县城以北发生袭夺,东流迁移出研究区,在西峡口进入迁安盆地,形成以西峡口为顶点的冲积扇。     

Syn-rift to post-rift tectonic transition and drainage reorganization in continental rifting basins: Detrital zircon analysis from the Songliao Basin,NE China

Tectonic transition from a syn-rift stage to subsequent post-rift stage is an important mechanism in the evolution of extensional basins. The sedimentary infill records the crustal response to this process. We have obtained new detrital zircon U-Pb and Lu-Hf signatures from the Lower Cretaceous stratigraphic successions encompassing the commonly accepted syn- to post-rift transition boundary, the T4 unconformity, in the Songliao Basin, NE China. These constrain the Songliao Basin’s evolution from its center to distal margins, providing insights into the sediment provenance and dispersal pattern over the tectonic transition. Analysis of zircons from the syn-rift (the Shahezi and Yingcheng formations) and immediate post-rift (the Lower and Middle Denglouku Formation) stages reveals Phanerozoic age populations with positive ?_Hf(t) values, which were derived from the proximal juvenile mantle-derived melt origin bedrocks of the Songliao Block. In contrast, the overlying samples from the Upper Denglouku Formation deposited in the subsequent post-rift stage contain exotic and ancient zircon populations with ages of 2.5 Ga & 1.8 Ga and complex hafnium signatures, characteristic of a mixed origin. These are interpreted to be transported from distant cratonic terranes via larger drainage networks. It is obvious that the sediment dispersal pattern switched from being a local and hydrologically closed “intraregional” pattern to a “transcontinental” pattern during the transition. The time lag between the development of the T4 unconformity and the drainage reorganization also ensures a distinguishable ～3 Myr (106103 Ma, Late Albian) transition period of regional extent. During this transition stage, syn-rift faulting was replaced by post-rift thermal subsidence, exhibiting a uniform sag configuration. Our new findings are important for understanding other continental rift basins during syn- to post-rift transition, which often demonstrates a complex interaction between the linkage and integration of sub-basins, and the reorganization of fluvial drainages and catchment systems.     

朝鲜平南盆地泥盆纪化石的发现及其地质意义

平南盆地位于中朝地台东缘朝鲜半岛中部。平南盆地古生界比较发育,特别是盆地中南部地区发育寒武系、奥陶系和志留系,仅在盆地东南部谷山、法洞地区发现了晚奥陶世到志留纪的地层,其它地区末曾发现过晚奥陶世到早石炭世的地层。最近在平南盆地中部平壤之东原中奥陶统(晚达组)上部发现了Chaetetes cf. nantanensis, Calceola sp., Thamnopora sp., Cladopora sp. 等指示泥盆纪的化石;该含化石层的走向延续性比较好,延伸长度2~3 km。基于上述研究,认为原来的中奥陶统(晚达组)上部可能为泥盆系。在中朝地台,除了西缘和西南缘地区以外,大部分地区没有发现晚奥陶世-早石炭世的地层,只有辽东太子河流域本溪组的地质时代被认定为早石炭世晚期到晚石炭世早期。这些泥盆纪、早石炭世化石都发育在中朝地台东部,说明古生代时期中朝地台西部和东部沉积环境及构造演化有差别,因而对于中朝地台古生代古地理和构造演化需要重新认识。     

胶东水系沉积物金地球化学异常分布规律及其意义

为研究巨量金聚集作用和成矿元素地球化学异常响应关系,本文针对胶东地区收集了1∶20万全国区域化探扫面计划水系沉积物、全国地球化学基准计划河漫滩沉积物和岩石的地球化学数据,绘制了该研究区水系沉积物和岩石的金地球化学分布图,并结合区域构造-蚀变-成矿特征揭示水系沉积物和主要地质体岩矿石中金的地球化学异常分布及其成因联系。研究区水系沉积物金含量以10.7×10^-9为异常下限,地球化学异常面积为164.3km^2,其中Au-1号异常面金属量占研究区总面金属量的51.94%,标准化异常面金属占研究区总标准化面金属量的73.63%,是胶东地区最主要的次生金浓集中心和原生金矿化中心,因此也是胶东金矿床密集产出的部位。区内赋矿地质体岩石、载金矿物黄铁矿和水系沉积物中成矿相关元素Au、Ag、Cu、Pb、Zn和Bi含量变化及综合对比研究表明,胶东地区不同构造带中水系沉积物金背景值受岩石金背景值和矿化体风化剥蚀的综合制约。因此,胶东金的地球化学异常图谱是由区域大规模金矿化作用、高金背景的岩石和金矿床次生风化作用相互叠加的结果,对于理解胶东金矿省巨量金聚集的地表沉积物响应和指导深部找矿勘查具有重要的参考意义。     

