华北克拉通五台绿岩带锆石年代学及地质意义

五台花岗-绿岩带位于华北克拉通中部造山带的中心地区,保存有较完整的地质记录,并赋存条带状铁建造(BIFs)型铁矿,一直是研究的热点地区之一。然而,该绿岩带尚需详细年代学研究来重新厘定其岩石地层划分。本文对该区域三个组,即金岗库组、柏枝岩组和鸿门岩组中发育的变质火山岩开展了锆石U-Pb年代学和Lu-Hf同位素组成分析。锆石U-Pb定年结果显示,五台花岗-绿岩带五台群中的金岗库组、柏枝岩组和鸿门岩组的变质火山岩喷发年龄分别为2540±8 Ma、2524~2530 Ma和2513~2517 Ma,同时还记录了~2700 Ma的继承年龄和1930~1853 Ma的变质年龄。锆石Lu-Hf同位素分析结果显示它们的εHf(t)值分别为+0.4~+5.5、+1.2~+7.5和+2.2~+10.5,相应的亏损地幔模式年龄为2639~2845 Ma、2546~2788 Ma和2425~2752 Ma,εHf(t)值呈现大的变化且增加的趋势。结合前人的研究,本文确定了五台群中的金刚库组、庄旺-文溪组、柏枝岩组和鸿门岩组分别形成于~2540 Ma、~2530 Ma、~2525 Ma和~2515 Ma,它们记录了四期火山活动,说明五台绿岩带中的表壳岩系尽管经历了变形变质作用的改造依然保存了较完整的地层层序序列,并提出回撤-前进式俯冲-底冲演化模型。这些结果对理解五台花岗-绿岩带乃至华北克拉通新太古代-古元古代构造及演化具有重要意义。

SHRIMP Zircon U-Pb Chronology and Geochemistry of the Henglingguan and Beiyu Granitoids in the Zhongtiao Mountains,Shanxi Province

Henglingguan and Beiyu metamorphic granitoids, distributed in the northwest of the Zhongtiaoshan Precambrian complex, comprise trondhjemites and calc-alkaline monzogranites, displaying intrusive contacts with the Archean Zhaizi TTG gneisses. And the Beiyu metamorphic granitoids consist mainly of trondhjemites, distributed at the core of the Hujiayu anticline fold. New SHRIMP zircon U-Pb dating data show that the weighted mean ^207pb/^206pb ages are 2435.9 Ma and 2477 Ma for the Henglingguan metamorphic calc-alkaline monzogranites and Beiyu metamorphic trondhjemites, respectively, and reveal -2600 Ma inherited core in magmatic zircons. Whole-rock geochemical data indicate that all the Henglingguan and Beiyu metamorphic trondhjemites and calc- alkaline monzogranites belong to the metaluminous medium- and high-potassium calc-alkaline series. These rocks are characterized by relatively high total alkali contents (Na2O+K2O, up to 9.08%), depleted Nb, Ta, P and Ti, and right-declined REE patterns with moderate to high LREEs/HREEs fractionation (the mean ratio of (La/Yb)n = 25). The Henglingguan and Beiyu metamorphic trondhjemites display negative Rb, Th and K anomalies in the multi-dement spider diagrams normalized by primitive mantle. Sm-Nd isotopic data reveal that these granitoids have initial εNd(t) =-1.2 to +2.4 and Nd depleted mantle model ages of TMD = 2622 Ma-2939 Ma. All these geochemical features indicate that these granitoids were formed in an continent-marginal arc, and the trondhjemites mainly originated from partial melting of juvenile basaltic materials and, howbeit, the Henglingguan metamorphic calc-alkaline monzogranites derived from recycling of materials in the ancient crust under a continent-marginal arc. The granitic magma underwent contamination and fractional crystallization during their formation.

