木质素的生物降解及其对陆源有机碳指示作用的影响

海洋沉积物中的木质素是陆源有机碳输入的良好标志物,但在迁移埋藏的过程中会发生生物降解,对其指示作用产生影响。本文简要介绍了木质素的结构、指示参数、降解木质素的微生物和降解机理,重点介绍了生物降解过程中木质素参数的变化及对其指示作用的影响,并总结了解决这一问题的方法,指出必须采用多种方法的结合,获取更多的信息才能保证结果的正确性。     

Geochemistry, Nd Isotopic Characteristics of Metamorphic Complexes in Northern Hebei： Implications for Crustal Accretion

The middle segment of the northern margin of the North China Craton （NCC） consists mainly of metamorphosed Archean Dantazi Complex, Paleoproterozoic Hongqiyingzi Complex and unmetamorphosed gabbro-anorthosite-meta-alkaline granite, as well as metamorphosed Late Paleozoic mafic to granitoid rocks in the Damiao-Changshaoying area. The -2.49 Ga Dantazi Complex comprises dioritic-trondhjemitic-granodoritic-monzogranitic gneisses metamorphosed in amphibolite to granulite facies. Petrochemical characteristics reveal that most of the rocks belong to a medium- to high-potassium calc-alkaline series, and display Mg^# less than 40, right-declined REE patterns with no to obviously positive Eu anomalies, evidently negative Th, Nb, Ta and Ti anomalies in primitive mantlenormalized spider diagrams, εNd（t）=＋0.65 to -0.03, and depleted mantle model ages TDM=2.78-2.71 Ga. Study in petrogenesis indicates that the rocks were formed from magmatic mixing between mafic magma from the depleted mantle and granitoid magma from partial melting of recycled crustal mafic rocks in a continental margin setting. The 2.44-2.41 Ga Hongqiyingzi Complex is dominated by metamorphic mafic-granodioritic-monzogranitic gneisses, displaying similar petrochemical features to the Dantazi Complex, namely medium to high potassium calc-alkaline series, and the mafic rocks show evident change in LILEs, negative Th, Nb, Ta, Zr anomalies and positive P anomalies. And the other granitiod samples also exhibit negative Th, Nb, Ta, P and Ti anomalies. All rocks in the Hongqiyingzi Complex show right-declined REE patterns without Eu anomaly. The metamorphic mafic rocks with εNd（t） = -1.64 may not be an identical magmatic evolution series with granitoids that have εNd（t） values of ＋3.19 to ＋1.94 and TDM ages of 2.55-2.52 Ga. These granitic rocks originated from hybrid between mafic magma from the depleted mantle and magma from partial melting of juvenile crustal mafic rocks in an island arc setting. All the -311 Ma Late Paleozoic metamorphic mafic rocks and related granitic rocks show a medium-potassium calc-alkaline magmatic evolution series, characterized by high Mg^#, obviously negative Th, Nb, Ta anomalies and positive Sr anomalies, from no to strongly negative Ti anomalies and flat REE patterns with εNd（t） = ＋8.42, implying that the maflc magma was derived from the depleted mantle. However the other granitic rocks are characterized by right-declined REE patterns with no to evidently positive Eu anomalies, significantly low εNd（t） = -13.37 to -14.04, and TDM=1.97-1.96 Ga, revealing that the granitoid magma was derived from hybrid between maflc magma that came from -311 Ma depleted mantle and granitoid magma from Archean to Early Paleoproterozoic ancient crustal recycling. The geochemistry and Nd isotopic characteristics as well as the above geological and geochronological results indicate that the middle segment of the northern margin of the NCC mainly experienced four crustal growth episodes from Archean to Late Paleozoic, which were dominated by three continental marginal arc accretions （-2.49, -2.44 and 311 Ma）, except the 1.76-1.68 Ga episode related to post-collisional extension, revealing that the crustal accretion of this segment was chiefly generated from arc accretion and amalgamation to the NCC continental block.     

