湘东北栗山铅锌铜矿床二长花岗岩岩石成因及其氧逸度对成矿的指示意义

栗山铅锌铜矿床位于江南造山带多金属成矿带中段,是湘东北地区近几年发现的一大型矿床。本文对矿区内的黑云母二长花岗岩和二云母二长花岗岩进行了岩石地球化学、Sr-Nd同位素和黑云母矿物成分研究。岩石地球化学特征显示,两种二长花岗岩均属于高钾钙碱性系列。其中,黑云母二长花岗岩属于正常S型花岗岩,富集Rb、Th、K大离子亲石元素,亏损Ba、Nb、Ta、Sr、P、Ti高场强元素,有弱的Eu负异常,源区岩石为变质杂砂岩;二云母二长花岗岩属于分异的S型花岗岩,富集Rb、Th、U、K大离子亲石元素,亏损Ba、Nb、Sr、P、Ti高场强元素,Eu负异常大于前者,源区岩石为变泥质岩和少量变质杂砂岩。黑云母二长花岗岩的(⁸⁷Sr/⁸⁶Sr)_i值在0.7143～0.7159之间,ε_Nd(t)值介于-9.4～-8.5,两阶段模式年龄t_DM2变化范围为1631～1703 Ma;二云母二长花岗岩的(⁸⁷Sr/⁸⁶Sr)_i值在0.7156～0.7...     

内蒙古维拉斯托矿床花岗岩类SHRIMP年代学及Hf同位素研究

维拉斯托铜多金属矿床地处中亚造山带和大兴安岭造山带的叠加复合部位,该矿床花岗岩类锆石SHRIMP U-Pb测年结果显示为(298.0±2.5)Ma、(308.3±4.2)Ma、(313.9±3.4)Ma和(320.5±4.1)Ma,表明该矿区花岗岩类的成岩时代为晚石炭世。岩石地球化学特征表明它们为岩浆弧活动的产物。除花岗闪长岩样品锆石的εHf(t)为-4.1～+4.08外,其他3件黑云母花岗岩、黑云母二长花岗岩、石英闪长岩样品锆石ε_Hf(t)为正值,为+0.4～+9.9,锆石Hf模式年龄的峰值与古亚洲洋发育的时间较为一致,暗示矿区花岗岩类源区物质主要为俯冲的古亚洲洋壳以及少量前寒武纪地壳。矿区花岗岩类系统研究为探讨晚古生代兴蒙造山带的演化过程提供了基础资料,为该铜多金属矿床的成因研究提供了新的证据。     

鄂东南地区程潮大型矽卡岩型铁矿区岩体成因探讨

湖北程潮铁矿是鄂东南矿集区内最大的矽卡岩型铁矿床。为了系统研究矿区内不同侵入体的成因,对程潮矿区内不同时代的侵入体进行了矿物学、地球化学和Sr-Nd-Pb同位素研究。矿区内花岗岩、石英二长斑岩、闪长岩中的黑云母成分特征暗示它们均为壳幔物质混合成因的镁质黑云母;与成矿相关的花岗岩、石英二长斑岩中原生黑云母矿物学成分显示出原始岩浆具有高氧逸度的特征,高氧逸度为磁铁矿的形成提供了有利条件。岩石地球化学特征研究表明,不同类型的岩石都具有富钾和准铝质的特征,富集Rb、Ba、K等大离子亲石元素和轻稀土元素,亏损Nb、Ta、Ti等高场强元素。矿区岩石的(⁸⁷Sr/⁸⁶Sr)_i值为0.705 0~0.709 1,ε_Nd(t)值为-14.16~-6.95,²⁰⁶Pb/²⁰⁴Pb值为17.636~18.919,²⁰⁷Pb/²⁰⁴Pb值为15.451~15.613,²⁰⁸Pb/²⁰⁴Pb值为37.833~39.556。矿物学、地球化学、Sr-Nd-Pb同位素特征暗示矿区岩体为富集地幔发生部分熔融并同化混染了不同比例下地壳物质的产物,早期闪长岩（（140±1） Ma）比晚期花岗岩和石英二长斑岩（（128±1） Ma）的源区有更多的地幔成分,花岗岩和石英二长斑岩与闪长岩具有相近的锆石饱和温度（平均值分别为783、788、765℃）。     