Re-Os and U-Pb Geochronology of the Erlihe Pb-Zn Deposit,Qinling Orogenic Belt,Central China,and Constraints on Its Deposit Genesis

The Erlihe Pb-Zn deposit is an important mine of the Pb-Zn metallogenic zone in the South Qinling Orogen.It has been considered a sedimentary exhalative deposit in previous investigations because the ore body occurs concordantly at the transitional location of an upright fold.Re and Os isotopic analyses for paragenetic pyrites with sphalerite and galena from the ore body have been used to determine the timing of mineralization and to trace the source of metallogenic materials.The Re-Os isotopic data of four pyrite samples construct an isochron,yielding a weighted average age of 226±17 Ma（mean square weighted deviation=1.7）,which is considered the main mineralization age.A dioritic porphyrite vein sample,showing weaker mineralization,was also dated using the SHRIMP zircon UPb isotopic method to constrain the youngest metallogenic age of the ore deposit,because it distributes along a group of tensional joints cutting not only the upright fold in the deposit field,but also the main ore bodies.The dioritic porphyrite sample yields a weighted mean ^（206）Pb/^（238）U age of 221±3 Ma,which is slightly younger than the Re-Os isotopic isochron age of the pyrites,considered as the upper age limit of the mineralization,namely the ending age of the mineralization.The Os isotopic compositions of sulfide minerals distribute within a range between Os isotopic compositions of the crust and the mantle, indicating that the ore deposit can be derived from magma-related fluid,and the metallogenic materials are most likely derived from the mixing source of the crust and the mantle.The Erlihe Pb-Zn deposit and associated dioritic porphyrite vein,important records of Qinling tectonic-magmatism-mineralization activities,were formed during the Triassic collisional orogeny processes.

Petrogenesis of Indosinian Granitoids in Middle-Segment of South Qinling Tectonic Belt:Constraints from Sr-Nd Isotopic Systematics

South Qinling Tectonic Belt（SQTB）is located between the Shangzhou-Danfeng and Mianxian-Lueyang sutures.There are a lot of early Mesozoic granitoid plutons in its middle segment, comprising the Dongjiangkou-Zhashui granitoid plutons at the northeast,Huayang-Wulong-Laocheng granitoid plutons at the central part,Xiba granitoid pluton at the northwest and Guangtoushan-Liuba granitoid plutons at the southwest.These Indonisian granitoids contain a mass of various scale mafic enclaves,which show sometimes clear boundaries and sometimes transitional boundaries with their host granitoids.These granitoids also exhibit metaluminous to peraluminous series,commonly higher Mg# and a wide range of petrochemistry from low-K tholeiite series,through mid-K and high-K calc-alkaline series to shoshonite series and predominated samples are attributed to mid-K and high-K calc-alkaline series.Detailed analyses in Sr-Nd isotopic systematics and petrochemistry reveal that there may be regionally initial granitoid magma of the Indonisian granitoid plutons,comprising Dongjiangkou-Zhashui,Huayang-Wulong-Laocheng,Xiba,and Guangtoushan-Liuba granitoid plutons,which were produced by hybrids of magmas in various degrees,and the initial magmas were derived from both the mantle and the lower continental crust（LCC）sources in the SQTB.The initial granitoid magma further did the magma hybrid with the magmas from the LCC,crystallization fractionation,and assimilation with upper crustal materials during their emplacement to produce these granitoid plutons in the SQTB.These magmatism processes are most likely to occur under continent marginal arc and syn-collision to post-collision tectonic backgrounds.

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.

Ages of the Laocheng Granitoids and Crustal Growth in the South Qinling Tectonic Domain,Central China:Zircon U-Pb and Lu-Hf Isotopic Constraints

