Geology,ore facies and sulphur isotopes of the Koushk vent-proximal sedimentary-exhalative deposit,Posht-e-Badam Block,Central Iran

The Koushk zinc–lead deposit in the central part of the Zarigan–Chahmir basin, central Iran, is the largest of several sedimentary–exhalative (SEDEX) deposits in this basin, including the Chahmir, Zarigan, and Darreh-Dehu deposits. The host-rock sequence consists of carbonaceous, fine-grained black siltstone with interlayered rhyolitic tuffs. It corresponds to the upper part of the Lower Cambrian volcano-sedimentary sequence that was deposited on the Posht-e-Badam Block due to back-arc rifting of the continental margin of the Central Iranian Microcontinent. This block includes the late Neoproterozoic metamorphic basement of the Iran plate, overlain by rocks dating from the Early Cambrian to the Mesozoic. Based on ore body structure, mineralogy, and ore fabric, we recognize four different ore facies in the Koushk deposit: (1) a stockwork/feeder zone, consisting of a discordant mineralization of sulphides forming a stockwork of sulphide-bearing dolomite (quartz) veins cutting the footwall sedimentary rocks; (2) a massive ore/vent complex, consisting of massive replacement pyrite, galena, and sphalerite with minor arsenopyrite and chalcopyrite; (3) bedded ore, with laminated to disseminated pyrite, sphalerite, and galena; and (4) a distal facies, with minor disseminated and laminated pyrite, banded cherts, and disseminated barite. Carbonatization and sericitization are the main wall-rock alterations; alteration intensity increases towards the feeder zone. The δ³⁴S composition of pyrite, sphalerite, and galena ranges from?+6.5 to?+36.7‰. The highest δ³⁴S values correspond to bedded ore (+23.8 to?+36.7‰) and the lowest to massive ore (+6.5 to?+?17.8‰). The overall range of δ³⁴S is remarkably higher than typical magmatic values, suggesting that sulphides formed from the reduction of seawater sulphate by bacteriogenic sulphate reduction in a closed or semi-closed system in the bedded ore, whereas thermochemical sulphate reduction likely played an important role in the feeder zone. Sulphur isotopes, along with sedimentological, textural, mineralogical, and geochemical evidences, suggest that this deposit should be classified as a vent-proximal SEDEX ore deposit.     

华熊地块中生代岩浆作用的物质继承性

中生代是华熊地块最重要的岩浆作用时期。通过对其中主要地体中燕山期改造型花岗岩和同熔型花岗岩的同位素研究,结合其形成物质背景和地质特征,认为它们的物质特征主要取决于它们继承各自不同的地体物质(特别是基底物质)和同一地体物质的多少程度。地体及其中生代岩浆作用的构造环境是解释这一继承机理的主要因素。     

Convergence History of the Songliao and Jiamusi Blocks in the Eastern End of Central Asian Orogenic Belt: Evidence from Detrital Zircons of Late Paleozoic Sedimentary Rocks

Central Asian Orogenic Belt(CAOB) is one of the largest accretionary orogenic belts in the world. The eastern segment of CAOB is dominated by Paleozoic Paleo Asian Ocean tectonic regime, Mesozoic Paleo-Pacific tectonic regime and Mongolian-Okhotsk tectonic regime. The Songliao and Jiamusi blocks are located in the easternmost part of the CAOB and are the key region to solve the problem about overprinting processes of multiple tectonic regimes. It is generally believed that the Mudanjiang Ocean between the two blocks was finally closed in the Mesozoic, but the Paleozoic magmatism also developed along the Mudanjiang suture zone, while on both sides of the suture zone, there were comparable Paleozoic strata, indicating that the two blocks had converged during the Paleozoic, and the evolution history of the two blocks in the Late Paleozoic remains controversial. The Carboniferous-Permian terrestrial strata mainly developed in Binxian, Wuchang and Tieli on Songliao Block, Baoqing and Mishan on Jiamusi Block. Samples from the Songliao and Jiamusi blocks in the Late Carboniferous-Early Permian and Late Permian are collected for comparative analysis. The LAICP-MS zircon U-Pb dating results show that the maximum depositional age of Middle Permian Tumenling Formation and Late Permian Hongshan Formation in Songliao Block is ～260 Ma, while that of Tatouhe Formation and Carboniferous strata in Jiamusi Block are ～290 Ma and ～300 Ma, respectively, which supports the previous stratigraphic division scheme. The age peaks of ～290–300 Ma, ～400 Ma, ～500 Ma appeared in the Late Carboniferous to Early Permian strata of Jiamusi Block and the Middle Permian strata of Songliao Block. The age peak of ～500 Ma in the Middle Permian strata of Songliao Block may come from the Cambrian basement, Mashan Complex, of Jiamusi Block, while the age peaks of ～420–440 Ma in the Carboniferous strata of Jiamusi Block may come from the Silurian magmatic arc in Zhangguangcai Range in the eastern margin of Songliao Block, reflects the history that they had been potential sources of each other, indicating that they may have combined in the Paleozoic. The Hongshan Formation of Songliao Block in the Late Permian lacks the age peak of ～500 Ma, which indicate that Jiamusi Block was not the provenance of Songliao Block in the Late Permian, that is, there was a palaeogeographic isolation between the two blocks. Combined with the ～210 Ma bimodal volcanic rocks developed along the Mudanjiang suture zone reported previously, we believe that the oceanic basin between the Songliao and Jiamusi blocks should have been connected in Late Permian and reopened during Late Permian to Late Triassic.     

