GPS单历元阻尼LAMBDA算法在水库形变监测中的应用

形变监测点近似坐标的概略精度指标为GPS单历元定位提供了有利条件,结合水库形变监测点形变特征,采用平滑处理方法,“GPS单历元阻尼LAMBDA算法”可用于静态形变测量．这就将以往的“静态监测模式”与“动态监测模式”统一为“动静态监测模式”。采用模拟实验和清江隔河岩大坝实测数据检验了“动静态模式”的有效性,结果表明：单历元定位精度优于2cm,两小时观测数据的平滑坐标可以达到3mm的定位精度。同时讨论了具有两个基准站的数据处理方法,比较了单基准站与双基准站对监测点定位精度的影响。     

阴洼山断裂全新世活动特征与年代学研究

阴洼山断裂属于河西走廊内的断裂带,位于嘉峪关以西28km的阴洼山北侧及附近,呈NW向延伸,长25km,自NW向SE具有活动时代逐渐变新的特点。其西北段仅切错了白垩系和上新统,中段则切错到上更新统(被断最新坡积物22.4kaBP,覆盖坡积物8.6kaBP),而东南段切错了全新统(断层楔堆积物4.8～5.1kaBP)。断裂的活动性质在剖面上表现为西南盘上升、东北盘下降的相对位移,而平面上为右行的走滑。该断裂在晚更新世末(10～11kaBP左右)和全新世中期(5kaBP左右)发生过2次明显的新活动     

On age of Nazimovskaya and Khasan formations in the Paleogene succession of southwestern Primor’e

Materials of previous studies and new original geological and paleobotanic data are used to substantiate synchronism (late Eocene) of the Khasan and Nazimovskaya formations, the key stratigraphic units of the Paleogene in Primor’e. Coal-bearing sediments of the units rest upon early-middle Eocene volcanics (Kraskino rhyolite tuffs, Zaisanovka basaltic andesites) being overlain by the lower Fatash Subformation of the lower Oligocene with flora of the Kraskino type. The Ust’-Davydovskaya Formation of the Rechnoi Peninsula (outskirts of Vladivostok) is the most probable analogue of the Khasan (=Nazimovskaya) Formation.     

Oligocene–Miocene formation of the Haifa basin: Qishon–Sirhan rifting coeval with the Red Sea–Suez rift system

During mid-Oligocene to early-Miocene times the northeastern Afro-Arabian plate underwent changes, from continental breakup along the Red Sea in the south, to continental collision with Eurasia in the north and formation of the N–S trending Dead Sea fault plate boundary. Concurrent uplift and erosion of the entire Levant area led to an incomplete sedimentary record, obscuring reconstructions of the transition between the two tectonic regimes. New well data, obtained on the continental shelf of the central Levant margin (Qishon Yam 1), revealed a uniquely undisturbed sedimentary sequence which covers this time period. Evaporitic facies found in this well have only one comparable location in the entire eastern Mediterranean area (onland and offshore) over the same time frame — the Red Sea–Suez rift system. Analysis of 4150 km of multi and single-channel seismic profiles, offshore central Levant, shows that the sequence was deposited in a narrow basin, restricted to the continental shelf. This basin (the Haifa Basin) evolved as a half graben along the NW trending Carmel fault, which at present is one of the main branches of the Dead Sea fault. Re-evaluation of geological data onland, in view of the new findings offshore, indicates that the Haifa basin is the northwestern-most of a larger series of basins, comprising a failed rift along the Qishon–Sirhan NW–SE trend. This failed rift evolved spatially parallel to the Red Sea–Suez rift system, and at the same time frame. The Carmel fault would therefore seem to be related to processes occurring several million years earlier than previously thought, before the formation of the Dead Sea fault. The development of a series of basins in conjunction with a young spreading center is a known phenomenon in other regions worldwide; however this is the only known example from across the Arabian plate.     