The Laocheng granitoid pluton is located in the South Qinling tectonic domain of the Qinling orogenic belt,southern Shaanxi Province,and consists chiefly of quartz diorite,granodiorite and monzogranite.A LA-ICP-MS zircon U-Pb isotopic dating,in conjunction with cathodoluminescence images,reveals that the quartz diorite and granodiorite were emplaced from 220 Ma to 216 Ma,while the monzogranite was emplaced at～210 Ma.In-situ zircon Hf isotopic analyses show that theε_（Hf）（t） values of the quartz diorite and granodiorite range from-8.1 to ＋1.3,and single-stage Hf model ages from 809 Ma to 1171 Ma,while theε_（Hf）（t）values of the monzogranite are-14.5 to ＋16.7 and single-stage Hf model ages from 189 Ma to 1424 Ma.These Hf isotopic features reveal that the quartz diorite, granodiorite and monzogranite were formed from the mixing of the magmas derived from partial melting of the depleted mantle and the lower continent crustal materials,and there were two stages of continental crust growth during the Neoproterozoic（～800 Ma）and Indosinian（～210 Ma）eras, respectively,in the south Qinling tectonic domain of the Qinling orogrnic belt,Central China.

Xiba Granitic Pluton in the Qinling Orogenic Belt, Central China: Its Petrogenesis and Tectonic Implications

Xiba granitic pluton is located in South Qinling tectonic domain of the Qinling orogenic belt and consists mainly of granodiorite and monzogranite with significant number of microgranular quartz dioritic enclaves. SHRIMP zircon U-Pb isotopic dating reveals that the quartz dioritic enclaves formed at 214±3 Ma, which is similar to the age of their host monzogranite （218±1 Ma）. The granitoids belong to high-K calc-alkaline series, and are characterized by enriched LILEs relative to HFSEs with negative Nb, Ta and Ti anomalies, and right-declined REE patterns with （La/Yb） N ratios ranging from 15.83 to 26.47 and δEu values from 0.78 to 1.22 （mean= 0.97）. Most of these samples from Xiba granitic pluton exhibit εNd（t） values of 8.79 to 5.38, depleted mantle Nd model ages （T DM ） between 1.1 Ga and 1.7 Ga, and initial Sr isotopic ratios （ 87 Sr/ 86 Sr） i from 0.7061 to 0.7082, indicating a possible Meso-to Paleoproterozoic lower crust source region, with exception of samples XB01-2-1 and XB10-1 displaying higher （ 87 Sr/ 86 Sr） i values of 0.779 and 0.735, respectively, which suggests a contamination of the upper crustal materials. Quartz dioritic enclaves are interpreted as the result of rapid crystallization fractionation during the parent magmatic emplacement, as evidenced by similar age, texture, geochemical, and Sr-Nd isotopic features with their host rocks. Characteristics of the petrological and geochemical data reveal that the parent magma of Xiba granitoids was produced by a magma mingling process. The upwelling asthenosphere caused a high heat flow and the mafic magma was underplated into the bottom of the lower continent crust, which caused the partial melting of the lower continent crustal materials. This geodynamic process generated the mixing parent magma between mafic magma from depleted mantle and felsic magma derived from the lower continent crust. Integrated petrogenesis and tectonic discrimination with regional tectonic evolution of the Qinling orogen, it is suggested that the granitoids are most likely products in a post-collision tectonic setting.

Geochemistry and Zircon U–Pb–Hf Isotopic Systematics of the Sanchahe Quartz Monzonite Intrusion in the North Qinling Tectonic Zone, Central China: Implications for its Petrogenesis and Tectonic Setting