北喜马拉雅恰芒巴二云母花岗岩的年龄及形成机制

恰芒巴二云母花岗岩体位于特提斯喜马拉雅的西部, 岩石发育片麻状构造, 主要矿物组成为石英、钾长石、白云母和黑云母。LA-MC-ICP-MS U-Pb定年显示, 锆石年龄分布范围为35.1~17.3 Ma, 暗示较长时间的深熔作用过程, 其中最年轻的年龄(18.1±0.4 Ma)代表了花岗岩的最终结晶年龄。地球化学分析表明, 岩石具有高的SiO₂(73.06%~73.79%)、Al₂O₃(14.73%~15.06%)和CaO(1.18%~1.24%)含量, 以及高的K₂O/Na₂O值(1.16~1.25)和A/CNK值(1.16~1.20), 属于高钾钙碱性过铝质花岗岩。岩石强烈富集Rb、Th、U和K, 而亏损Ba、Nb、Sr和Zr, 轻重稀土分馏较强(La/Yb)_N=9.98~11.35, 并显示较弱的负Eu异常(δEu=0.70~0.74)。(⁸⁷Sr/⁸⁶Sr)_i和ε_Nd(t)值分别为0.742 298~0.743 092和-14.1~-14.0, 可与大喜马拉雅结晶杂岩(GHC)中变质沉积岩对比, 推测源岩为GHC变质沉积岩或与之成分相当的岩石。岩石(⁸⁷Sr/⁸⁶Sr)_i值较低而Sr浓度较高, 随着Ba浓度的增加, Rb/Sr值基本不变, 与水致白云母部分熔融的趋势一致, 推测恰芒巴二云母花岗岩可能是水致白云母部分熔融的产物, 部分熔融作用可能与藏南拆离系的活动密切相关。     

印尼北苏拉威西中部～10 Ma闪长岩的岩石成因及对西里伯斯海向南俯冲的启示

苏拉威西岛位于欧亚、太平洋和印度-澳大利亚板块的交汇处,经历了复杂的构造演化历史,保存了大量中-新生代岩浆记录。本研究对北苏拉威西中部闪长岩开展了锆石U-Pb年代学和Lu-Hf同位素、全岩元素-同位素地球化学研究。研究显示,闪长岩锆石U-Pb年龄为10.32±0.44 Ma和9.87±0.11 Ma,形成于晚中新世。样品SiO₂含量为53.81%～59.90%,MgO为3.27%～4.27%,K₂O为0.48%～1.22%,A/CNK=0.86～0.92,Mg^#为47～49,属高镁中钾钙碱性闪长岩。该闪长岩以富集大离子亲石元素和轻稀土元素、亏损高场强元素为特征,具明显Nb-Ta和Ti负异常,轻微Eu负异常（Eu/Eu^*=0.78～0.96）。闪长岩(⁸⁷Sr/⁸⁶Sr)_i值变化于0.70498～0.70509之间,ε_Nd（t）值变化于+5.6～+5.7之间,锆石原位ε_Hf（t）值为+11.2...     

