Late Paleozoic Mantle Source Nature of Tianshan Orogen, Northwest China: Evidence from the Geochemistry, Zircon U-Pb Dating, Hf and Whole Rock Sr-Nd-Pb Isotopes of the Mafic Dykes

The Tianshan Orogen(TO)is one of the largest typical accretionary orogenic belts in the world.Of which,the late Paleozoic was a critical era to understand the tectonic and geodynamic transition from accretion to collision.However,the late Paleozoic tectonic evolutionary history,especially for the time of the ocean-continent transition,is still debated although the origin and tectonic settings for the Paleozoic volcanic,felsic igneous magmatism in TO and reginal geology have been done in the last decades.In contrast,the researches on the mafic dykes in TO was not systematically carried out till now.Reginal-scale mafic dykes are commonly regarded as the products created in a extensional setting,and used to identify the major tectonic events such as rifting and continental break-up and further trace the mantle natures and geodynamic mechanism(Halls,1982;Bleeker and Ernst,2006;Li et al.,2008;Ernst et al.,2010;Srivastava,2011;Hou,2012;Peng,2015;Peng et al.,2019).There are widespread late Paleozoic mafic dykes beside the huge of intermediate-acid igneous rocks in the TO,being an idea object to reveal the extensional events,tectonic evolution and the mantle nature and geodynamic processes.We present the ICPMS in situ zircon U–Pb dating,Lu-Hf and whole-rock Sr-Nd isotopes as well as the geochemistry data for these mafic dykes to better constraint their petrogenesis and mantle nature.New zircon U-Pb dating for 12 samples from the representative basic dykes and basalts yield three distinct stages of^332 Ma,316–302 Ma and 288–282 Ma,respectively.In which,the first stage of mafic dykes is mainly occurred in both East Tianshan Orogen(ETO)and West Tianshan Orogen(WTO),and composed of dolerite with minor basalts.The second stage of mafic dyke also can be found in both ETO and WTO.However,in contrast to the first stage of mafic dykes,they have relatively variable rock types from the dolerite/or gabbros to gabbroic diorite.The third stage of mafic dykes are slightly intermediate in composition,and chiefly consist of andesitic-basaltic dolerite with some diorites.They are widely developed not only in both ETO and WTO,but also in the Beishan area to the east of the ETO,indicating a large-scale mafic magmatism in Tianshan and adjacent areas.

Whole-Rock Geochemistry and Mineralogy of Triassic Montney Formation, Northeastern British Columbia, Western Canada Sedimentary Basin

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was used to analyze chemical elements—major, trace and rare earth elements (REE) concentrations, augmented with quantitative X-ray diffraction (XRD) analysis and thin-section petrography for mineralogical characterization of the Triassic Montney Formation in northeastern British Columbia, Western Canada Sedimentary Basin (WCSB). Results from this study indicate that integration of chemical elements with mineralogy shows affinity to the host lithologies. Evidently, chemical elements are the building blocks for minerals, thus, their significances in the interpretation of geological systems are unambiguous. Herein, major elements concentration such as Al, Fe, K, Mg, Ca, Mn in the samples analyzed from the Montney Formation are interpreted as: 1) indication of dolomitization and diagenesis;2) trace elements—Rb, Th, U, and Cs are related to the organic matter—kerogen in the clay component of the Montney Formation source rock;and 3) transition metals—Sc, V, Co, Cr, Zn show strong affinity with diagenesis in the study interval.

Whole-Rock Geochemistry and Mineralogy of Triassic Montney Formation, Northeastern British Columbia, Western Canada Sedimentary Basin

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was used to analyze chemical elements—major, trace and rare earth elements (REE) concentrations, augmented with quantitative X-ray diffraction (XRD) analysis and thin-section petrography for mineralogical characterization of the Triassic Montney Formation in northeastern British Columbia, Western Canada Sedimentary Basin (WCSB). Results from this study indicate that integration of chemical elements with mineralogy shows affinity to the host lithologies. Evidently, chemical elements are the building blocks for minerals, thus, their significances in the interpretation of geological systems are unambiguous. Herein, major elements concentration such as Al, Fe, K, Mg, Ca, Mn in the samples analyzed from the Montney Formation are interpreted as: 1) indication of dolomitization and diagenesis;2) trace elements—Rb, Th, U, and Cs are related to the organic matter—kerogen in the clay component of the Montney Formation source rock;and 3) transition metals—Sc, V, Co, Cr, Zn show strong affinity with diagenesis in the study interval.