The Sanchahe quartz monzonite intrusion is situated in the middle segment of the North Qinling tectonic belt, Central China mainland, and consists chiefly of sanukitoid–like and granodioritic-monzogranitic rocks. The sanukitoid–like rocks are characterized by quartz monzonites, which display higher Mg#（55.0–59.0）, and enrichments in Na2 O＋K2 O（7.28–8.94 %）, Ni（21-2312 ppm）, Cr（56-4167 ppm）, Sr（553-923 ppm）, Ba（912-1355 ppm） and LREE（（La/Yb）N =9.47–15.3）, from negative to slightly positive Eu anomalies（δEu=＋0.61 to ＋1.10）, but also depletion in Nb, Ta and Ti. The granodioritic-monzogranitic rocks diaplay various Mg#of 6.00-53.0, high Na2 O＋K2 O（7.20– 8.30%）, Sr（455–1081 ppm） and（La/Yb）N（27.6–47.8）, with positive Eu anomalies（δEu=1.03–1.57） and depleted Nb, Ta and Ti. Laser ablation inductively coupled plasma mass spectrometry（LA-ICPMS） zircon U-Pb isotopic dating reveals that the sanukitoid-like rocks were emplaced at two episodes of magmatism at 457±3 Ma and 431±2 Ma, respectively. The monzogranites were emplaced at 445±7Ma. Sanukitoid–like rocks have their εHf（t） values ranging from ＋0.3 to ＋15.1 with Hf–depleted mantle model ages of 445 to 1056 Ma, and the monzogranite shows its εHf（t） values ranging from 21.6 to ＋10.8 with Hf–depleted mantle model ages of 635 to 3183 Ma. Petrological, geochemical and zircon Lu –Hf isotopic features indicate that the magmatic precursor of sanukitoid–like rocks was derived from partial melting of the depleted mantle wedge materials that were metasomatized by fluids and melts related to subduction of oceanic slab, subsequently the sanukitoid magma ascended to crust level. This emplaced mantle magma caused partial melting of crustally metamorphosed sedimentary rocks, and mixing with the crustal magma, and suffered fractional crystallization, which lead to formations of quartz monzonites. However, the magmatic precursor of the granodioritic-monzogranitic rocks were derived from partial melting of subducted oceanic slab basalts. Integrated previous investigation for the adackitic rocks in the south of the intrusion, the Sanchahe intrusion signed that the North Qinling tectonic zone was developed in an early Paleozoic transitionally tectonic background from an island arc to back–arc.

Late Jurassic Cu-Mo Mineralization at the Zhashui-Shanyang District,South Qinling,China:Constraints from Re-Os Molybdenite and Laser Ablation-Inductively Coupled Plasma Mass Spectrometry U-Pb Zircon Dating

The Zhashui-Shanyang district is one of the most important sulfide deposits in the Qinling Orogen where the formation of porphyry-skarn Cu-Mo deposits has a close genetic link with the Yanshannian magmatism.Laser Ablation-Inductively Coupled Plasma Mass Spectrometry（LA-ICP-MS） U-Pb zircon dating of two granodiorite intrusions（Xiaohekou and Lengshuigou deposits）was investigated in the Zhashui-Shanyang district and the rock-forming ages obtained from 148.3±2.8 to 152.6±1.2 Ma,averaging 150.5 Ma,accompanied by a younger disturbance age of 144.3±1.7 Ma in the Lengshuigou intrusion,which is in excellent agreement with published sensitive high resolution ion micro-probe（SHRIMP）zircon date on the later monzodiorite porphyry phase in the Lenshuigou deposit.Two samples were selected for molybdenite ICP-MS Re-Os isotopic analyses from the Lengshuigou granodiorite porphyry,yielding Re-Os model ages from 149.2±2.7 Ma to 150.6±3.4 Ma, with a weighted mean age of 149.7±2.1 Ma.These mineralization ages overlap rock-forming ages of the host intrusions within the error range.This implies that the mineralization occurred in the Late Jurassic,which belongs to the tectonic phase B event of the Yanshan Movement,not Cretaceous as previously thought.Therefore,the Late Jurassic mineralization of the Zhashui-Shanyang district could be connected to the large-scale Yanshan molybdenum metallogenic period,the geodynamic regime of which is attributable to the far field response of convergence of surrounding plates,perhaps the approximately westward subduction of the Izanagi plate beneath the Eurasian continent.