吉林四方甸子钼矿床成岩成矿时代及岩石地球化学特征

吉林四方甸子钼矿床是一新发现的石英脉型钼矿床,矿床产于二长花岗岩中。矿床成矿包括无矿石英脉阶段、石英-辉钼矿-黄铁矿阶段和石英-碳酸盐化阶段。通过对矿区内花岗质岩石进行LA-ICP-MS同位素测年,获得花岗闪长岩成岩年龄为（170.0±1.0） Ma,二长花岗岩成岩年龄为（179.0±1.0） Ma。对含矿石英脉中辉钼矿Re-Os同位素测年分析,获得辉钼矿模式年龄值为（175.0 ± 2.6）～（176.5 ± 2.6）  Ma,加权平均值为（176.1 ± 1.1） Ma,等时线年龄为（176.6 ± 4.2）  Ma,表明四方甸子钼矿床形成于早侏罗世晚期。岩体w(SiO₂)为66.17%～76.60%,w(Na₂O)和w(K₂O)分别为3.15%～5.40%和2.42%～5.42%,里特曼指数σ为2.17～2.93。稀土元素分布形式呈右倾型,轻、重稀土元素分馏明显。微量元素总体显示相对富集Rb、Ba、Th、U等大离子亲石元素（LILE）,亏损Nb、Ta、Ti、P等高场强元素（HFSE）。综合分析表明,岩石为弱过铝质I型花岗岩。成岩成矿动力学背景为燕山早期古太平洋板块向欧亚大陆俯冲作用的大陆边缘环境。     

东天山-北山Cu- Ni- Au- Pb- Zn成矿带主要成矿地质特征及潜力分析

文章通过潜力评价成果汇总和综合分析,结合找矿新理论和该区找矿新进展,重新划定(修定)了东天山-北山Cu-Ni-Au-Pb-Zn重点成矿带的边界。东天山-北山Cu-Ni-Au-Pb-Zn重点成矿带位于西伯利亚板块和塔里木板块之间,在漫长的地质构造演化过程中经历了多次裂解、拼合、造山等构造运动,相应地发生过多期、多阶段的成矿作用,致使此带形成了众多不同矿种、不同类型的矿床,是矿产勘查突破的有利区带。作者从研究区构造演化历史出发,分析了该带区域成矿地质背景,结合带内最新的找矿进展,修订了东天山-北山Cu-Ni-Au-Pb-Zn重点成矿带的成矿谱系,深化了对本成矿带的成矿规律认识;新一轮矿产资源潜力评价证实,带内仍然具有极大的资源潜力,在此基础上,在本带划分了19个远景区,其中9个为重点远景区,10个为一般远景区;提出了带内可能发现新矿床类型(如:砂岩型铀矿、斑岩型金矿等)和新矿种(如稀有稀散金属等);建议本带下一步勘查部署的主攻矿种为Ni、Cu、Mo、Au、W,兼顾Pb、Zn、Ag、Fe和Mn;建议本带主攻类型为基性-超基性岩型镍铜矿、斑岩型铜(钼、金)矿、破碎蚀变岩型金矿、碳酸盐岩-细碎屑岩型铅锌银多金属矿、海相火山岩型铁矿、矽卡岩型银矿以及沉积型锰矿等。该项工作对指导本成矿带下一步矿产勘查部署工作有一定指导意义。     

班公湖-怒江Cu- Au- Fe- Li多金属成矿带主要地质成矿特征及潜力分析

随着地质大调查的开展和班公湖-怒江地区新的找矿进展和预测成果不断涌现,班公湖-怒江作为我国找矿的重点成矿区带之一,故对其开展系统的成矿区划和部署研究工作具有重要意义。本文以最新的研究成果和找矿突破为基础,通过综合分析,在该地区划分新的重要成矿部署区带,厘定边界并将其命名为"班公湖-怒江Cu-Au-Fe-Li多金属成矿带"。结合区域成矿地质背景的综合研究,在区内划分了3个Ⅲ级成矿带,初步建立了班公湖-怒江Cu-Au-Fe-Li多金属成矿带成矿谱系,其成矿作用具有多期次发育的特点,其中喜山期与燕山期是该矿带的主要成矿期。研究区主要成矿类型为斑岩型铜金矿、矽卡岩型铜金矿、变质碎屑岩中脉型岩金矿、矽卡岩型铁矿、现代盐湖型钾盐、硼矿、锂矿等。结合区域找矿进展和潜力评价最新成果,认为本区Cu、Au、Fe、Li、K、B找矿潜力巨大,为下一步勘查部署的主攻矿种,同时在本区划分了3个远景区,其中2个为重点远景区,1个为一般远景区,对研究区下一步矿产勘查部署工作有一定指导意义。     

