东昆仑东段东昆中构造带韧性剪切作用及其地质意义

东昆仑东段东昆中构造带经历了多期(次)构造事件,现今保留了复杂多样的构造样式。哈图沟、清水泉—塔妥和沟里等地区构造变形十分强烈,且发育有呈NWW-SEE展布的韧性剪切带。通过野外调研及显微构造研究,对东昆中构造带几何学、运动学及动力学等进行了分析,并通过费氏台和EBSD技术对其进行石英C轴组构分析后认为该剪切带为一压-扭性构造界面,且早期为左旋逆冲,晚期为右旋走滑,变形温度为400~550℃。对剪切带内的石英亚颗粒及动态重结晶粒度测量计算出研究区内韧性剪切带古应力值约为153.791 MPa。哈图沟牦牛山组变形砾岩(4个测点)有限应变测量结果显示,越靠近东昆中断裂带砾石Flinn指数、应变程度、罗德系数(绝对值)越大,且Flinn指数均大于1,属拉伸变形。结合区域地质资料,认为东昆仑东段东昆中韧性剪切带形成于晚海西—印支期。     

ESR DATING OF FLUVIAL SEDIMENTS USING GE CENTER IN QUARTZ

Using the Ge centers of quartz sediments, the buried ages of fluvial sediments were determined by ESR technique. The ESR ages obtained from Ge centers are consistent with the TL ages, correspond with their horizons, accord with the geological background, and every ESR age is available. In this paper, determination of total dose of natural radiation (TD) and the reliability of ESR age using Ge center are also discussed.     

广西金牙金矿床石英的标型特征及其意义

本文通过对金牙金矿床石英的化学成分、包裹体、物理性质及稳定同位素等万面的矿物学特征研究,取得了有价值的成因信息和找矿标志。认为该矿床属浅成中低温地下热(卤)水渗滤型金矿床,成矿物质来源于地层围岩。还指出石英颗粒极细小,多为隐晶至微晶,自形程度低,呈白色或无色、透明;比重低,晶胞棱长a_o大而Co小、单位晶胞体积增大(与标准石英比);红外光谱有1个宽峰、4个吸收峰和2个强的特征峰的波段,具单峰或双峰发热光曲线(在50～350℃范围内);具结构铝,含Ca、Fe、Mn、Au、Ag、Co、Ni、Se、Te与∑REE等杂质元素,其中Au与Al成正相关,而Au与∑REE呈负相关;包裹体呈无色透明、个体细小且少,以液相为主.气液比低,且出现沸腾包体群,其含盐度低,无子矿物,Na、Ca较高,为富含CO_2,CH_4的Ca~(-2)-Na_a-HCO_3~1-Cl型地下热(卤-水(温度305～190℃、压力25669～16945kpa.深度小于1km);δ~(18)O、δ~(18)O_(H_2O)、δD值具大气降水特征,δ~(13)C值类似油田碳等特征,是找“金牙型”金矿的重要找矿标志。     

Towards a climate event stratigraphy for New Zealand over the past 30 000 years (NZ‐INTIMATE project)