小兴安岭-张广才岭成矿带洼兴Mo多金属矿区花岗岩成因及其对成矿的指示

洼兴Mo多金属矿床位于小兴安岭-张广才岭成矿带中段,是区域内新发现、正在勘探的斑岩型矿床。矿区内发育多期岩浆活动,锆石U-Pb定年结果表明,二长花岗岩(MG)、花岗闪长岩(GD)和黑云母二长花岗岩(BMG)的侵位年龄分别为177±1.9 Ma~174±1.2 Ma、170±1.9 Ma~169±2.1 Ma和172±1.5 Ma~172±1.4 Ma。三类花岗岩均以富硅(64.41%~77.77%)、富集大离子亲石元素、亏损P(P2O5=0.02%~0.21%)和Nb、Ta等高场强元素为特征。其铝饱和指数(A/CNK)在0.99~1.21之间,为准铝-弱过铝质、高钾钙碱性Ⅰ型花岗岩。全岩Nb/Ta值(7~13)与地壳可类比,三类花岗岩锆石εHf(t)值为3.9~18.8,表明其可能主要来源于新生地壳的部分熔融,暗色微粒包体(MMEs)的广泛发育暗示可能有一定的地幔物质加入。综合区域构造演化史,认为研究区花岗岩可能形成于佳木斯和松嫩地块碰撞晚期-碰撞后的构造背景。矿区花岗闪长岩和黑云母二长花岗岩分别与Cu-W、Mo-W矿化具有较好的空间耦合关系,且二者的侵位年龄与辉钼矿Re-Os加权平均年龄(169.0±2.2 Ma;MSWD=0.042)在误差范围内一致,暗示二者可能为成矿岩体,而二长花岗岩则为成矿前贫矿岩体。结合锆石U-Pb年代学、Hf同位素特征和岩相学特征综合分析认为,黑云母二长花岗岩与花岗闪长岩可能为同期岩浆不同演化程度的产物,更高的演化程度可能有利于岩浆中Mo的富集。矿区成矿期花岗岩(La/Yb)_(N)值较成矿前花岗岩显著降低,表明该地区在此期间发生了挤压-伸展的构造转换,此种转换可能有利于大规模岩浆-流体的累积和集中释放,从而有利于Mo矿化的形成。

Petrogenesis of volcanic rocks from Eastern Manus Basin: indications in mineralogy and geochemistry

To understand the petrogenesis and magma evolution history in the Eastern Manus Basin(EMB),geochemistry of pyroxene and plagioclase mineral phenocrysts in basaltic andesites and dacites were reported.The plagioclase-melt thermometry showed that,plagioclase in dacites crystalized in 1027.2–1028.5°C under 3.37–5.08 kbar,whereas in basaltic andesite was 1181.4–1187.0°C under 1.79–4.46 kbar.Pyroxene compositions and invariable La/Sm vs La values of whole rock powders indicate that lavas were erupted in rapid cooling rate and mainly controlled by fractional crystallization(FC).In addition,oscillatory zonings in plagioclase and pyroxene phenocrysts indicated small local perturbations and degassing episodes in the magma chamber.Some high Mg#clinopyroxene antecrysts were found in EMB lavas.The highest Mg#of parental EMB melts is 69,which falls into the range of initial partial melts from upper mantle peridotite source(68–75).In terms of isotopic compositions,the EMB lavas most likely originated from Indian-type MORB mantle which was infl uenced by subduction components.In details,the subduction components are mainly derived from the dehydration of a subducted altered oceanic crust,and the contribution of sediment infl uence is minor.The Pb isotopic compositions and end member modeling further suggest that the source of subduction components is more likely from the Pacifi c Plate instead of the Solomon Plate.