Surface Rupture and Co-seismic Displacement Produced by the Ms 8.0 Wenchuan Earthquake of May 12th, 2008, Sichuan, China: Eastwards Growth of the Qinghai-Tibet Plateau

An earthquake of Ms 8 struck Wenchuan County, western Sichuan, China, on May 12^th, 2008 and resulted in long surface ruptures （〉300 km）. The first-hand observations about the surface ruptures produced by the earthquake in the worst-hit areas of Yingxiu, Beichuan and Qingchuan, ascertained that the causative structure of the earthquake was in the central fault zones of the Longmenshan tectonic belt. Average co-seismic vertical displacements along the individual fault of the Yingxiu-Beiehuan rupture zone reach 2.514 m and the cumulative vertical displacements across the central and frontal Longmenshan fault belt is about 5-6 m. The surface rupture strength was reduced from north of Beichuan to Qingchuan County and shows 2-3 m dextral strike-slip component. The Wenchuan thrust-faulting earthquake is a manifestation of eastward growth of the Tibetan Plateau under the action of continuous convergence of the Indian and Eurasian continents.     

New Research Results on Mechanism, Surface Rupture, Deep Controlling Factors and Stress Measurements of the Wenchuan Earthquake—Earth Scientists’ Post-quake Actions

Abstract: On May 12th, 2008, the Mw7.9 Wenchuan earthquake ruptured the Beichuan, Pengguan and Xiaoyudong faults simultaneously along the middle segment of the Longmenshan thrust belt at the eastern margin of the Tibetan plateau. Field investigations constrain the surface rupture pattern, length and offsets related to the Wenchuan earthquake. The Beichuan fault has a NE-trending right-lateral reverse rupture with a total length of 240 km. Reassessment yields a maximum vertical offset of 6.5±0.5 m and a maximum right-lateral offset of 4.9±0.5 m for its northern segment, which are the largest offsets found; the maximum vertical offset is 6.2±0.5 m for its southern segment. The Pengguan fault has a NE-trending pure reverse rupture about 72 km long with a maximum vertical offset of about 3.5 m. The Xiaoyudong fault has a NW-striking left-lateral reverse rupture about 7 km long between the Beichuan and Pengguan faults, with a maximum vertical offset of 3.4 m and left-lateral offset of 3.5 m. This pattern of multiple co-seismic surface ruptures is among the most complicated of recent great earthquakes and presents a much larger danger than if they ruptured individually. The rupture length is the longest for reverse faulting events ever reported.     

贵州织金洞世界地质公园喀斯特成景机制及模式研究

本文将织金喀斯特分为8大类:洞穴、峡谷、天生桥、天坑、高峰丛、丘陵、单面山与象形山、水文遗迹等,它们以下三叠统海相碳酸盐岩为物质基础,有序、集中分布于织金洞、绮结河、东风湖三片相对独立,却又以绮结河为纽带紧密相连的喀斯特区域内,共同构成一个以洞穴、峡谷、天生桥、天坑为核心,形态雄伟、典型、优美、珍稀的高原喀斯特景观群。同时在对公园区域成景背景进行分析和研究的基础上,认为织金喀斯特的形成演化,始于古近纪,以三处喀斯特区域相互之间水力联系的演变为主轴,历经四个阶段:初始阶段(古近纪期间,喀斯特地层出露)→雏形阶段(分轴型离散岛屿式成景过程)→重要发育阶段(主轴型离散岛屿式与集合型岛屿式成景过程)→现代喀斯特阶段。期间,三个喀斯特区域产生不同的喀斯特响应过程:(1)织金洞区域,以织金洞地下河的演变为主轴,历经横向裂隙式岩溶水→地下河道→抬升形成化石洞穴/洞穴景观发育阶段/袭夺地表河(古新寨河)→地下河大规模发育→抬升形成化石洞穴/被袭夺阶段/→地下河小规模发育/洞穴景观发育等不同的地下岩溶循环发育阶段,形成了规模宏大的4层迷宫式化石洞穴系统—织金洞洞穴系统,洞内次生化学沉积物类型齐全,形态优美、独特,体量巨大,现代总体属于已停止发育的化石型洞穴喀斯特区域。(2)绮结河区域,以绮结河的演变为主轴,历经地表流水各向分散流动阶段→地表河阶段→地下河阶段→地下河改道/袭夺阶段→地下河大规模发育阶段→改道/明流与伏流交替阶段等不同的地表与地下岩溶交替循环发育阶段,峰丛、洞穴、峡谷、天坑、天生桥等地貌有序分布于河谷上或其两侧,协同共生,现代总体属于地表与地下喀斯特正在相互交替发育的区域。(3)东风湖区域,以六冲河的演变为主轴,历经持续、漫长、大规模、高强度的横向—纵向侵蚀、切割,峰丛、丘陵、象形山、单面山、峡谷有序分布于其上宽下窄的河谷上或其两侧,共生发育,现代总体属于正在发育的地表喀斯特区域。(4)整个公园,以三处喀斯特区域相互之间水力联系的演变为主轴,历经四个不同的喀斯特阶段,及各区域不同的喀斯特响应过程,形成独特的织金高原喀斯特景观群,现代总体上正在分区进行着三种不同的喀斯特过程。在上述分析的基础上,提出分轴型、主轴型、离散型和集合型等四种岛屿式成景机制。同时,通过与相似、典型岩溶区域(如广西乐业、重庆武隆等)的成景模式进行对比,将织金喀斯特成景模式归纳为"相邻岛屿式成景模式"。     