湘东北文家市蛇绿混杂岩带的发现及意义

在湘东北文家市首次识别出蛇绿岩套残片 ,它由变沉积岩、变玄武岩、变辉绿岩、变辉长岩、变辉石岩类及变硅质岩组成。综合其地质学、岩石学、地球化学和同位素年代学的资料 ,提出文家市蛇绿岩可能形成于有限小洋盆的构造环境。文家市蛇绿混杂岩带、前陆盆地、磨拉石建造和“S”型花岗岩等构造岩石组合记录了碰撞造山的全过程 ,证实了江南雪峰古陆属元古宙造山带。这一发现为华南前寒武纪的大地构造格架和地壳演化提供了依据 ,同时该地区也将成为研究早期华南大陆地壳演化———武陵运动的关键地带。     

近45年拉萨深层地温变化趋势分析

利用1961—2005年拉萨0.8 m, 1.6 m和3.2 m逐月平均地温, 采用气候倾向率、累积距平、信噪比等气候诊断方法, 分析了近45年拉萨深层平均地温的变化趋势, 以及异常、突变等气候特征。结果表明:近45年拉萨0.8 m和1.6 m年平均地温呈极显著的增温趋势, 倾向率为 (0.58~0.69 ℃)/10a;0.8 m和1.6 m平均地温倾向率春季最大, 秋季最小; 3.2 m平均地温却以夏季升幅最大, 冬季最小; 与同时期平均气温的增温幅度比较, 地温增幅更大; 20世纪60—90年代0.8 m和1.6 m年平均地温呈明显的逐年代升高趋势; 季平均地温20世纪60—70年代均偏低, 80年代大部分季节仍略偏低, 90年代都表现为正距平; 0.8 m, 1.6 m和3.2 m年平均地温均在1999年出现了异常偏暖, 异常偏冷现象仅发生在1.6 m土层上, 时间为1963年; 夏季深层平均地温异常偏暖均发生在1999年; 冬季0.8 m和1.6 m平均地温多异常偏冷年份, 主要发生在20世纪60年代; 1999, 2002—2005年冬季3.2 m平均地温异常偏暖; 夏、秋季和年平均地温的气候突变都出现在1986年, 冬、春季发生在1983年。     

拉萨光合有效辐射的变化趋势及其估算方程的建立

利用2005年1月-2010年12月中国生态研究网络拉萨农田站的观测数据,分析了拉萨地区光合有效辐射Qp的变化特征.结果表明,拉萨地区的Qp与太阳总辐射Rs具有相同的月变化和日变化特征,Rs与Qp的平均日累计值分别为20.2 MJ·m-2和37.2 mol·m-2,Qp呈逐年递减趋势.Rs与Qp的月变化表现为6月最大、1月最小,其最大、最小值分别为25.4 MJ·m-2、14.0 M J·m-2和48.7 mol·m-2、25.2 mol·m-2.日变化表现为正午大、早晚小.光合有效辐射系数(Qp/Rs)的变化范围在1.3～3.2 mol·MJ-1之间,年平均值为1.89 mol·MJ-1,呈逐年递减趋势,2010年比2005年降低了6.7％.Qp/Rs的日变化表现为早晚大、正午小,季节变化表现为夏季最大、春秋季次之、冬季最小,而且夏、冬两季的季节变化较为明显,冬季比夏季低10.6％.通过分析Qp与晴空指数和太阳天顶角之间的关系建立了拉萨地区Qp的估算方程,相对误差在4.49％左右.     