甘肃北山南带沙枣园复式岩体年代学、地球化学特征及其构造意义

北山南带沙枣园复式岩体由中细粒黑云母花岗闪长岩、细粒黑云母石英闪长岩、中粒黑云母二长花岗岩和中粗粒黑云母正长花岗岩4个岩相单元组成。LA-ICP-MS锆石U-Pb定年结果表明,中细粒黑云母花岗闪长岩、细粒黑云母石英闪长岩和中粒黑云母二长花岗岩侵位于晚二叠世(252.1±1.9Ma、252.2±2.1Ma和248.8±3.5Ma),为海西晚期的产物;而中粗粒黑云母正长花岗岩侵位于早三叠世(246.4±2.0Ma),为印支早期的产物。该花岗质岩石均具有稀土元素的球粒陨石标准化配分曲线呈右倾型,轻重稀土分馏大,轻稀土富集且分异明显,而重稀土亏损且分异不显著特征。中细粒黑云母花岗闪长岩和细粒黑云母石英闪长岩具有较高的SiO_2、Al_2O_3和Na_2O含量,以及较低的MgO含量,强烈富集Sr而亏损Yb和Y,具轻微的铕异常(δEu=0.75～1.16),表现出典型的埃达克岩特征;中粒黑云母二长花岗岩和中粗粒黑云母正长花岗岩总体富硅(SiO_2)、富钾(K_2O)、富碱(K_2O+Na_2O),Al_2O_3含量中等,铕分别呈现负异常(δEu=0.45～0.73)和强负异常(δEu=0.02～0.08)。年代学及地球化学特征研究表明:①中细粒黑云母花岗闪长岩和细粒黑云母石英闪长岩属准铝质-弱过铝质的钙碱性Ⅰ型花岗岩,并具有典型的埃达克岩特征,中粒黑云母二长花岗岩属弱过铝质的高钾钙碱性Ⅰ型花岗岩,中粗粒黑云母正长花岗岩属弱过铝质的高钾钙碱性A2型花岗岩;②中细粒黑云母花岗闪长岩、细粒黑云母石英闪长岩和中粒黑云母二长花岗岩的岩浆来源于下地壳玄武质岩石部分熔融源区,并在上升过程中混染了下地壳物质,而中粗粒黑云母正长花岗岩的岩浆来源于年轻地壳中富含黑云母的变质泥岩部分熔融源区;③中细粒黑云母花岗闪长岩、细粒黑云母石英闪长岩和中粒黑云母二长花岗岩是俯冲-碰撞构造背景条件下的岩浆产物,而中粗粒黑云母正长花岗岩是同碰撞-碰撞后构造背景条件下的岩浆产物。     

中祁连西段黑沟梁子花岗岩的锆石U-Pb同位素年龄及成因

黑沟粱子花岗岩岩体为中祁连山带两段野马南山巨量花岗岩的一部分,出露于野马山南北缘,岩性为黑云母二长花岗岩。δ值、NK／A值、A／NCK值、Eu负异常、δEu值、ACF图解、⁸⁷Sr/⁸⁶Sr比值、εS_r、¹⁴⁷Sm／¹⁴⁴Nd比值、²⁰⁷Pb/²⁰⁴Pb比值、ENd值等岩石化学和同位素特征表明黑沟粱子花岗岩属钙碱性过铝质岩系,浆来源于地壳物质的重熔,具S型花岗岩特点。通过对黑沟梁子花岗岩的颗粒级锆石U-Pb同位素测年,获得²⁰⁶Pb/²³⁸U表面年龄统计权重平均值为(444±17)Ma。w(Nb)-w(Y)和w(Rb)一w(Y+Nd)图和R₁-R₂图解上两个样点均落入同碰撞花岗岩区,结合前人研究成果可以确定该岩体形成于板块碰撞阶段。该岩体的锆石U-Pb年龄的确定和成因的探讨对于深入研究祁连造山带的构造演化提供了一条重要的地质信息。     

新疆巴尔鲁克地区加曼铁列克得岩体花岗闪长岩的地球化学和年代学研究

本文对新疆巴尔鲁克地区加曼铁列克得岩体花岗闪长岩进行了锆石U-Pb年代学、岩石地球化学和Sr-Nd-Hf同位素研究,探讨其岩石类型、构造背景和岩石成因。LA-ICP-MS锆石U-Pb定年表明,花岗闪长岩的成岩年龄为318.2±3.6 Ma,形成时代为晚石炭世。岩石高硅、富钠,碱含量中等,Mg#介于53.9～56.6,属于准铝质钙碱性花岗岩类（A/CNK = 0.91～0.97）,轻重稀土分馏较明显且富集轻稀土（La_N/Yb_N = 8.55～10.10）,Eu异常不明显,富集大离子亲石元素Ba、K、Sr,亏损高场强元素Nb、Ta、P、Ti。同位素特征显示,岩石具有低I_Sr值（0.703 82～0.704 24）、正ε_Nd（t）值（+6.96～+7.74）,年轻的t_DM1值为0.74～0.61 Ga,锆石ε_Hf（t）值为+12.6～+14.7,t_DM2为519～396 Ma。综合地质、地球化学和年代学特征,认为加曼铁列克得花岗闪长岩为未分异的Ⅰ型花岗岩,形成于晚石炭世俯冲背景下的岛弧环境,可能是由流体参与的新元古代玄武质洋壳部分熔融的产物,岩浆上升过程中受到楔形地幔物质的混染。     