TTG片麻岩与地壳早期动力学

英云闪长质－奥长花岗质－花岗闪长质片麻岩（ＴＴＧ）在太古宙高级区和绿岩－花岗岩区广泛分布。大量研究表明它们主要是由与玄武岩成分相当的各类源岩在不同条件下部分熔融形成的，也有一些由玄式质岩浆分离结晶或未成熟杂砂岩部分熔融形成。高温高压实验证明，玄武质岩石在中低压水饱和条件下熔融产生钙碱性岩浆，在中、高压、ｐｆ＜Ｐｔ条件下熔融程度在１０％～３０％时产生英云闪长质－奥长花岗质岩浆。不同压力下熔融残留相成分和比例有明显差异，导致ＲＥＥ配分模式的不同。只有在１．６ＧＰａ左右或更高压力、ｐｆ＜ｐｔ条件下才产生与太古宙ＴＴＧ杂岩地球化学性质相同或相似的熔体。因此，对ＴＴＧ片麻岩的地球化学性质、成因和生成环境的研究对探讨地壳早期的动力学过程具有重要意义。     

Geochemical Characteristics and Sources of Ore-forming Fluids of the Mayuan Pb-Zn Deposit, Nanzheng, Shaanxi, China

The Mayuan stratabound Pb-Zn deposit in Nanzheng,Shaanxi Province,is located in the northern margin of the Yangtze Plate,in the southern margin of the Beiba Arch.The orebodies are stratiform and hosted in breciated dolostone of the Sinian Dengying Formation.The ore minerals are primarily sphalerite and galena,and the gangue minerals comprise of dolomite,quartz,barite,calcite and solid bitumen.Fluid inclusions from ore-stage quartz and calcite have homogenization tempreatures from 98 to 337℃ and salinities from 7.7 wt%to 22.2 wt%(NaCl equiv.).The vapor phase of the inclusions is mainly composed of CH_4 with minor CO_2 and H_2S.The δD_(fluid) values of fluid inclusions in quartz and calcite display a range from-68‰ to-113‰(SMOW),and the δ~(18)O_(fluid)values calculated from δ~(18)O_(quartz) and δ~(18)O_(calcite) values range from 4.5‰ to 16.7‰(SMOW).These data suggest that the ore-forming fluids may have been derived from evaporitic sea water that had reacted with organic matter.The δ~(13)C_(CH4) values of CH_4 in fluid inclusions range from-37.2‰ to-21.0‰(PDB),suggesting that the CH_4 in the ore-forming fluids was mainly derived from organic matter.This,together with the abundance of solid bitumen in the ores,suggest that organic matter played an important role in mineralization,and that the thermochemical sulfate reduction(TSR) was the main mechanism of sulfide precipitation.The Mayuan Pb-Zn deposit is a carbonate-hosted epigenetic deposit that may be classified as a Mississippi Valley type(MVT) deposit.