It is widely recognised that the acquisition of high‐resolution palaeoclimate records from southern mid‐latitude sites is essential for establishing a coherent picture of inter‐hemispheric climate change and for better understanding of the role of Antarctic climate dynamics in the global climate system. New Zealand is considered to be a sensitive monitor of climate change because it is one of a few sizeable landmasses in the Southern Hemisphere westerly circulation zone, a critical transition zone between subtropical and Antarctic influences. New Zealand has mountainous axial ranges that amplify the climate signals and, consequently, the environmental gradients are highly sensitive to subtle changes in atmospheric and oceanic conditions. Since 1995, INTIMATE has, through a series of international workshops, sought ways to improve procedures for establishing the precise ages of climate events, and to correlate them with high precision, for the last 30 000 calendar years. The NZ‐INTIMATE project commenced in late 2003, and has involved virtually the entire New Zealand palaeoclimate community. Its aim is to develop an event stratigraphy for the New Zealand region over the past 30 000 years, and to reconcile these events against the established climatostratigraphy of the last glacial cycle which has largely been developed from Northern Hemisphere records (e.g. Last Glacial Maximum (LGM), Termination I, Younger Dryas). An initial outcome of NZ‐INTIMATE has been the identification of a series of well‐dated, high‐resolution onshore and offshore proxy records from a variety of latitudes and elevations on a common calendar timescale from 30 000 cal. yr BP to the present day. High‐resolution records for the last glacial coldest period (LGCP) (including the LGM sensu stricto) and last glacial–interglacial transition (LGIT) from Auckland maars, Kaipo and Otamangakau wetlands on eastern and central North Island, marine core MD97‐2121 east of southern North Island, speleothems on northwest South Island, Okarito wetland on southwestern South Island, are presented. Discontinuous (fragmentary) records comprising compilations of glacial sequences, fluvial sequences, loess accumulation, and aeolian quartz accumulation in an andesitic terrain are described. Comparisons with ice‐core records from Antarctica (EPICA Dome C) and Greenland (GISP2) are discussed. A major advantage immediately evident from these records apart from the speleothem record, is that they are linked precisely by one or more tephra layers. Based on these New Zealand terrestrial and marine records, a reasonably coherent, regionally applicable, sequence of climatically linked stratigraphic events over the past 30 000 cal. yr is emerging. Three major climate events are recognised: (1) LGCP beginning at ca. 28 000 cal. yr BP, ending at Termination I, ca. 18 000 cal. yr BP, and including a warmer and more variable phase between ca. 27 000 and 21 000 cal. yr BP, (2) LGIT between ca. 18 000 and 11 600 cal. yr BP, including a Lateglacial warm period from ca. 14 800 to 13 500 cal. yr BP and a Lateglacial climate reversal between ca. 13 500 and 11 600 cal. yr BP, and (3) Holocene interglacial conditions, with two phases of greatest warmth between ca. 11 600 and 10 800 cal. yr BP and from ca. 6 800 to 6 500 cal. yr BP. Some key boundaries coincide with volcanic tephras. Copyright © 2007 John Wiley & Sons, Ltd.     

江西德兴斑岩铜矿石英闪长玢岩成因及成矿学意义

为探究石英闪长玢岩成因及幔源基性岩浆对斑岩铜矿的贡献,本文选取德兴矿床石英闪长玢岩开展了锆石U-Pb定年、Hf同位素和全岩地球化学研究。获得石英闪长玢岩LA-ICP-MS锆石U-Pb年龄为169 Ma,与成矿花岗闪长斑岩侵位时间一致,岩体为中侏罗世岩浆活动的产物。石英闪长玢岩具有低的SiO₂(58.41%~63.12%)和K₂O(1.68%~2.94%)含量及A/CNK值(0.85~1.04),富集大离子亲石元素和轻稀土元素,亏损高场强元素Nb、Ta、Ti和重稀土元素,属于钙碱性到高钾钙碱性系列岩石。具有相对亏损的锆石Hf同位素组成,εHf(t)=2.20~7.93(最大值7.93),指示其源区为岩石圈地幔。锆石稀土元素配分模式图显示出明显的正Ce异常,岩浆氧逸度(lg f_O2)为-20.05~-6.66,达到磁铁矿-赤铁矿氧逸度等级,指示石英闪长玢岩结晶自高氧逸度岩浆。全岩地球化学特征显示,德兴石英闪长玢岩与成矿花岗闪长斑岩及其暗色包体符合岩浆混合的演化趋势,说明成矿花岗闪长斑岩可能是中侏罗世幔源基性岩浆和地壳酸性岩浆大规模混合作用的产物,并且石英闪长玢岩代表了岩浆混合过程中的幔源基性端员。结合前人研究成果,认为在中侏罗世伸展构造背景下,软流圈物质上涌导致新元古代受交代的岩石圈地幔部分熔融形成幔源基性岩浆,基性岩浆的底侵作用诱发下地壳物质熔融并与之发生一定程度的岩浆混合作用,形成了花岗闪长斑岩的母岩浆。高氧逸度幔源岩浆的加入可抑制斑岩体系硫化物的过早饱和,同时为德兴矿床注入了成矿所需的部分挥发分和金属元素。     