Touhuanping Fault, an active wrench fault within fold-and-thrust belt in northwestern Taiwan, documented by spatial analysis of fluvial terraces

This study aims at the recent activity and development of an active wrench fault, the Touhuanping Fault in northwestern Taiwan. Northwestern Taiwan has been proposed in a current situation between the mature to waning collision in terms of tectonic evolution. The main drainage in this area, the Chungkang River, flows close to the trace of the fault mentioned above. We examined various types of deformation of fluvial terraces along the Chungkang River as a key to understanding the nature and rate of the late Quaternary tectonics. The E–W trending Touhuanping Fault has long been mapped as a geological boundary fault, but its recent activity was suspected. Field survey revealed that its late Quaternary activity is recorded in the offset fluvial terraces. Our result shows dextral slip and vertical offset with upthrown side on the south, and activated at least twice since the emergence of terrace 4 (older terrace 3 with OSL date of ca. 80 ka). Total amount of offset recorded in the Touhuanping terrace sequence is 15 m for dextral and 10 m for vertical offset. Estimated recurrence time of earthquake rupture may be a few tens of thousand years. Uplift on the upthrown side of the Touhuanping Fault also resulted in the formation of drowned valleys which were graded to terrace 4. Other deformation features, such as back-tilting, westward warping, and a range-facing straight scarp, were also identified. A second-order anticline roughly parallel to the Touhuanping Fault is suggested to be the origin of the northward tilting on terrace 3; it could have resulted from a flower structure on the Touhuanping Fault at shallow depth. This may demonstrate that the buried segment of the Touhuanping Fault has also been active since 80 ka. In the northern study area, the westward warping at terrace 2 probably represents late Quaternary activity of another NE–SW trending Hsincheng Fault.     

Transport and sediment–water partitioning of trace metals in acid mine drainage: an example from the abandoned Kwangyang Au–Ag mine area, South Korea

Transport and sediment–water partitioning of trace metals (Cr, Co, Fe, Pb, Cu, Ni, Zn, Cd) in acid mine drainage were studied in two creeks in the Kwangyang Au–Ag mine area, southern part of Korea. Chemical analysis of stream waters and the weak acid (0.1 N HCl) extraction, strong acid (HF–HNO₃–HClO₄) extraction, and sequential extraction of stream sediments were performed. Heavy metal pollution of sediments was higher in Chonam-ri creek than in Sagok-ri creek, because there is a larger source of base metal sulfides in the ores and waste dump upstream of Chonam-ri creek. The sediment–water distribution coefficients (K _d) for metals in both creeks were dependent on the water pH and decreased in the order Pb ≈ Al > Cu > Mn > Zn > Co > Ni ≈ Cd. K _d values for Al, Cu and Zn were very sensitive to changes in pH. The results of sequential extraction indicated that among non-residual fractions, Fe–Mn oxides are most important for retaining trace metals in the sediments. Therefore, the precipitation of Fe(–Mn) oxides due to pH increase in downstream sites plays an important role in regulating the concentrations of dissolved trace metals in both creeks. For Al, Co, Cu, Mn, Pb and Zn, the metal concentrations determined by 0.1 N HCl extraction (Korean Standard Method for Soil Pollution) were almost identical to the cumulative concentrations determined for the first three weakly-bound fractions (exchangeable + bound to carbonates + bound to Fe–Mn oxides) in the sequential extraction procedure. This suggests that 0.1 N HCl extraction can be effectively used to assess the environmentally available and/or bioavailable forms of trace metals in natural stream sediments.     

Geochemistry and behavior of REE in stream sediments close to an old Sn-W mine,Ribeira, Northeast Portugal