华北克拉通恒山地区晚太古代变质火山岩的地球化学特征及构造意义

对恒山地区出露的变质火山岩开展岩相学、地球化学、锆石U-Pb年代学和Hf同位素研究,旨在确定其形成时代,探讨岩石成因及地球动力学意义。锆石U-Pb定年结果表明,这些变质火山岩喷发于新太古代晚期(2508±20 Ma)。地球化学分析结果显示,恒山变质火山岩由变质玄武岩和变质玄武安山岩组成,SiO_(2)(45.51%~62.67%)、FeO_(T)(4.43%~15.72%)和MgO(3.75%~8.14%)含量变化幅度大,是幔源岩浆经单斜辉石、角闪石和磁铁矿分离结晶的产物。这些变质火山岩富集轻稀土(LREE)和大离子亲石元素(LILE),亏损重稀土(HREE)和高场强元素(HFSE),具有相对高的Th含量和Th/Yb比值,呈现钙碱性岛弧火山岩的特征。结合不相容元素比值Nb/Yb,Zr/Yb和(Nb/La)_(N)的特点,推测其来源于俯冲带具流体交代特征的富集地幔源区。结合区域构造背景,推断恒山变质火山岩形成于新太古晚期大陆弧环境。

东天山大南湖-头苏泉岛弧带古生代侵入岩浆活动期次及基底性质

锆石U Pb定年结果显示:东天山大南湖头苏泉岛弧带中酸性侵入岩形成时代为古生代,处于465~265 Ma,可划分为4个期次。分别为:中奥陶世—晚志留世465~413 Ma、中—晚泥盆世391~377 Ma、石炭纪327~308 Ma,以及早—中二叠世284~269 Ma。锆石Hf同位素分析显示,锆石εHf(t)值为6.81~15.73,Hf同位素二阶段模式年龄为839~355 Ma,主要集中在598~429 Ma;465~413 Ma的侵入岩分布在卡拉塔格和大南湖,其εHf(t)值为11.34~15.20,相应的Hf同位素二阶段模式年龄为633~467 Ma;391~377 Ma的侵入岩分布于卡拉塔格,其εHf(t)值为6.81~13.32,相应的Hf同位素二阶段模式年龄为839~497 Ma;327~308 Ma的侵入岩分布在黄山西以及沁城南,其εHf(t)值为11.36~15.73,相应的Hf同位素二阶段模式年龄为575~429 Ma;284~269 Ma的侵入岩分布在土屋西和推克曼塔什,其εHf(t)值为8.94~14.51,相应的Hf同位素二阶段模式年龄是671~355 Ma。再结合前人的研究成果揭示,在大南湖头苏泉岛弧带底部可能存在老的地壳基底,并对这些岩浆活动有所贡献;该区古生代期间存在大约465 Ma早奥陶世以及330 Ma左右中石炭世2期地壳增生事件,并存在晚奥陶世—晚志留世、中—晚泥盆世和早—中二叠世三期地壳再造事件。

山西五台山滹沱群四集庄冰碛岩碎屑锆石年龄及其对大氧化事件研究意义

山西滹沱群四集庄组变质陆源碎屑混杂岩的砾石岩性复杂,分选和磨圆性差,砾石表面可见划痕和凹面,发育落石构造,表明其沉积于冰-水过渡带环境,记录了华北克拉通古元古代冰期事件。四集庄组不同层位不同岩石的碎屑锆石U-Pb年龄集中于2.5Ga左右,下部2件陆源碎屑混杂岩样品的碎屑锆石给出的最小年龄分别为(2 440±40)Ma和(2 400±23)Ma,而上部1件砂岩样品碎屑锆石的最小年龄为(2 121±22)Ma,说明冰川沉积作用发生在2.4Ga之后,2.1Ga之前或2.1Ga左右,与全球性休伦冰川事件(Huronian Glaciation Event,HGE)发生时间一致。砂岩相最小碎屑锆石年龄2.1Ga左右,说明五台地区冰川事件之后沉积作用仍未结束,冰川沉积发生在陆缘广海盆地。四集庄组之上的大石岭组具有碳酸盐岩碳同位素正漂移,沉积于2.12Ga之后,2.08Ga之前,与全球碳酸盐岩碳同位素正漂移事件时间一致。青石村组的红层沉积于2.08Ga左右,也与全球红层发育记录一致。华北克拉通滹沱群记录了相对完整的大氧化事件序列。