东昆仑昆中缝合带的活化：来自石炭纪花岗岩的证据

在东昆仑西段工作程度较低的阿克苏河地区,首次识别出石炭纪侵入岩浆活动。阿克苏复式岩体位于昆中断裂带西段,锆石LA-ICP-MS定年显示,花岗闪长斑岩结晶年龄为361±2.4 Ma,二长花岗岩结晶年龄为357.5±2.8 Ma,花岗闪长岩结晶年龄为354±4.3 Ma,代表这些岩体侵位于晚泥盆世—早石炭世(临近昆中缝合带西部),该阶段岩浆事件此前未见公开报道。主量元素分析显示,此套花岗闪长斑岩、二长花岗岩和花岗闪长岩具有富Si、Al、K的特征,为高钾钙碱性过铝质系列;微量和稀土元素分析显示,岩石具有轻、重稀土元素分馏和轻稀土元素富集及负Eu异常特征,富集大离子亲石元素(LILE)Th、U、Rb、K;亏损高场强元素(HFSE)Nb、P、Ti等。锶同位素分析显示,⁸⁷Sr/⁸⁶Sr初始值为0.70612～0.71009,ε_Nd(t)为-7.1～-5.1,T_DM2为1.51～1.69 Ga。综合岩石-矿物特征和地球化学分析,这些岩石应该属于I型花岗岩,主要为受幔源岩浆作用后地壳物质重熔的结果,指示东昆仑昆中...     

安庆早白垩世洪镇花岗岩成因及其对基底构造格局的启示

花岗岩可以有效示踪大陆基底物质,并区分具有不同地壳结构和演化历史的构造块体。洪镇花岗岩位于长江中下游地区江北A型花岗岩带的西延位置,距离郯庐断裂带约30 km。锆石SIMS定年表明,安庆怀宁县洪镇花岗岩形成于126.2±2.0 Ma,与长江中下游A型花岗岩以及大别造山带I型花岗岩的形成时代一致。洪镇花岗岩高硅、富钾,属于高钾钙碱性系列I型花岗岩。其富集轻稀土元素和大离子亲石元素,相对亏损中稀土元素和高场强元素,经历了角闪石为主的结晶分异。洪镇花岗岩具有较为富集的Sr—Nd—Hf同位素,和低放射性成因Pb同位素组成,其n(⁸⁷Sr)/n(⁸⁶Sr)(t)为0.7065～0.7066,ε_Nd(t)值为-10.9～-12.0,锆石ε_Hf(t)为-6.7～-13.2,n(²⁰⁶Pb)/n(²⁰⁴Pb)(t)、n(²⁰⁷Pb)/n(²⁰⁴Pb)(t)和n(²⁰⁸Pb)/n(²⁰⁴...     

北山野马井地区泥盆纪富钾酸性岩浆岩地球化学特征及其地质意义

为了理清北山南部晚古生代构造演化过程,对野马井地区的二长花岗岩与流纹岩进行了岩石学、全岩主微量元素地球化学、锆石U-Pb年代学及Hf同位素等研究.LA-ICP-MS锆石U-Pb定年结果表明二长花岗岩与流纹岩的就位年龄分别为402.7±2.4 Ma与392.9±2.5 Ma.二者均为富钾钾质岩浆岩,呈现过铝质-强过铝质,轻重稀土弱到中等分馏且相对富集轻稀土,二长花岗岩呈现无或弱的负Eu异常,流纹岩呈现较明显的负Eu异常,二者均富集Rb、Th、U、Pb等,亏损Nb、Ta、Ba、Sr、Ti等,为I型酸性岩浆岩.二长花岗岩与流纹岩的锆石ε_Hf（t）值介于-2.2~+6.8,对应Hf模式年龄（t_DM2）为962~1 533 Ma;指示二者主要由中元古代陆壳物质熔融所形成.依据野马井地区泥盆纪富钾酸性岩浆岩的地球化学特征,结合该区域其他地质资料,可推测其为后碰撞构造环境的产物.      