U-Th-Pb monazite and Sm-Nd dating of high-grade rocks from the Grove Mountains, East Antarctica: further evidence for a Pan-African-aged monometamorphic terrane

The Grove Mountains, 400 km south of the Chinese Antarctic Zhongshan Station, are an inland continuation of the Pan-African-aged （i.e., Late Neoproterozoic/Cambrian） Prydz Belt, East Antarctica. In this paper we carried out a combined U-Th-Pb monazite and Sm-Nd mineral-whole-rock dating on para- and orthogneisses from bedrock in the Grove Mountains. U-Th-Pb monazite dating of a cordierite-bearing pelitic paragneiss yields ages of 523 ？ 4 Ma for the cores and 508 ？ 6 Ma for the rims. Sm-Nd mineral-whole-rock isotopic analyses yield isochron ages of 536 ？ 3 Ma for a coarse-grained felsic orthogneiss and 507 ？ 30 Ma for a fine-grained quartzofeldspathic paragneiss. Combined with previously published age data in the Grove Mountains and adjacent areas, the older age of ~530 Ma is interpreted as the time of regional medium- to low-pressure granulite-facies metamorphism, and the younger age of ~510 Ma as the cooling age of the granulite terrane. The absence of evidence for a Grenville-aged （i.e., Late Mesoproterozoic/Early Neoproterozoic） metamorphic event indicates that the Grove Mountains have experienced only a single metamorphic cycle, i.e., Pan-African-aged, which distinguishes them from other polymetamorphic terranes in the Prydz Belt. This will provide important constraints on the controversial nature of the Prydz Belt.

赣中早古生代贵溪淡色花岗岩成因:来自全岩地球化学的约束

本文对赣中贵溪花岗岩进行了锆石U-Pb定年和岩石地球化学分析测试,探讨了其成因类型、源区性质、熔融机制和地球动力学背景。贵溪花岗岩岩性为白云母花岗岩,锆石U-Pb年龄为438±5 Ma。全岩主微量元素测试结果显示,贵溪花岗岩表现为高硅、高钾、贫镁、贫钙和强过铝质的特征。贵溪花岗岩LREE/HREE为7.35~10.4,(La/Yb)N为8.08~15.0,总体表现为轻稀土富集、重稀土亏损、轻重稀土分馏明显的特点,且相对富集Rb、Th、U和K,亏损Sr、Ba、Ta、Nb。相对较高的全岩Nb/Ta、Zr/Hf、K/Rb和Eu/Eu~*值以及较低的TE1,3值,说明贵溪花岗岩并非高分异花岗岩。较低的Zr+Nb+Ce+Y(<200×10^(-6))和Ga/Al值(<2.5)、高的A/CNK值(>1.2)以及富铝矿物白云母的出现和镁铁质暗色矿物的缺失说明贵溪花岗岩在岩石成因类型上应属于S型花岗岩。富集的全岩Nd同位素组成(ε_(Nd)(t)=-11)、高的Rb/Sr比值(>2)、中等的轻稀土饱和温度和锆饱和温度(699℃~794℃)以及贫钛(<0.2%)的特征,说明贵溪花岗岩的源区为古老变沉积岩,其形成于白云母脱水熔融作用。贵溪花岗岩形成于同碰撞环境而非俯冲环境,华南早古生代的构造属性应为陆内造山作用。

东昆仑东段各玛龙闪长岩年代学、地球化学特征及成因分析

各玛龙地区位于东昆仑造山带东段南部,该地区构造活动与岩浆活动强烈。本文以两件花岗闪长岩和两件英云闪长岩为研究对象,开展LA-ICP-MS锆石U-Pb年代学和岩石全岩元素组成研究,探讨岩石成因类型和岩浆源区特征,分析闪长岩的构造演化环境。研究结果表明:两件具有代表性的闪长岩样品成岩年龄分别为405.3±1.1 Ma和405.8±1.2 Ma,说明成岩时代为早泥盆世;4件闪长岩样品具有高硅、高铝、高碱、贫钙、贫镁、弱过铝质特征,属于弱过铝质高钾钙碱性系列岩石;4件样品中未发育S型花岗岩的代表性矿物,并且Rb/Sr值为0.32~0.43,均小于0.9,A/CNK值为0.98~1.09,均小于1.1,符合I型花岗岩的地球化学特征;通过分析La-La/Sm图解与(Zr+Nb+Ce+Y)-(Na_(2)O+K_(2)O)/CaO图解,同时结合Nb/Ta、Zr/Hf、Nb/U、Rb/Sr、Ti/Y、Ti/Zr值,可以得知各玛龙地区闪长岩是由地壳岩石部分熔融形成的,并且可能伴有幔源物质的参与。结合前人研究及(Y+Nb)-Rb图解与Rb/30-Hf-Ta*3图解可知,各玛龙地区闪长岩形成于早泥盆世东昆仑造山带的后碰撞伸展环境。