斑岩型铜、金、钼矿床成岩成矿特征差异的原因和意义

文中简要总结了斑岩型金矿、铜矿和钼矿在产出的构造环境,岩石地球化学特征和出溶流体的温度、压力、盐度、蚀变等方面的异同点,重点从元素的地球化学性质、岩浆的源区和过程(熔体和流体演化)3个方面解释了上述差异。Au、Cu和Mo在地球化学性质尤其是亲硫性上的差异决定了元素在不同的大地构造环境下的岩浆作用过程中的分布、迁移和富集特征,最终控制了矿床的分布。岩浆的源区及其温压条件、熔体上升过程中矿物的分离结晶和中上地壳岩浆房内的演化程度控制了成矿岩浆的地球化学特征,进而影响其就位时的压力和温度,从而导致出溶流体在p-T-X上的变化。结合岩浆岩中大离子亲石元素和SiO_2的含量,可以评估斑岩型矿床的类型:高的Rb含量是斑岩型钼矿的特征,高的Ba含量是斑岩型钼+铜矿的特征,高的Sr含量是斑岩型铜+金矿的特征。相对于俯冲环境,后俯冲环境下的成矿岩体具有更高的大离子亲石元素含量。矿区中酸性岩石的结构(斑状、似斑状、不等粒和等粒结构)可以用来初步指示成矿的潜力。

吕梁地区宁家湾岩体锆石U-Pb年代学、地球化学特征及地质意义

对呈小规模岩株状产出的宁家湾岩体进行野外地质、岩石学、岩石地球化学、锆石U-Pb同位素年代学和Hf同位素组成研究,目的是确定其岩石成因及地球动力学意义。两件样品的LA-ICP-MS锆石U-Pb定年结果分别为2364±6 Ma (MSWD=0.13)和2360±23 Ma (MSWD=4.0),属古元古代岩浆活动的产物。研究结果表明,宁家湾岩体富碱、高K和Si,具有高FeOT/MgO比值和高的高场强元素(HFSE)含量,富集Rb,Ba,Th和U等元素,具有低的Ca和Mg含量,明显亏损P和Ti,具弱轻重稀土分异和强Eu负异常(δEu=0.13～0.36)的海鸥型稀土分配模式,显示高分异I型花岗岩的特征。较高的Y/Nb值(1.2～2.8)、锆石的εHf(t)均为正值(+1.6～+6.4)以及单阶段模式年龄tDM1(Hf)和二阶段模式年龄tDM2(Hf)分别为2449～2629 Ma和2474～2711Ma的特点,表明源区可能为壳幔混合。明显的Nb,P和Ti负异常及Ce,Nd和Zr正异常,反映出大陆边缘弧岩浆岩的特征。结合区域地质背景,认为宁家湾岩体很可能形成于岛弧构造环境。

山西五台绿岩带柏枝岩组条带状铁建造(BIFs)成因及其环境意义

五台绿岩带BIFs主要分布在金岗库组、文溪组和柏枝岩组中,其中以柏枝岩组BIFs铁矿最具工业规模和开采价值。对柏枝岩组8个BIFs矿区及出露点的12件铁矿石和1件变质火山岩样品进行了岩相学、地质年代学和地球化学分析。研究表明,柏枝岩组BIFs自东向西含铁矿物由磁铁矿逐渐转变为碳酸铁矿物(铁白云石或菱铁矿),对应的CaO含量和FeO/Fe_(2)O_(3)值有明显增加的趋势。LAICPMS锆石UPb定年结果显示,BIFs赋存的变质火山岩(石英绿泥钠长片岩)原岩形成于(2526±14)Ma,代表了柏枝岩组BIFs的沉积年龄。高Al_(2)O_(3)、TiO_(2)、HFSE和TREY含量及其之间呈正相关性暗示BIFs中有微量陆源碎屑物质混染,并且根据La/Sc,Th/Sc和Zr/Sc值认为这些物质主要来源于地壳长英质碎屑。尽管如此,大部分BIFs显示出一致的La正异常、Y正异常、LREE亏损、HREE富集及高于球粒陨石的Y/Ho值的特征,与现代海水REY特征相一致。并且BIFs还显示出强烈的正Eu异常,表明有高温热液流体的参与。根据改进的Sm/Yb vs.Y/Ho和Eu/Sm vs.Sm/Yb元素混合计算模型可知,柏枝岩组BIFs的成矿物质来源于大量海水和少量海底高温热液(0.1%~1%)的混合,并在沉积过程中混入少量地壳长英质碎屑组分(<0.1%)。相比西部富碳酸盐BIFs,东部和中部富磁铁矿BIFs受到地壳长英质碎屑的贡献比例更大。此外,根据五台绿岩带新太古代—古元古代“二阶段”构造演化模型,柏枝岩组BIFs形成于第一阶段的末期。并且,依据无Ce异常、正Eu异常、较低的Th/U值和极高的Fe/Mn值,认为沉积时水体整体处于缺氧状态,但其水体是不均一的,出现了细微的氧化还原分层。西部富碳酸盐BIFs因沉积于深部的还原水体中而具有更高的正Eu异常,而中部和东部富磁铁矿BIFs沉积于相对较浅的弱还原水体中而具有较低的Eu异常。