Reply to Molina-Garza et al. (2019) “Discussion of: Ortega-Flores et al. (2018) provenance analysis of Oligocene sandstone from the Cerro Pelón area,southern Gulf of Mexico”

ABSTRACT

The origin of the Oligocene turbidites from the Cerro Pelón area in south Gulf Mexico proposed by Ortega-Flores et al. (2018) is in disagree with the interpretations made by Molina-Garza et al. (2019), which main criticism is based on U-Pb ages of detrital zircons from the matrix of a conglomerate unit, which they refer to as ‘Nanchital Conglomerate’, as well as on the presence of limestone, gabbros, and mafic protolith-derived clasts. Molina-Garza et al. (2019) basically interpret the Nanchital Conglomerate as Miocene in age, which was sourced mainly from metamorphic complexes including their sedimentary covers located to the west and south of the Cerro Pelón area. For some reason, Molina-Garza et al. (2019) suppose that the Nanchital Conglomerate should have the same provenance sources that the Oligocene turbidites from Cerro Pelón area, reported by Ortega-Flores et al. (2018). Based on the foregoing, we strongly disagree with Molina-Garza et al. (2019) considering that, from the beginning, they intend to compare two units of different age. Additionally, the scarce data reported from both the matrix and the clasts of the Nanchital Conglomerate are not determinant for interpreting the provenance of this conglomeratic unit and subsequently, to consider the same rock sources from the Oligocene through Miocene time.     

东昆仑夏日哈木岩浆铜镍硫化物矿床成矿时代的厘定及其找矿意义

青海省夏日哈木岩浆硫化物矿床是近两年于东昆仑造山带新发现的超大型镍矿床,其赋矿岩性与形成时的地球动力学机制和构造环境认识是制约找矿更大突破的关键控制因素。本文拟通过成岩成矿时代的确定来探讨其形成时的构造背景,进而指出东昆仑地区该类矿床的找矿意义和潜力。野外钻孔岩心详细编录,发现岩浆硫化物绝大多数都富集于橄榄岩相、辉石岩相等的超镁铁质岩类,与矿化较弱的辉长岩非同期的产物。对采集到的矿体顶底板无矿化的橄辉岩钻孔岩心样品挑选锆石进行U-Pb年代学测定,获得了(412.9±1.8)Ma(MSWD=1.2)和(410.9±1.6)Ma(MSWD=3.1)的谐和年龄。同样方法获得的辉长岩的年龄则老20 Ma,进一步说明含矿超镁铁质岩与无矿辉长岩非同期产物。系统的橄榄石成分及Fo值研究,初步揭示了岛弧岩浆特点的信息。综合区域内榴辉岩的厘定及年龄测试,初步认为夏日哈木超大型岩浆铜镍硫化物矿床岩浆源区表现了东昆仑弧的特点,随着部分熔融发生的岩浆上涌,深部和浅部均产生了硫化物的不混溶作用,分异的岩浆于柴达木克拉通南缘东昆仑造山带碰撞后的构造薄弱部位成岩成矿,地壳浅部围岩S的混入对镍矿体的形成具有重要贡献。这一认识对于东昆仑其他镁铁-超镁铁质侵入岩体的含矿性评价和拓展区域找矿潜力具有重要的找矿指示意义和研究价值。     

大别山北麓斑岩型钼矿床地质特征、成矿时代及其成矿构造背景

在野外调查和测试分析的基础上,结合前人的研究成果,综合论述了大别山北麓斑岩型钼矿床的地质特征、形成时代和构造背景。大别山北麓斑岩型钼矿床总体沿区域构造线呈北西向狭长带状展布,具有近东西向成带、南北向成群的空间展布特征,其形成与燕山期中酸性浅成-超浅成小型花岗斑岩体有关,钼矿床直接产于岩体内外接触带及其附近的围岩中,矿床类型主要为斑岩型、斑岩-矽卡岩型及少量热液石英脉型。结合Re-Os同位素年龄数据,探讨了大别山北麓斑岩型钼矿床的成矿物质来源、成矿流体、成矿时代、主要成矿作用的时限以及成矿地球动力学背景。结果表明:大别山北麓地区钼矿床的主要成矿作用时限为142~137 Ma和127~110 Ma,对应的地球动力学背景为中国东部地球动力学体制大转换晚期的岩石圈拆沉及伸展减薄的构造背景。     