Geochronological, geochemical and geothermal constraints on petrogenesis of the Indosinian peraluminous granites in the South China Block: A case study in the Hunan Province

The Indosinian granites in the South China Block (SCB) have important tectonic significance for the evolution of East Asia. Samples collected from Hunan Province can be geochemically classified into two groups. Group 1 is strongly peraluminous (A/CNK > 1.1), similar to S-type granites, and Group 2 has A/CNK = 1.0–1.1, with an affinity to I-type granites. Group 1 has lower FeOt, Al₂O₃, MgO, CaO, TiO₂ and ε_Nd(t) values but higher K₂O + Na₂O, Rb/Sr, Rb/Ba and ⁸⁷Sr/⁸⁶Sr(t) than those of Group 2. Samples of both groups have similar LREE enriched pattern, with (Eu/Eu) = 0.19–0.69, and strongly negative Ba, Sr, Nb, P and Ti anomalies. Geothermobarometry study indicates that the precursor magmas were emplaced at high-level depth with relatively low temperature (734–827 °C). Geochemical data suggest that Group 1 was originated from a source dominated by pelitic composition and Group 2 was from a mixing source of pelitic and basaltic rocks with insignificant addition of newly mantle-derived magma. Eight granitic samples in Hunan Province are dated at the cluster of 243–235 and 218–210 Ma by zircon U–Pb geochronology. Together with recent zircon U–Pb ages for other areas in the SCB, two age-clusters, including 243–228 Ma just after peak-metamorphism ( 246–252 Ma) and 220–206 Ma shortly after magma underplating event (224 Ma), are observed. It is proposed that in-situ radiogenic heating from the over-thickened crust induced dehydrated reaction of muscovite and epidote/zoisite to form the early Indosinian granites in response to the isostatic readjustments of tectonically thickened crust. Conductive heating from the underplating magma in the postcollisional setting triggered the formation of late Indosinian granites. Such a consideration is supported by the results from FLAC numerical simulation.     

Pan-African Alkali Granitoids from the Sør Rondane Mountains, East Antarctica

Alkali granitoids (500-550 Ma) representing a prominent Pan-African magmatic event are widely distributed in the Sør Rondane Mountains, Dronning Maud Land, East Antarctica. Geochemically, they are granitic to syenitic in composition and show an alkaline affinity of A-type granites. They are characterized by high K₂O+Na₂O (7-13 wt%) and K₂O/Na₂O (1-2), low to intermediate Mg#, wide ranges of SiO₂ (45-78 wt%), Sr (20-6500 ppm) and Ba (40-13000 ppm) and have Nb and Ti depletion in the primitive mantle normalized diagram. The granitoids are subdivided into Group I granites, Group II granites, Lunckeryggen Syenitic Complex and Mefjell Plutonic Complex. The Group I granites have higher Mg#, Sr/Ba, Sr/Y, (La/Yb)_N and LREE/HREE, lower A/CNK, SREE and initial ⁸⁷Sr/⁸⁷Sr ratios and lack Eu anomalies compared to those with negative Eu anomalies in the Group II granites. The syenitic rocks from the Mefjell Plutonic Complex are higher in alkali, Ga, Zr, Ba, and have lower Mg#, Rb, Sr, Nb, Y, F and LREE/HREE with positive Eu anomaly, whereas the granites from the Mefjell Plutonic Complex have high LREE/HREE ratios with negative Eu anomaly. The Lunckeryggen syenitic rocks have intermediate Mg#, higher K₂O, P₂O₅, TiO₂, Fe₂O₃/FeO, Ba, Sr/Y and LREE/HREE ratios with lack of Eu anomalies and are lower in Al₂O₃, Ga, Y, Nb and Rb/Sr ratios. Based on chemical characteristics combined with isotopic data, we suggest that the Lunckeryggen syenitic body and Group I granitic bodies may be derived from the mantle-derived hot basic magma by fractional crystallization with minor assimilation. We also suggest that the Group II granites may be derived from assimilation with crustal rocks to varing degrees and then fractional crystallization in higher crustal levels (ACF model). The Mefjell Plutonic Complex seems to be derived from a heterogenetic magma source compared with other granitoids from the Sør Rondane Mountains. The syenitic rocks in the Mefjell Plutonic complex have a unique source (iron-enriched) and have a chemical affinity with the charnockites in Gjelsvikjella and western Mühlig-Hofmannfjella, but not like the Yamato syenites in adjacent areas.     