估算钙碱性长英质侵入岩结晶压力的地质压力计评述

本文对四种常见的矿物压力计（角闪石全铝压力计、黑云母压力计、榍石压力计和“石英”压力计）的适用性进行了经验性检验。基于国内外典型钙碱性长英质岩体的矿物化学和全岩化学成分数据,采用不同压力计估算岩体侵位压力,并与角闪石全铝压力计结果对比。结果表明：角闪石六次配位Al压力计与广泛使用的角闪石全铝压力计的估算值存在系统相关性;榍石压力计计算的压力与角闪石全铝压力计的估计结果相关性较为显著;基于Qtz—Ab—Or简并花岗岩体系的“石英”压力计可以用于估计准铝质—弱过铝质钙碱性（狭义）花岗岩的结晶压力。但是,经验性的黑云母压力计和基于实验数据的黑云母压力压计均不能很好地复现角闪石全铝压力计的结果。黑云母压力计不适用于估算钙碱性侵入岩的结晶压力。     

河北金厂峪金矿床辉钼矿与金矿化关系研究及意义

辉钼矿Re-Os测年方法现已广泛应用于各类金属硫化物矿床成矿年代学研究领域, 已成为石英脉型金矿床实现直接、准确定年的重要手段。然而, 正确理解辉钼矿与金成矿作用之间的确切关系, 选取具有代表性的辉钼矿样品是测年的前提。本文聚焦冀东地区规模最大的金矿床——金厂峪金矿床, 对其石英-钠长石-多金属硫化物脉中的黄铁矿和辉钼矿两者的产出状态及原位微量元素特征进行了详尽的对比, 研究探讨了金厂峪金矿床中辉钼矿与金矿化之间的关系。研究发现石英-钠长石-多金属硫化物脉含金丰富, 可见金和不可见金均大量赋存, 黄铁矿和辉钼矿均为重要的载金硫化物。镜下矿相学及原位微量元素证据表明, 早期形成的含金黄铁矿经历了再活化过程, 为稍晚形成的富金辉钼矿提供了大量的Au源, 两者可能为同一大的金成矿事件下不同成矿流体脉冲事件的产物。辉钼矿形成于金厂峪金矿的主成矿阶段, 与Au的二次浓集紧密相关, 并可作为高品位金矿体的标志性矿物之一。本文认为在准确厘定辉钼矿与金矿化关系的基础上, 辉钼矿Re-Os方法是一种可靠的石英脉型金矿直接定年手段。     

The Role of Seal and Source Rocks in Fluid-rock Interactions and their Reservoir Effects within the Carbonate Deep Burial Realm

Discoveries of deep high-quality carbonate reservoirs challenged the general understanding on the evolution of porosity decreasing with depth. New mechanisms of pore generation and preservation in the deep realm require to be proposed. Dolostones in the Feixianguan and Dengying Formations experienced maximum depths in excess of 8000 m, but still retained high porosity. Petrographic observation and homogenization temperatures help to identify products of deep fluid-rock interactions, visual and experimental porosity were used to quantify reservoir effects, the distribution of products finally being plotted to unravel the mechanisms. Th data reveal that thermochemical sulfate reduction (TSR), burial dissolution and quartz cementation are typical deep fluid-rock interactions. The SO42? of residual porewater sourced from the evaporative dolomitizing fluid was supplied for TSR in the hydrocarbon column, the TSR-inducing calcite cements were homogeneously dispersed in the hydrocarbon column. Quartz cementation was caused by the increasing acidity and Si-rich residual porewater in the oil column. Burial dissolution is forced by organic acid and limited in oil–water contact. This study suggests that seal and source rocks not only play important roles in hydrocarbon accumulation, but also have a general control on the deep fluid-rock interactions and porosity evolution in the deep burial realm.     