华北克拉通北缘西拉沐沦钼多金属成矿带钼矿化类型、特征及地球动力学背景

最近,在华北克拉通北缘,沿东西走向的西拉沐沦构造带两侧异军突起地出现了一个400多千米长、300千米宽的钼矿带,短短4年时间已经发现了10余个大型-中型钼矿床,显示了巨大的资源前景。钼矿床的空间分布受区域东西向、北东向及北西向断裂联合控制,钼矿床的形成与中生代的中酸性侵入体关系密切,矿床产于花岗岩体中、斑岩体内外接触带或附近,矿床类型以斑岩型、石英脉型、火山热液型及云英岩型为主。空间关系表明钼矿床的形成主要与中生代富硅、富钾酸性侵入岩有关。成矿年代学研究表明,西拉沐沦成矿带钼矿具有三期成矿作用：包括245Ma、150Ma和138Ma。其对应的成矿动力学背景为印支期华北板块与西伯利亚板块碰撞造山后伸展阶段和燕山期中国东部构造大转折期。其中,印支期的成矿作用和相应的岩浆活动在以往的工作中较少论及。     

Authigenic dolomites in the Eocene–Oligocene organic carbon-rich shales from the Polish Outer Carpathians: Evidence of past gas production and possible gas hydrate formation in the Silesian basin

Eocene–Oligocene dolomite concretions and beds from the Grybów and Dukla units of the Polish Outer Carpathians were studied. These rocks occur in the organic carbon-rich, marine and fine-grained deposits of hemipelagic or turbiditic origin. Mineralogic, elemental and stable C and O isotopic composition of the dolomites was determined. Results indicate that the rocks were formed by precipitation of predominantly Fe-rich dolomite cement close to the sediment-water interface prior to significant compaction. The main source of bicarbonate for dolomite formation was bacterial methanogenesis as evidenced by the high δ¹³C values up to 16.6‰. The main source of alkalinity was probably weathering of silicate minerals which might have also liberated Ca and Mg ions for the dolomites to form. The distribution of these dolomites indicates that microbial methane production was widespread in the Silesian basin. Moreover, formation of some dolomites in the Eastern part of the Dukla unit was probably associated with gas hydrates as suggested by the elemental and oxygen isotopic composition of dolomitic matrix. Therefore, the dolomites may serve as a proxy of areas where biogenic methane was produced, where the rocks had high hydrocarbon potential, and where hydrates could have existed.Detailed mineralogic and petrographic analyses allowed for the reconstruction of the diagenetic sequence and the evolution of pore fluids. Textural relationships between successive cement generations indicate that the central parts of the composite dolomite crystals experienced corrosion and that the latest ankerite cement filled the secondary intragranular cavities within those crystals. This observation shows that reconstructions of pore fluid evolution based on core-to-rim analyses of such composite crystals may lead to wrong interpretations. Septarian cracks developed in the dolomites are often filled with multistage cements. The earliest generations are ferroan dolomite and ankerite cements which precipitated within the cracks simultaneously to the ferroan dolomite and ankerite cements from the matrix of the dolomitic rocks which shows that septarian cracking occurred very early, during the final stages of concretionary formation. These cements were followed by the late-diagenetic precipitates, mainly quartz, kaolinite and blocky calcite. This calcite is commonly associated with bitumen which shows that it precipitated during or after oil migration in the decarboxylation zone.     

内蒙古中部大青山新地沟绿岩带型金矿的成矿时代

内蒙古新地沟金矿床产于大青山太古宙花岗岩-绿岩带中,受色尔腾山群柳树沟组中基性火山岩系和韧性剪切带控制.容矿岩石主要是变安山质-英安质火山岩类.为解决主矿体的形成时代,采用石英40Ar/39Ar法,直接测定了含金石英细脉浸染状矿石中石英的形成时代,结果表明新地沟金矿的形成时代为1991.43～1988.93Ma.由此提出新地沟金矿的成因主要与吕梁期韧性剪切带中的变质变形作用有关.