The abandoned Sn-W Ribeira mine, northeast of Portugal, contained quartz veins with cassiterite, wolframite, scheelite, pyrite, arsenopyrite, sphalerite, chalcopyrite, manganocolumbite, bismuthinite, native bismuth, phosphates and carbonates. The exploration took place on the northern slope of the Viveiros stream, which is an affluent of the Sabor River. The waste-rock dumps and tailings were deposited on the hillside, close to the mine and are nowadays exposed to significant weathering and erosion, as they are not vegetated. The eroded material is transported by the Viveiros stream toward the Sabor River. A seasonal stream drains the tailings. The stream sediments samples were collected along the Viveiros stream, in the seasonal stream, in a seasonal spring at the bottom of the tailings, in the Sabor River and in other streams not affected by mine workings, following the mine influence along the Viveiros stream and in the Sabor River (1.2 km away from the mine workings). The data show that the degree of pollution increases along the Viveiros stream, especially in winter. The highest degree of pollution is for As, In, W, Sn and Bi. The sediments from the drainage of the main tailings are particularly polluted during winter, by Bi, In and Sn. The sedimentary precipitate from the spring is polluted in Cu, As, In, Sn, Ta, W, Bi, Zn, Nb, Ag, Sb and Ta. The sediments from the Sabor River are significantly polluted by As, Ag, In, Sn, W and Bi. The sediments from the regional streams, Viveiros stream and Sabor River have similar REE (NASC normalized) patterns (ΣREE = 131.7–185.9 mg/kg, La_N/Lu_N = 1.23–1.42 and Eu/Eu* = 1.02), while those from the seasonal stream, crossing the main tailings, are enriched in REE (ΣREE = 250.3–283.6 mg/kg, La_N/Lu_N = 1.6–2.09 and Eu/Eu* = 0.96). The general decrease in La_N/Lu_N values with increase in total Fe₂O₃ can be explained by the partitioning of HREE to the solid Fe-oxides phase. The sedimentary precipitate and coatings, which are mainly formed by Fe-oxy-hydroxides, but also contain jarosite, are impoverished in all REE. The impoverishment can be explained by the release of REE from the surface of the Fe-oxy-hydroxides, which occurs due to a local lowering of pH, caused by jarosite dissolution. During successive alternate cycles of wet and dry conditions, takes place the formation of Fe-oxy-hydroxides and jarosite in the sedimentary precipitate and coatings. The subsequent dissolution of jarosite releases acidity, thus promoting de-sorption of REE from the Fe-oxy-hydroxides mineral phases.     

珠江三角洲环境地质控制性因素及问题分析

珠江三角洲经济区地处广东省中南部,濒临南海,海陆相互作用较强烈,新构造运动活跃,侵蚀和剥蚀作用明显,第四系广布,地貌类型多样,是地质环境的过渡带和敏感带,独具特色的区域地质环境必然产生相应的环境地质问题。本文基于现代调查并综合以往研究成果,从地形地貌、新构造运动、海平面变化、第四纪沉积的角度分析了控制珠三角城市群地质环境的重要因素,提出了对可持续城市化进程具有广泛影响的灾害性环境地质问题:地震灾害,软土区地面形变,岩溶塌陷,海岸异常变迁叠加海平面上升等问题。从地质环境的角度分析了这些问题的成因并提出了针对性的对策建议。     

Hydrofracturing in response to the development of an overpressurised subglacial meltwater system during drumlin formation: an example from Anglesey,NW Wales

This paper presents the results of a detailed study of a complex hydrofracture system and host diamictons exposed within a longitudinal section through an elongate drumlin located to the west of Cemlyn Bay, Anglesey, NW Wales. This complex, laterally extensive sand, silt and clay filled hydrofracture system was active over a prolonged period and is thought to have developed beneath the Late Devensian (Weichselian) Irish Sea Ice Stream as it overrode this part of NW Anglesey. The sediment-fill to the hydrofracture system is deformed with kinematic indicators (folds, thrusts, augen) recording a SW-directed sense of shear, consistent with the regional ice flow direction across this part of the island. The lack of any geomorphological evidence for active retreat of the Irish Sea ice across Anglesey has led to the conclusion that hydrofracturing at the Cemlyn Bay site occurred within the bed of the Irish Sea Ice Stream whilst this relatively faster flowing corridor of ice was actively overriding the island. Shear imposed by the overriding ice led to the development of a subglacial shear zone which facilitated the propagation of the hydrofracture system with the laterally extensive feeder sills occurring parallel to Y-type Riedel shears. Although a subglacial setting beneath the active Irish Sea Ice Stream can be argued for the Cemlyn Bay hydrofracture system, its relationship to the formation of the ‘host’ drumlin remains uncertain. However, evidence presented here suggests that hydrofracturing may have occurred during the later stages or post landform development in response to the migration of overpressurised meltwater within the bed of the Irish Sea ice; possibly accompanying the local thinning and shutdown of the Irish Sea Ice Stream on Anglesey.     