鄂东南付家山脉石英矿杂质特征及其用作高纯石英原料的潜力

作为战略性矿产资源之一,高纯石英已广泛应用于集成电路、半导体芯片、太阳能等高新技术产业中,但是能够生产高纯石英的原料矿床极为稀缺,我国尤为紧缺高纯石英原料矿。鄂东南地区是湖北省脉石英矿床的主要分布区。本文针对鄂东南付家山脉石英矿床,通过光学显微镜、扫描电子显微镜观察了脉石英的脉石矿物类型和包裹体特征,采用电感耦合等离子发射光谱法(ICP-OES)对原矿进行了微量元素分析,旨在获得付家山脉石英矿床的杂质元素特征,进而评价矿床用作高纯石英原料的潜力。结果表明,付家山脉石英矿石SiO₂含量大于99.95%,杂质元素主要为Al、K、Fe、Ti、Ca等,脉石矿物主要有白云母、钾长石、铁氧化物等,流体包裹体较为发育。杂质元素分析结果表明,付家山脉石英原矿质量达到低端高纯石英标准,经传统工艺提纯后,可能具有生产中高端高纯石英的潜力。     

UHT metamorphism on Seram,eastern Indonesia: reaction microstructures and P–T evolution of spinel‐bearing garnet–sillimanite granulites from the Kobipoto Complex

The island of Seram, part of the northern limb of the Banda Arc in eastern Indonesia, exposes an extensive Mio‐Pliocene granulite facies migmatite complex (the Kobipoto Complex) comprising voluminous leucosome‐rich diatexites and scarcer Al–Fe‐rich residual granulites. The migmatites are intimately associated with ultramafic rocks of predominantly lherzolitic composition that were exhumed by substantial lithospheric extension beneath low‐angle detachment faults; heat supplied by the lherzolites was evidently a major driver for the granulite facies metamorphism and accompanying anatexis. Residual garnet–sillimanite granulites sampled from the Kobipoto Mountains, central Seram, contain scarce garnet‐hosted inclusions of hercynite spinel (~1.5 wt% ZnO) + quartz (± ilmenite) in direct grain‐boundary contact – an assemblage potentially indicative of metamorphism under ultrahigh‐temperature (UHT) conditions. thermocalc ‘Average P–T’ reactions and melanosome‐specific thermocalc , T–M_O, and P–T pseudosections in the Na₂O–CaO–K₂O–FeO–MgO–Al₂O₃–SiO₂–H₂O–TiO₂–Fe₂O₃ (NCKFMASHTO) chemical system, supported by Ti‐in‐garnet thermobarometry, are permissive of the rock having experienced a clockwise P–T path peaking at 925 °C and 9 kbar – thus narrowly reaching UHT conditions – before undergoing near‐isothermal decompression to ~750 °C and ~4 kbar. Spinel + quartz assemblages are interpreted to have formed at or just after the metamorphic peak from localized reactions between sillimanite, ilmenite and surrounding garnet. Further decompression of the rock resulted in the formation of complex reaction microstructures comprising cordierite ± plagioclase coronae around garnet, and symplectic intergrowths of cordierite + spinel + ilmenite around sillimanite. Small grains of sapphirine + corundum developed subsequently within spinel by localized quartz‐absent reactions. The post‐peak evolution of the granulites may be related to previously published U–Pb zircon and ⁴⁰Ar/³⁹Ar ages of c. 16 Ma, further substantiating the claim for the Kobipoto Complex granulites having recorded Earth's youngest‐identified episode of UHT metamorphism, albeit at slightly lower temperature and higher pressure than previously inferred. The Kobipoto Complex granulites demonstrate how UHT conditions may be achieved in the ‘modern’ Earth by extreme lithospheric extension, which, in this instance, was driven by slab rollback of the Banda Arc.