桂西南早中生代流纹岩年代学、地球化学特征及地质意义

印支期桂西南地区处于多板块构造交汇地带,其岩浆构造演化存在很大的争议。对桂西南十万大山盆地两侧酸性火山岩进行了系统的锆石年代学、全岩地球化学及Sr-Nd同位素地球化学研究。结果表明,十万大山盆地两侧酸性火山岩LA-ICP-MS锆石U-Pb年龄为240.5~248.4 Ma,形成于早三叠世。岩性主要为流纹岩,具有高SiO₂、K₂O、Al₂O₃及低的CaO、MgO特征,A/CNK=1.17~1.25,属于强过铝质高钾钙碱性-钾玄质系列岩石。微量元素整体上富集Rb、Th、U、Zr、Hf,而Sr、Nb、Ti和P元素亏损,稀土元素配分模式表现为轻稀土元素富集右倾型,轻、重稀土元素分馏显著,Eu中等负异常(δEu值为0.44~0.73);Sr-Nd同位素特征显示,样品具有较高的Sr初始值(0.706 21~0.719 51),低的ε_Nd(t)值(-10.67~-9.72),其模式年龄为1.85~1.96 Ga,显示源区可能主要为古元古代的壳源物质。结合前人研究结果,认为研究区流纹岩是华南板块与印支地块后碰撞或碰撞晚期挤压热应力松弛的间隙环境下古老地壳变质泥岩部分熔融的产物。     

Lower crustal melting and the role of open-system processes in the genesis of syn-orogenic quartz diorite–granite–leucogranite associations: constraints from Sr–Nd–O isotopes from the Bandombaai Complex, Namibia

The Bandombaai Complex (southern Kaoko Belt, Namibia) consists of three main intrusive rock types including metaluminous hornblende- and sphene-bearing quartz diorites, allanite-bearing granodiorites and granites, and peraluminous garnet- and muscovite-bearing leucogranites. Intrusion of the quartz diorites is constrained by a U–Pb zircon age of 540±3 Ma.

Quartz diorites, granodiorites and granites display heterogeneous initial Nd- and O isotope compositions (_{Nd (540 Ma)}=−6.3 to −19.8; δ¹⁸O=9.0–11.6‰) but rather low and uniform initial Sr isotope compositions (⁸⁷Sr/⁸⁶Sr_initial=0.70794–0.70982). Two leucogranites and one aplite have higher initial ⁸⁷Sr/⁸⁶Sr ratios (0.70828–0.71559), but similar initial _Nd (−11.9 to −15.8) and oxygen isotope values (10.5–12.9‰). The geochemical and isotopic characteristics of the Bandombaai Complex are distinct from other granitoids of the Kaoko Belt and the Central Zone of the Damara orogen. Our study suggests that the quartz diorites of the Bandombaai Complex are generated by melting of heterogeneous mafic lower crust. Based on a comparison with results from amphibolite-dehydration melting experiments, a lower crustal garnet- and amphibole-bearing metabasalt, probably enriched in K₂O, is a likely source rock for the quartz diorites. The granodiorites/granites show low Rb/Sr (<0.6) ratios and are probably generated by partial melting of meta-igneous (intermediate) lower crustal sources by amphibole-dehydration melting. Most of the leucogranites display higher Rb/Sr ratios (>1) and are most likely generated by biotite-dehydration melting of heterogeneous felsic lower crust. All segments of the lower crust underwent partial melting during the Pan-African orogeny at a time (540 Ma) when the middle crust of the central Damara orogen also underwent high T, medium P regional metamorphism and melting. Geochemical and isotope data from the Bandombaai Complex suggest that the Pan-African orogeny in this part of the orogen was not a major crust-forming episode. Instead, even the most primitive rock types of the region, the quartz diorites, represent recycled lower crustal material.     