西藏班公湖-怒江缝合带中段东巧豆荚状铬铁矿地球化学特征及构造意义

东巧蛇绿岩位于班公湖-怒江缝合带中段北部,岩石组合为方辉橄榄岩、纯橄岩、铬铁岩、辉长岩、辉石岩、玄武岩和少量的硅质岩。东巧铬铁矿石的铬尖晶石化学成分表明岩体内同时存在高铬型铬铁矿(Cr#值为60.7~79.8,Mg#值为57.2~68.1)和高铝型铬铁矿(Cr#值为56.4~59.6,Mg#值为67.2~72.7)。高铬型铬铁矿体多呈稠密浸染状,部分为致密块状,而高铝型铬铁矿体规模较小,兼具稠密浸染状和稀疏浸染状。两种铬铁矿矿体的围岩都是纯橄岩,并且矿体以透镜状分布于方辉橄榄岩中。从纯橄岩包壳到条带浸染状铬铁矿石的过渡带中,铬尖晶石呈Cr#值增加(67.2~68.5),Mg#值降低(57.4~74.6)的特点,表明东巧地幔橄榄岩及其铬铁矿可能经历了一定程度的熔-岩反应。方辉橄榄岩中橄榄石Fo值为91.2~92.3,铬尖晶石Cr#值为70.2~75.1;纯橄岩橄榄石Fo值为92.7~92.9,铬尖晶石Cr#值为75.4~76.6,与班公湖-怒江缝合带上丁青、切里湖、依拉山等岩体较为相似,表明东巧地幔橄榄岩形成条件可能与其相近。东巧地幔橄榄岩具有弧前地幔橄榄岩稀土元素特征,微量元素配分模式与Izu-Bonin-Mariana具有极高相似性,指示东巧蛇绿岩可能形成于板块俯冲消减带上盘海底扩张环境。铬铁矿的铂族元素(PGE)配分模式与罗布莎高铬铬铁矿相似,具有富集IPGE、亏损PPGE的特点。对东巧地幔橄榄岩及其铬铁矿平衡熔体进行分析,高铬型铬铁矿形成于俯冲带上岛弧环境(SSZ型)的弧前盆地,高铝型铬铁矿形成于洋中脊型环境(MOR型),并对比班-怒带毗邻岩体,指示东巧地幔橄榄岩及其铬铁矿经历了MOR→SSZ的多期次演化过程。

滇西首例火成碳酸岩的发现与厘定

火成碳酸岩(又称碳酸岩)是由地幔派生的富碳酸盐矿物且贫硅的火成岩石,地表出露较少。碳酸岩是研究地幔性质及其演化过程的岩石“探针”,并且蕴藏着丰富的稀土和铌等关键金属矿产资源。因此,对它的研究具有重要的科学和经济价值。本次工作首次在云南保山龙陵地区发现火成碳酸岩岩体,规模较大,岩体出露面积约为60000m 2。出露于保山地块与腾冲地块之间的龙陵-潞西褶皱带内。新发现的碳酸岩主要由方解石和白云石等矿物组成,其次还含有大量的磷灰石、磁铁矿、黑云母、辉石、独居石和斜锆石等副矿物。结合岩相学、矿物学和全岩地球化学组成,可将新发现的碳酸岩划分为钙质、镁质和含铁钙质三类。不同岩性的CaO(29.57%~51.66%)、Fe_(2)O^(T)_(3)(0.72%~21.15%)和MgO(1.76%~16.90%)含量变化大。微量元素特征显示,碳酸岩总体富集Sr(3431×10^(-6)~9753×10^(-6))、Ba(197×10^(-6)~2428×10^(-6))、Pb(14.4×10^(-6)~425×10^(-6))和∑REE(841×10^(-6)~2341×10^(-6))等大离子亲石元素,相对亏损Nb(1.09×10^(-6)~12.48×10^(-6))、Ta(0.12×10^(-6)~4.74×10^(-6))和Hf(0.07×10^(-6)~7.85×10^(-6))等高场强元素。稀土配分模式为右倾型,(La/Yb)N比值介于58~104之间,富集LREE,具有弱铕负异常(δEu=0.68~0.74)。碳酸岩中主要造岩矿物方解石、白云石和磷灰石也表现出与全岩相似的元素地球化学特征。碳酸盐矿物的δ^(13)C V-PDB值(-7.45‰~-3.54‰)大多落入“初始火成碳酸岩”范围,但δ^(18)O V-SMOW值(10.79‰~20.06‰)偏高,很可能源于岩浆期后热液蚀变。上述全岩、矿物化学和C-O同位素特征与全球大多数碳酸岩基本一致,证实坡头岩体为典型的火成碳酸岩。钙质碳酸岩中斜锆石的LA-ICPMS测年结果显示,其U-Pb等时线谐和年龄为160.7±2.0Ma(MSWD=1.8),^(206)Pb/^(238)U加权平均年龄为159.7±1.8Ma(MSWD=2.4),表明其形成于中侏罗世,为三叠纪碰撞造山作用后的岩浆活动产物。坡头碳酸岩的发现与厘定将有助于揭示所在区域地幔特征,其关键金属成矿潜力也值得进一步的探究。