白细胞介素-33及其受体基质裂解素2信号通路在哮喘小鼠气道中的作用机制研究

目的探讨白细胞介素(IL)-33及其受体基质裂解素2(ST2)信号通路在哮喘小鼠气道中的表达、激活及其相关机制。方法将36只小鼠随机分为正常对照组12只、哮喘未干预组12只和u0126干预组12只。建立卵清蛋白(OVA)致敏的小鼠哮喘模型。收集支气管肺泡灌洗液(BALF),并对炎症细胞进行分类和计数。用酶联免疫吸附试验(ELISA)法检测BALF中IL-33和ST-2的水平。苏木精-伊红(HE)染色光镜下观察肺组织的病理变化。结果哮喘未干预组BALF中IL-33、ST2水平高于正常对照组(P<0.05),u0126干预组低于未干预组(P<0.05)。与正常对照组相比,未干预组小鼠肺组织病理学损伤及气道重塑明显加重,而u0126干预组小鼠肺组织病理学损伤及气道重塑较干预组缓解。结论IL-33/ST2信号通路参与哮喘小鼠气道炎症与气道重塑的分子机制。

Evaluating the Provenance of Metasedimentary Rocks of the Jiangxian Group from the Zhongtiao Mountain Using Whole-Rock Geochemistry and Detrital Zircon Hf Isotope

In this study, whole-rock geochemical and Nd isotopic data, as well as detrital zircon Hf isotopes of Palaeoproterozoic metasedimentary rocks from the Jiangxian Group are presented to evaluate the characteristics of their provenance and the tectonic history. The major and trace element compositions are comparable to Post-Archean upper continental crust （PA-UCC）, but have slight enrichment in the LILE, with the exception of Cs and Sr, and a slight depletion in ferromagnesian elements, HFS elements, such as Nb and Ta, and some major elements, such as CaP and Na2O. The geochemical data reveal that the collected metasedimentary rocks have experienced intermediate source weathering with chemical index of alteration values ranging from 72 to 78, varying degrees of K- metasomatism, and post-depositional loss of Na, as well as negligible sorting, and are derived from the weathering of mostly felsic and non-mafic rocks. The selected Lu-Hf isotopic analysis on detrital zircon points to both the Trans-North China Orogen and Eastern Block of the north China craton as the most likely sources for the metasedimentary rocks of the Jiangxian Group. However, a contribution of detritus from the Western Block of the north China craton can be ruled out. The sediments were probably deposited in a back-arc basin within an active continental margin setting.