苏皖地块构造演化、苏鲁造山带形成及其耦合的盆地发育

郯庐断裂带一度是古特提斯洋域中的转换断层,其东的苏皖地块和胶辽克拉通分别是曾经独立于扬子克拉通和华北克拉通之外的构造单元。苏皖地块原属中朝构造域,因中元古代时苏鲁洋的张开而向南漂移,震旦纪起归入华南构造域。受北东东-近东西向的江南断裂和江绍断裂右行走滑活动控制,苏皖地块及怀玉地块在石炭纪末-三叠纪时脱离华南构造域,成为古特提斯洋域中的中间地块。中国东部地区东亚燕山期山系的形成受两个地球动力学系统制约:一是苏鲁洋的消减及闭合后苏皖地块与胶辽克拉通的碰撞,二是江南断裂和江绍断裂的先剪后压,苏皖地块与拼合了的扬子-华北克拉通间发生斜向会聚和剪切造山,怀玉地块仰冲超叠在苏皖地块上。分5个阶段(印支期消减,早-中侏罗世斜向会聚,晚侏罗-早白垩世消减,早白垩世碰撞和燕山造山带坍塌)叙述了中生代造山作用的表现和特点,探讨了与各阶段造山作用耦合的盆地类型和时空分布。因燕山造山带的坍塌而燕山运动构建的“盆”“山”关系解脱,中国东部第三纪的伸展盆地直接叠加在燕山造山带的坍塌裂谷上。     

粤西云开地块内高州地区深熔混合岩的锆石U-Pb年龄

云开地块区域混合岩是在低压变质作用基础上形成的。多数古成体原岩是富黑云母的过铝质片麻岩。混合岩野外特征、岩石学、矿物空间分布和地球化学综合研究均表明,该区浅色体是深熔成因的。单颗粒锆石定年结果表明,混合岩形成于加里东期,其时代为３９４ ～４４９Ｍａ,这期混合岩化作用可能与云开地块大规模的加里东期岩浆活动有关。     

扬子板块北缘中段多期褶皱构造的变形特征及叠加关系

扬子板块北缘在中生代期间经历多期构造变形,早期形成的构造样式多被后期的构造变形改造破坏,仅在大巴山弧形断裂和大洪山弧形带之间的南漳一带较好地保存了早期的构造变形样式。笔者通过对当阳复向斜北段发育的褶皱构造的构造要素测量统计和褶皱叠加关系的解析,在扬子板块北缘中段南漳一带识别出三期走向不同的褶皱叠加构造,按发育早晚顺序分别为NW-SE走向褶皱、NE-SW走向褶皱和近EW走向褶皱,分别对应扬子板块向北俯冲以及后期转入陆内变形、江南–雪峰褶皱逆冲带向NW逆冲推覆和晚侏罗世到早白垩世期间大巴山向SW推进等构造变形过程。     

大庆宋芳屯油田肇35区块葡萄花油层非均质性研究

从储层宏观与微观非均质性入手,分别研究了肇35区块葡萄花油层的层内、层间、平面和微观非均质性特征及主控因素,研究区层内非均质性主要受到沉积构造、渗透率韵律以及夹层分布等的影响;从物性和隔层分布特征方面分析了层间非均质性特征,自下而上葡萄花油层非均质性呈现弱→强→弱的变化趋势;平面非均质性特征受砂体及沉积微相展布影响较大,沿河道延伸方向非均质性较好。研究区主要发育正常粒间孔、缩小粒间孔和粒内溶蚀孔,整体上储层微观孔隙结构发育良好。从不同方面分析了研究区非均质性对剩余油分布的影响,沉积微相类型和成岩作用是控制储层非均质性的主因素。最终对葡萄花油层主力小层进行储层评价,预测了有利储层的发育面积和分布范围,为下一步的勘探开发提供一定的依据。