东天山巴里坤地区早石炭世高镁闪长岩的确定及地质意义

东天山巴里坤地区两个闪长岩体分别获得327 Ma 和333 Ma 的LA-ICP-MS 锆石U-Pb年龄,代表早石炭世一期岩浆活动。这些岩体具中等略高的SiO₂（51.33%～62.48%）、高MgO（2.04%～11.16%）、高TiO₂（0.67%～1.29%）、富钠（Na₂O/K₂O = 1.39～2.95）,相对富集LILE和LREE、贫HFSE,亏损Nb、富集Pb,具中等略高的轻重稀土分馏,无或弱负铕异常的右倾谱型,与赞岐质高镁闪长岩相同。岩体基本没有受到陆壳物质混染,其锆石ε_Hf（t）均为正值,且变化范围较大,指示来自受富集组分改造的亏损地幔。结合岩石中出现较多角闪石等含水矿物以及Pb富集,证明它们来自俯冲带之上有流体加入的地幔楔,高的TiO₂和中等略高的轻重稀土分馏进一步表明,是俯冲消减板片部分熔融的长英质熔体与地幔橄榄岩相互作用后,交代改造地幔熔融岩浆侵位的产物。结合区域同期弧火山岩和花岗岩类的形成,以及于晚石炭世-二叠纪广泛出现碰撞/后碰撞高钾花岗岩、A 型花岗岩以及镁铁质-超镁铁质岩体和基性岩脉的研究认为,博格达-哈尔里克构造带在早石炭世处于与大洋俯冲消减有关的岛弧环境,此后于晚石炭世晚期-早二叠世开始转入后碰撞伸展的构造环境。     

浙东白垩纪北漳和梁弄花岗岩体及其暗色岩石包体研究

浙东地区晚中生代花岗岩类在岩性上分为三类：花岗岩-二长花岗岩、钾长花岗岩和A型花岗岩。对后两类花岗岩已有较多研究,但对前一类,尤其是二长花岗岩的研究还较薄弱。选择浙东具代表性的北漳和梁弄二长花岗岩体及其所含暗色岩石包体,以及共生的石英闪长岩类,通过系统的岩石学与地球化学对比研究,提出浙东二长花岗岩属准铝质、高钾钙碱性Ⅰ型花岗岩类演化系列,暗色岩石包体是由花岗质岩浆在深部析离出的镁铁质微粒包体(MME),成分特征类似于石英闪长岩,说明三者具内在成因联系,均与俯冲作用关系密切。     

Pervasive assimilation of carbonate and silicate rocks in the Hortavær igneous complex, north-central Norway

The intrusive complex at Hortavær represents a magma transfer zone in which multiple pulses of gabbroic and dioritic magmas evolved along Fe- and alkali-enrichment trends. Extreme alkali enrichment resulted in nepheline-normative and sparse nepheline-bearing monzodioritic and monzonitic rocks. More evolved monzonitic and syenitic rocks are silica saturated and, in some cases, quartz bearing. Previous and current research recognized an abundance of clinopyroxene and other Ca-rich phases, such as scapolite, grossular-rich garnet, and igneous-textured calcite among the mafic and intermediate rocks. Even the most pyroxene-rich samples contain low Sc concentrations, which suggests early, intense fractionation of clinopyroxene. These features and the alkali enrichment are consistent with assimilation of carbonate-rich host rocks. Carbon isotope ratios of the igneous-textured calcite indicate an origin of the carbon from host rocks rich in calcite, consistent with assimilation. However, low _Nd values (−3.4 to −10.2) and moderate initial ⁸⁷Sr/⁸⁶Sr values (0.7052 to 0.7099) indicate the need for assimilation of quartzofeldspathic rocks as well. Models of combined assimilation and fractional crystallization indicate that assimilation of simple end members, either carbonate or silicate, cannot explain the entire data set. Instead, variable proportions of carbonate and silicate materials were assimilated, with the most pronounced assimilation effects in the mafic rocks. The reasons for variable degrees of assimilation are, as yet, uncertain. It is possible that assimilation of calc-silicate rocks with variable carbonate/silicate proportions resulted in the range of observed compositions. However, the importance of carbonate assimilation in mafic rocks compared to felsic ones suggests that assimilation of carbonates was predominant at high temperature and/or mafic magma compositions and assimilation of silicates was predominant at lower temperature and/or felsic magma compositions. We suggest that the ability of the mafic magma to dissolve higher proportions of carbonate contaminants is the result of the magma's ability to form clinopyroxene as a product of assimilation. In any case, extensive carbonate assimilation was possible because CO₂ escaped from the system.     