岩土成层条件下抗滑桩计算的改进有限差分法

滑坡治理工程中抗滑桩可能布置于层状土层、层状岩层,或岩、土成层等各种地质条件下,现行规范对于该问题建议将成层地基按加权平均法换算成等效的当量地基系数,但对于地层差异性较大的岩土成层地基其适用性有待研究。为解决这一问题,基于Euler-Bernoulli梁理论建立抗滑桩受荷段、嵌固段整体受荷分析模型,采用改进有限差分法提出抗滑桩全桩内力求解的统一矩阵运算式,避免常规有限差分方法将桩身分为受荷段和嵌固段及利用滑面处连续性条件求解的复杂迭代过程;基于2个边坡工程抗滑桩治理案例,证明改进有限差分法对岩土成层条件下抗滑桩分析的可靠性,计算用时仅需1.2 s左右,相比已有方法进一步提高抗滑桩分析设计的计算效率。

Lu-Hf同位素体系及其岩石学应用

Lu-Hf是近几年来发展极为迅速的一门同位素定年和地球化学示踪技术。本文对这一同位素体系的发展历史、岩石学应用和存在的问题进行了全面的评述,对目前常见的样品溶解、质谱测定和激光剥蚀技术进行了全面介绍。虽然Lu-Hf同位素的发展历史可划分为TIMS、hot-SIMS、MC-ICPMS三个阶段,但MC-ICPMS仪器的出现,使Hf同位素发展速度明显加快。在介绍了Lu-Hf同位素的基本地球化学行为和基本原理之后,本文对这一同位素体系在岩石学上的应用作了全面的介绍,内容包括含石榴石和磷灰石岩石的同位素定年、早期大陆地壳形成与演化、不同端元地幔的性质及成因、岩浆作用过程的Hf同位素鉴别、区域地球动力学演化、变质作用过程中的Hf同位素变化等。最后对Lu的衰变常数、测定标准(JMC475溶液和固体锆石/斜锆石标准)的Hf同位素组成及Hf同位素的封闭温度等问题进行了讨论。

吐哈盆地台北凹陷侏罗系煤系全油气系统特征

基于吐哈盆地中下侏罗统近源勘探最新成果,以全油气系统理念和思路重新认识台北凹陷侏罗系水西沟群烃源岩、储层条件和生储盖组合,深入解析煤系全油气系统。结果表明:(1)水西沟群八道湾组、西山窑组煤系烃源岩和三工河组泥质烃源岩表现为长时间生烃、具有多个生烃高峰和油气兼生的特点,为侏罗系煤系全油气系统提供充足的油气来源;(2)多期浅水辫状河三角洲—浅湖沉积为斜坡区、洼陷区发育常规砂岩、致密砂岩、煤岩、泥页岩等多类型储层,为油气成藏聚集提供多种储集空间;(3)3期油气充注与构造演化、多类型储层有效配置,形成常规-非常规油气序次成藏聚集的特点,从构造高部位到洼陷区发育远源常规构造油气藏、构造-岩性油气藏,近源低饱和度构造-岩性油气藏和源内致密砂岩气聚集、煤岩储层气、页岩油等类型油气聚集。其中,源内致密砂岩气、煤岩气是当前勘探拓展的重点领域,洼陷区页岩油气值得未来探索研究。煤系全油气系统新认识将进一步丰富完善全油气系统地质理论,为吐哈盆地油气资源的整体勘探部署提供新思路。

