山东胶南威海造山带荣成岩套花岗质片麻岩的形成时代——锆石SHRIMP U-Pb定年

胶南-威海造山带荣成岩套花岗质片麻岩由闪长质片麻岩-石英闪长质片麻岩-英云闪长质片麻-一奥长花岗质片麻岩-花岗闪长质片麻岩-黑云二长花岗质片麻岩-二长花岗质片麻岩类组成,早期为TTG质花岗岩,晚期为二长花岗岩类。自早到晚存在明显的富钾演化特征。根据新的SHRIMPU-Pb锆石定年结果,该岩套早期闪长质片麻岩年龄为（741±10）Ma,英云闪长质片麻岩年龄为780-760Ma。晚期二长花岗质片麻岩年龄为760-714Ma。所以,可把荣成岩套花岗岩时代限定在800-700Ma之间（南华纪）,其形成与华北克拉通岩石圈减薄有关。     

鲁东地区侵入岩形成时代和期次划分

鲁东地区前寒武纪侵入岩其侵入活动集中于新太古代和新元古代,均遭受不同程度的区域变质和韧性剪切带的改造,形成一套花岗质片麻岩类。新太古代早期TTG质花岗岩分布于胶北隆起区莱州一栖霞一带,经受了区域变质作用,形成一套灰色片麻岩,锆石内核SHRIMPU—Pb年龄2726—2707Ma基本代表岩浆结晶年龄,锆石变质边为2500Ma;古元古代侵入岩——莱州基性一超基性岩组合形成于1900～1850Ma左右,锆石SHRIMPU—Pb年龄（1852±9）Ma,（1868±11）Ma;新元古代侵入岩主要为花岗闪长质-二长花岗质片麻岩,出露于胶南-威海造山带,锆石U～Pb定年结果集中为892～605Ma,其中荣成超单元锆石SHRIMPU—Pb年龄720～780Ma。中生代侵入岩以花岗岩类为主,集中出露于半岛北部和东南沿海一带。燕山早期侵入岩文登超单元、垛崮山超单元、玲珑超单元锆石SHRIMPU—Pb同位素年龄值集中在167～150Ma;燕山晚期侵入岩大店超单元锆石SHRIMPU～Pb年龄120±4Ma,崂山超单元锆石SHRIMPU～Pb同位素年龄值为（120±2）～（114±2）Ma。     

Petrogenesis of Paleoproterozoic diorite porphyries in Luojiazhuang,western Shandong:constraints from LA-ICP-MS zircon U-Pb geochronology and geochemistry

Based on the study of LA-ICP-MS zircon U-Pb geochronology and whole-rock geochemistry for the Luojiazhuang diorite porphyries in Menying,western Shandong,the analyzed zircons exhibit oscillatory growth zoning in the cathodoluminescence images and have high Th / U ratios( 0. 15--1. 53),indicating a magmatic origin. In addition,most of the zircons have narrow metamorphic edges,suggesting that late metamorphic events may exist. The youngest group of magmatic zircon207 Pb /206 Pb ages ranging from 2 384 Ma to 2234 Ma,yielding a weighted mean age of 2353 ± 14 Ma,which represents the forming age of the diorite porphyries,as the Early Paleoproterozoic. Geochemically,the samples are characterized by low SiO_2( 54. 54% and 55. 47%),high MgO( 5. 22% and 5. 49%) and Mg~#values( 58 and 59). Moreover,they show enrichment of light rare earth elements and large ion lithophile elements( Rb,Ba and K),depletion of heavy rare earth elements and high field strength elements( Nb,Ta,Zr and Hf),positive anomaly of Pb,and negative anomaly of Ti. The fact implies that the Luojiazhuang diorite porphyries might derive from partial melting of enriched lithospheric mantle and mixed with an amount of continental crust material. In summary,they may form in the compression tectonic setting that stretching along the east-west direction at the North China Craton in the Early Paleoproterozoic.     