朝鲜半岛中南部三叠纪岩浆岩的分布、系列与成因浅析

朝鲜半岛发育大量三叠纪侵入体,主要分布在半岛中部一个北东向走廊地带,该带状区域根据岩性差异,以洪城-高城一线为界分为两个亚带:北亚带(正长岩带/碱性岩带)主要分布在狼林地块南部及京畿地块北部,为碱性系列,以正长岩类为主;南亚带(二长岩带)主要分布在京畿地块南部-岭南地块,多为亚碱性系列,以(纹长)二长岩类为主,部分岩体有闪长岩-辉长岩端元,南部有少量A型花岗岩。这些岩体多形成于ca.230~220Ma,如本文获得的北亚带江北黑云母正长岩228.7±0.8 Ma锆石U-Pb谐和年龄。它们与本区高级变质作用时代接近,分布范围大致对应但稍大,说明它们是同成因的。岩石化学方面,这些岩体均显示高场强元素亏损,轻稀土和大离子亲石元素富集的典型的大陆岩石圈特征。南北亚带相比,北亚带岩体SiO_2和Na_2O等的含量整体上略低,而K_2O、Sr、Ba、La、Eu、Y、Cr等及稀土元素含量略高,轻重稀土分异程度((La/Yb)N)略高。空间上,两个亚带内K_2O/Na_2O和SiO_2有相反的变化趋势:从南向北,两个亚带内K_2O/Na_2O逐渐升高,SiO_2含量逐渐降低;但K_2O+Na_2O和Sr/Y的变化是相似的:南亚带从南向北,北亚带从北向南,两者逐渐降低。我们认为这些岩浆岩为同碰撞或者碰撞后产物,两个亚带之间的界线接近华北和华南古陆缝合带,岩性和成分的空间差异受控于华南古陆(朝鲜半岛南部)向华北古陆(朝鲜半岛北部)之下俯冲所形成的特定壳幔结构。     

鲁中山区新生代沉积盆地古近系含水层富水性分析

正前人研究结果认为,鲁中山区新生代沉积盆地古近系为一套碎屑岩孔隙裂隙含水层,单井涌水量小于100 m~3/d,长期作为弱富水含水层出现,不具有供水意义(康凤新等,2010)。2016年以来,中国地质调查局启动的沂蒙山革命老区1:5万水文地质调查项目,在大汶河流域中上游鲁中山区实施古近系钻孔8眼,涌水量达10800 m~3/d,直接解困人口1.1万。其中在莱芜盆地西北缘实     

Gas-generation potential of shales in small and medium-sized basins: a case study from the Xuanhua Basin,north China

Abstract

Small- and medium-sized basins are widely distributed, and some contain commercial gas reservoirs demonstrating their gas-generation potential. The Xuanhua Basin, which is a small-sized coal-bearing basin in north China, includes a promising target for shale-gas exploration in the Xiahuayuan Formation. In this study, we used this basin as a case study to assess the critical geochemical features for small or medium-sized basins to form commercial gas reservoirs. Total organic carbon (TOC) analysis, Rock-Eval pyrolysis, microscopic observation of macerals, vitrinite reflectance measurement and kerogen stable carbon isotope analysis were performed to characterise the organic geochemistry of the Xiahuayuan shales. The original total organic carbon (TOC_o) content and hydrocarbon-generative potential (S_2o) were reconstructed to further evaluate the gas-generation potential of these shales. In addition, geochemical data of shales from other similar-sized basins with gas discoveries were compared. The results showed that the kerogen from the Xiahuayuan Formation is Type III (gas-prone), and macerals are dominated by vitrinite. TOC values showed a strong heterogeneity in the vertical profiles, with most higher than 1.5?wt%. The measured R_o values ranged from 1.4 to 2.0%. However, thermal maturity was not correlated with the present-day burial depth with higher maturity in the wells closest to the diabase intrusion centre. The remaining generation potential (S₂) averaged 0.91?mg HC/g rock, equal to 1.4?cm³ CH₄/g rock, and the average amount of hydrocarbon generated was 4.33?cm³ CH₄/g rock. In small and medium-sized basins, the TOC content of commercially developed gas shales ranged from 0.5 to 2.5?wt%, organic matter was mainly humic (gas-prone), and the burial depth was generally shallow. Biogenic gas reservoirs for commercial exploitation tend to have larger shale thicknesses (120–800?m) than thermogenic gas reservoirs (60–90?m).

1. The Xiahuayuan Formation is a good gas-source rock with gas-prone kerogen type, relatively high TOC values and moderate thermal maturity.

2. The average amount of hydrocarbon generated from the Xiahuayuan shales is about 4.33?cm³ CH₄/g rock, indicating a potential to form a shale gas reservoir.

3. Owing to the influence of diabase intrusions, the Xiahuayuan shales have entered the dry gas window at relatively shallow-buried depths.

4. Small- and medium-sized basins have the potential to generate commercial gas reservoirs with the generated volume mainly a product of the thickness and maturity of black shales.

     

湖南省九龙山铅锌矿物化探异常综合分析与找矿前景

为进一步摸清九龙山地区区域化探异常与铅锌矿化之间的因果关系、成矿规律和控矿因素,投入1∶1万地质调查、土壤地球化学测量、岩石地球化学测量和激发极化法测量工作,通过综合分析,发现区内4个激电异常区与土壤异常形态相似,平面位置基本重叠吻合,且反映强烈。利用浅表槽探工程在异常中心处揭露到铅锌矿脉,长约760 m,平均厚度为1.40 m,铅平均含量为3.03%,锌平均含量为2.78%,说明九龙山勘查区成矿条件良好,矿产富集,未来深部找矿工作潜力较大。