辽宁盖县梁屯-矿洞沟碱性正长岩杂岩体的U-Pb和Sm-Nd年龄及其地质意义

辽宁梁屯 -矿洞沟杂岩体主要由辉石正长岩、霓辉正长岩和霓辉角闪正长岩等碱性岩石组成 ,具有全岩 Rb- Sr等时线年龄 186 6± 115 Ma和 ISr=0 .70 4 9的同位素特征 ,是我国目前报道的最古老的碱性正长岩类。本文报道了该岩体的锆石U- Pb和全岩 Sm- Nd同位素测试资料 ,获得了锆石 U- Pb同位素年龄为 185 7± 2 0 Ma、Sm- Nd等时年龄为 1787± 180 Ma、εNd(t) =- 4 .8～ - 5 .0的数据。它们反映出该杂岩体形成年龄的上限为 185 7± 2 0 Ma、下限不小于 1787± 180 Ma,来源于富集地幔物质。基于这些数据并结合区域地质资料分析 ,作者提出了华北地台北缘古元古宙存在有富集地幔储库 ,以及辽河群主体形成于 190 0

湖相碳酸盐岩烃源岩有机显微组分分类及其岩石学特征——以酒西盆地为例

酒西盆地主力烃源岩为下白垩统下沟组和赤金堡组暗色半深湖相-深湖相的白云质泥岩和泥质白云岩,是典型的湖相碳酸盐岩烃源岩。通过对酒西盆地下白垩统二百多块湖相碳酸盐岩烃源岩详细的有机岩石学研究,解剖了湖相碳酸盐岩烃源岩中有机质的赋存形式,揭示了藻纹层为有机质纹层的主要发育形式,其与富泥晶白云石纹层和富粘土纹层构成湖相碳酸盐岩烃源岩特有的"三元式纹层"沉积结构,系统总结了各显微组分的光性、成因、生烃性及分布规律,提出了以全岩和干酪根为基础的湖相碳酸盐岩有机显微组分分类方案,首次鉴定出对酒西盆地油气有贡献的主要生烃组分为腐泥无定形体、腐殖无定形体以及浮游藻类体、孢粉体、壳屑体五种有机显微组分。

湘东锡田钨锡矿区成岩成矿时代研究

湘东锡田钨锡矿是近年来在找矿上有重大突破的地区。笔者在分析前人资料的基础上,应用Rb-Sr全岩法和Re-Os辉钼矿法对锡田花岗岩及产于其中的云英岩石英脉型钨锡矿进行了精确定年。结果表明:锡田岩体主体、补体和晚期花岗岩形成年龄分别为:165±16Ma(2σ)、151±24Ma(2σ)、114±14Ma(2σ);早期云英岩石英脉型钨锡矿辉钼矿Re-Os等时线年龄为150±2.7Ma。研究显示该区可能还残留有印支期花岗岩,钨锡成矿与燕山期花岗岩侵入活动有关。不同类型钨锡矿生成顺序为:矽卡岩型→早期云英岩石英脉型→晚期云英岩石英脉型→破碎带蚀变岩型。

江西雅山花岗岩长石中磷的分布及意义

雅山富氟高磷花岗岩具较高的全岩磷含量（０．１５％～０．５５％），长石是磷的主要赋存矿物，磷以ＰＡｌＳｉ－２替换方式进入长石结构中。各种结晶习性的长石的磷含量各不相同。早世代钠长石和雪球结构中钠长石包裹体的结晶较早，平均磷含量分别为０．１８％和０．１９％，而晚世代钠长石和环带钾长石中钠长石嵌晶的结晶稍晚，具较高的平均磷含量（分别为０．２５％和０．２３％）。钾长石的磷含量相对于钠长石总体上较低，早期结晶的雪球结构主晶钾长石和环带钾长石的磷含量最低，分别为０．０４％和０．０２％，晚期细粒钾长石的平均磷含量略高（０．１９％）。长石对全岩磷的贡献率还与磷锂铝石等磷酸盐副矿物是否达到饱和有关，当无磷锂铝石结晶时，长石磷的贡献率约为７６％，反之则约为３１％。