黑龙江黑河地区晚侏罗世岩浆弧的火成岩记录:与蒙古-鄂霍茨克洋关系探讨

黑龙江黑河北部的黑花山地区广泛发育中生代的侵入岩,但该侵入岩的形成时代、岩石组合、成因仍然不清.对黑花山地区侵入岩进行了野外、岩相学、岩石学、年代学、岩石地球化学等研究,以探讨该套岩石形成的时代、原因及大地构造背景.对两件二长花岗岩开展的LA-ICP-MS锆石U-Pb测年获得加权平均年龄分别为148.7±0.6 Ma、153.50±0.56 Ma,表明其形成于晚侏罗世.岩石组合主要为含有少量英云闪长岩（T₁）、奥长花岗岩（T₂）的T₁T₂G（狭义花岗岩）组合,即弧环境的侵入岩组合.上述岩石组合富硅、碱、高钾、过铝（A/CNK大于1）、低Fe₂O₃T.其在SiO₂-K₂O图上为高钾钙碱系列,硅镁图中为低铁钙碱（LF-LA）系列,Peacock指数为钙碱性或碱钙性,痕量元素蛛网图显示富集大离子亲石元素,亏损Nb、Ta、P、Ti、Y、Yb等元素.稀土元素配分模式为右倾型,轻稀土相对富集,（La/Yb）_n=13.78~29.85,无负Eu异常或弱正Eu异常或弱的Eu负异常.花岗岩类具有高Sr低Y的特征,Sr/Y比值介于29.53~103.80,具有“C型”埃达克岩的特征.上述岩石组合及其特征均指示了弧火成岩的性质,结合构造环境判别认为该区晚侏罗世花岗岩类形成于蒙古-鄂霍茨克洋的南向俯冲有关的环境,岩浆可能源于兴安弧加厚下地壳的部分熔融作用.      

新疆库鲁克塔格西段早泥盆世橄榄辉长岩年代学、地球化学特征及其地质意义

对新疆库鲁克塔格西段乌斯腾高勒东南橄榄辉长岩进行系统的锆石U-Pb年代学、全岩地球化学及Sr?Nd?Hf同位素研究,确定了岩石成因,并探讨其构造背景及地质意义。LA-ICP-MS锆石U-Pb年代学研究表明,橄榄辉长岩结晶年龄为410.3±5.7 Ma （MSWD = 0.56）,属早泥盆世岩浆活动的产物。全岩地球化学表明,岩石具有高Al₂O₃ 和CaO、贫碱、低P₂O₅和TiO₂的特征,属于低钾拉斑系列;岩石具有较高的Mg^#值（72.27～75.04）、明显的Eu正异常（δEu = 1.12～1.38）,其轻稀土元素轻微富集,重稀土元素相对平缓;微量元素蛛网图上岩石富集大离子亲石元素（如Rb、Ba、K、Sr）和Pb元素,亏损高场强元素（如Nb、Ta、P、Ti）。全岩Sr 同位素初始比值（⁸⁷Sr/⁸⁶Sr）_i值（0.703 663～0.704 013）相对较小,ε_Nd（t）值（-2.32～+4.98）变化范围较大,锆石ε_Hf（t）值为+7.8～+12.5。该岩体为俯冲板片流体改造过的相对较浅、对应于尖晶石二辉橄榄岩稳定区域的亏损地幔楔部分熔融,部分熔融比例在2%～10%之间,其母岩浆形成过程中遭受低程度的地壳物质混染,并经历了斜长石的堆晶作用和较弱的橄榄石和单斜辉石的结晶分异作用。结合区域已有地质资料,本文认为塔里木北缘库鲁克塔格地区在古生代中期经历了南天山洋南向俯冲过程,橄榄辉长岩产于主动大陆边缘环境,该时期大陆地壳生长方式为垂向生长,指示塔里木北缘具有增生造山带的属性。