吕梁地区近周营组蚀变火山岩U-Pb-Hf同位素特征及其地质意义

选择吕梁群中原岔上群北部地层的蚀变火山岩进行锆石U-Pb年代学和Hf同位素研究。锆石U-Pb测试获得两组年龄结果,较年轻的谐和年龄为1813±6 Ma (n=7),较老的207Pb/206Pb加权平均年龄为2516±31 Ma(n=2),前者为火山岩喷发时代,后者代表捕获锆石年龄。年轻锆石的εHf(t)值为-10.8^-2.3,TDM1值为2308~2655 Ma;捕获锆石的εHf(t)值为+10.0^+13.1。年龄约为2.5 Ga锆石的εHf(t)值高于亏损地幔演化线,考虑到UPb同位素和Hf同位素测点位置不完全相同,说明所获得的Hf同位素组成为无地质意义的混合数值;年龄约为1.8 Ga锆石的Hf同位素特征反映其可能源于富集地幔或受地壳物质混染的亏损地幔。结合前人的研究成果,推断岩浆作用事件发生在约1.81 Ga的碰撞后阶段。

Petrogenesis of the Paleoproterozoic Guandishan Granitoids in Shanxi Province:Constraints from Geochemistry and Nd Isotopes

The Guandishan granitoids consist mainly of various granitoid intrusions with different scales, including the Huijiazhuang intrusion, Shizhuang intrusion and Hengjian intrusion, which were formed between 1906 Ma and 1848 Ma. On the basis of geological and petrological characteristics, these granitoids can be classified into two groups： the earlier gneissic granodiorites and monzogranites, and the later massive leuco-monzogranites. Their geochemical and Nd isotopic features indicate that they could be derived from complicated partial melting of supracrustal rocks with an affinity of continental arc materials, such as sandy shale and pelite, and with garnet, pyroxene, hornblende and plagioclase as residual phases. Biotite, feldspar and other minerals were most likely fractionated during the magma evolution. Their source may have an affinity with continental arcs, and the granitoids could be derived from the main syn-collisional to late-orogenic tectonic environment, which may be related to the final amalgamation between the Eastern and Western continental blocks in the North China Craton.

Indosinian Tectonic Setting of the Southern Yidun Arc: Constraints from SHRIMP Zircon Chronology and Geochemistry of Dioritic Porphyries and Granites

A mass of granitoid and dioritic intrusions are distributed in the southern Yidun Arc, among which the representative Indosinian intrusions include the Dongco and Maxionggou granitoid intrusions in Daocheng County and hypabyssal intrusions intruding into arc volcanic rocks near the Xiangcheng town. The Dongco and Maxionggou granitoid intrusions consist mainly of porphyraceous monzogranites, megacryst monzogranites and aplite granites. The Xiangcheng hypabyssal intrusions are composed dominantly of dioritic porphyries. SHRIMP zircon ages of 224±3 Ma and 222±3 Ma have been obtained for the Dongco granitoid intrusion and the Xiangcheng dioritic porphyries, respectively. The Xiongcheng dioritic porphyries show a calc-alkaline geochemical feature, and are characterized by higher Sr/Y ratios, depletive Nb, Ta, P and Ti, enriched LILEs, and lower εNd （t） （=-3.27）, suggesting that they might be derived from mantle source magmas that were obviously contaminated by continent crustal materials. However, the Dongco and Maxionggou granitoids belong to high-potassium calcalkaline series with a per-metaluminous feature, and are characterized by higher CaO/（∑FeO＋MgO） and Al2O3/（∑FeO＋ MgO） ratios, lower （La/Yb）n and Sr/Y ratios, depletive Nb, Ta, Sr, P and Ti, enriched LILEs, and very low εNd （t） （=-8.10）, indicating that the granitoids might be derived from partial melting of continental crust materials mainly of graywacke. Petrogenesis of Dongco and Maxionggou granitoids implies that there was an oceanic crust between the Zongza continental block （ZCB） and western margin of the Yangtze Craton （WMYZC）. And the oceanic crust slab subducted westward during the Indosinian Epoch, producing an Andes-type continent marginal arc and a backarc basin at the WMSCC. Then the oceanic basin closed and a sinistrally lateral collision occurred at ca. 224 Ma-222 Ma between the ZCB and the WMYZC, causing partial melting of sediments in the back-arc basin to generate granitoid magmas of the Dongco and Maxionggou intrusions.