安徽沙坪沟钼矿区中酸性侵入岩期次研究——年代学及岩石化学约束

近年来，随着大别造山带内沙坪沟、汤家坪、千鹅冲等多个大型一超大型钼矿床的陆续发现，大别造山带钼金属成矿潜力引起了地学界的广泛关注。沙坪沟钼矿床位于大别造山带内，地处安徽省金寨县银山地区，是近年来发现的世界第二大斑岩型钼矿床。沙坪沟钼矿区广泛发育不同类型中酸性侵入岩，包括二长花岗岩、花岗闪长岩、石英二长岩、正长岩、钾长花岗斑岩等，前人对沙坪沟钼矿区内侵入岩的成岩时代、形成及演化过程的研究仍有待深入。本次工作在详细野外地质调查基础上，开展了沙坪沟钼矿区主要中酸性侵入岩年代学和岩石地球化学研究工作。通过锆石LA-ICP MSU-Pb定年方法，确定了二长花岗岩、花岗闪长岩、正长岩和钾长花岗斑岩成岩时代分别为136.3±1.6Ma、127.5±2.9Ma、117.2±1.2Ma和112.2±1.2Ma；结合前人的研究成果和侵入岩野外地质特征，提出矿区内中酸性侵入岩的成岩时代可划分为136～125Ma和124～112Ma两个阶段。中酸性侵入岩的岩石地球化学特征显示，由第一阶段到第二阶段，岩浆系列由高钾钙碱性系列向钾玄岩系列、钙碱性系列向碱性系列转变，岩浆性质由氧化性向还原性变化，岩浆源区由壳幔型源区向壳型源区演化，成岩背景由构造格局转变的伸展背景向稳定的板内背景过渡。高钾、高碱、高分异、偏还原、壳型源区，形成于稳定板内背景的侵入岩可能更有利于形成大型斑岩型钼矿床。

滇西北羊拉铜矿矿区花岗岩成因及其构造意义

羊拉铜矿位于金沙江缝合带中段,贝吾、里农和路农岩体在矿区内从北向南呈线状分布。3个岩体主要岩性为花岗闪长岩,具有相似的地球化学和Sr-Nd同位素组成特征,反映它们可能具有相同岩浆源区。岩体具高的SiO2(64%～73%)、较高的K2O(2.15%～4.05%)和低的P2O5(0.04%～0.11%)含量,δ(里特曼指数)=1.4～2.4,铝饱和指数(摩尔Al2O3/(CaO+Na2O+K2O))为0.92～1.11。同时3个岩体均富集Rb、Th、U、Pb和LREE等元素,显著亏损Nb、Ta、Ti和P等元素。10000Ga/Al比值(1.7～2.1)较典型A型花岗岩偏低,Eu负异常不明显,这些特征表明3个岩体属于准铝-弱过铝质的、高钾钙碱系列I型花岗岩。与区域上大陆地壳物质相比(如临沧黑云母二长花岗岩和川西沙坝麻粒岩),贝吾、里农和路农岩体具有相对低的(87Sr/86Sr)i(0.7078～0.7105)和相对高的εNd(t)(-5.1～-6.7),并具古老的Nd同位素二阶段模式年龄(tDM2=1.5Ga)。结合花岗岩体内部发育大量的同时代的暗色微粒包体(MME),认为岩浆源区存在幔源物质的加入。区域地质背景分析表明,贝吾、里农和路农岩体很可能是在中咱微陆块与昌都-思茅微陆块碰撞的晚期或后碰撞的动力学背景之下,由底侵的幔源基性岩浆及其诱发的中下地壳长英质岩浆在深部岩浆房混合,并经一定程度的分离结晶作用而形成。

湖南千里山花岗岩体的Nd－Sr同位素及岩石成因研究

本文利用Ｒｂ－Ｓｒ等时线方法测得第一阶段似斑状黑云母花岗岩、第二阶段等粒黑云母花岗岩和第三阶段花岗斑岩的成岩年龄分别为（１５２±９）×１０￣６ａ、（１３７±７）×１０￣６ａ～（１３６±６）×１０￣６ａ和（１３１±１）×１０￣６ａ。Ｓｒ－Ｎｄ同位素资料表明各阶段花岗质岩石均基本上源于地壳物质的重熔。与钨多金属矿化有关的似斑状黑云母花岗岩和等粒黑云母花岗岩属同一岩浆体系分异演化的产物，其钕模式年龄（ｔ＿（ＤＭ）＝２３０７×１０￣６ａ）反映出成岩物质来自早元古宙地层的重熔。与铅－锌－银矿化有关的花岗斑岩的钕模式年龄（ｔ＿（ＤＭ）＝１２８４×１０￣６～１５７８×１０￣６ａ）示意出其成岩物质来自中元古宙地层的重熔。