新疆阿尔泰别也萨麻斯稀有金属矿床含矿伟晶岩与花岗岩围岩成因关系

别也萨麻斯矿床是目前新发现的分布在新疆北阿尔泰以Li矿化为主的花岗伟晶岩型稀有金属矿床,具有独特性和代表性。矿区发育Li-Nb-Ta矿化和Nb-Ta矿化两类伟晶岩,二云母二长花岗岩是含矿伟晶岩脉群的直接围岩。在系统的野外地质特征调查(包括野外露头和钻孔岩芯赋矿岩系、矿化特征、蚀变类型等的详细观察)基础上,对含矿伟晶岩和二云母二长花岗岩开展了LA-ICP-MS锆石U-Pb定年和原位Hf同位素研究。获得锆石206Pb/238U加权平均年龄分别为(151.0±1.8)Ma和(449.0±4.2)Ma,含矿伟晶岩形成于晚侏罗世,二云母二长花岗岩则形成于晚奥陶世。含矿伟晶岩和二云母二长花岗岩的εHf(t)值分别为0.62~1.30和1.35~6.07,二阶段Hf模式年龄为1161~1118 Ma和1345~1037 Ma。含矿伟晶岩的εHf(t)值较花岗岩小得多,二阶段Hf模式年龄与形成年龄的差值较花岗岩大得多,表明两者是阿尔泰造山带在不同演化阶段下的产物。悬殊的年龄差、不同的大地构造背景与不同的形成物源表明别也萨麻斯稀有金属矿床含矿伟晶岩与二云母二长花岗岩在成因上并无联系,近矿花岗岩围岩并非含矿伟晶岩脉的真正母体。     

Characteristics and tectonic setting of volcanic rocks in Early Cretaceous Baiyingaolao Formation of Keyouzhongqi area，Inner Mongolia

The authors studied zircon LA-ICP-MS U-Pb dating,the zircon Hf isotope and geochemistry of acidic volcanic rocks in Baiyingaolao Formation of Keyouzhongqi area,Inner Mongolia,and discussed the chronology, source region and tectonic setting of the volcanic rocks in the studied area． The clear oscillatory zoning of zir- cons indicates a typical magmatic origin,and the results of dating show that the volcanic rocks of Baiyingaolao Formation were formed in Early Cretaceous (121.5 ±1.0 Ma)． The features of major and trace elements show that the rocks are alkali-rich,poor in calcium and magnesium with enrichment in LILEs like Th,U,K and Gd and depletion in HFSEs,e.g. Nb,Ta,Sr and Ti． The fact implies that they were the products of partial melting of the crust． εHf(t) = ( +6.30--+9.06) and TDM2=600--835 Ma,suggest the magma originated from par- tial melting of the young crust． Combined with the evolution of regional tectonic structure,the authors conclude that the acidic volcanic rocks of Baiyingaolao Formation may be formed under the extensional environment relat- ed to the subduction of Paleo-Pacific Plate．     

Petrogenesis and tectonic setting of granite porphyry in Keyouzhongqi area,Inner Mongolia

The authors studied the geochemistry,zircon U-Pb ages,Hf isotope of the granite porphyry and its petrogenesis and tectonic setting in the studied area． The zircon U-Pb dating indicates the formation of the gran- ite porphyry is in Early Cretaceous (125． 1 ±1． 5 Ma)． The granite porphyry has high-SiO2and alkali-rich fea- tures,which belongs to high-K calc-alkaline series rocks (A/CNK = 0． 95%--1． 25%)． The analyses of trace elements show the characteristics of a swallow-shaped ＲEE distribution pattern with enrichment in LＲEEs and most of LILEs and HFSEs,depletion in Ba,Sr,Nb,P and Ti,and especially strong depletion in Eu,which indicates the granite porphyry belongs to the aluminous A-type granite． Their εHf(t)range from 5． 94 to 8． 80 with Hf two-stage model ages (TDM2) of 620 Ma to 803 Ma． Combining with the regional tectonic background, we conclude that the source of the rocks is the new crust materials accreted from depleted mantle in Neoprotero- zoic and is the product of partial melting of middle and lower crustal rocks,which may be suffered from the dual impact of the subduction of the Palaeo-Pacific Ocean and the closure of the Mongol-Okhotsk Ocean．     

Zircon U-Pb geochronology and geochemistry of Early Cretaceous granodiorite porphyries in Hutouya,western Shandong and their implications for petrogenesis

Zircon LA-ICP-MS U-Pb age and whole-rock geochemistry data are presented for the Hutouya granodiorite porphyries in Mengyin,western Shandong,to restrict its petrogenesis.The analyzed zircons exhibit oscillatory growth zoning and core-rim textures in the cathodoluminescence images and have high Th/U ratios( 0.04--1.66),indicating its magmatic origin.The youngest group of magmatic zircon yields weighted mean~(206)Pb/~(238) U age of 132 ± 2 Ma,which represents the forming age of the granodiorite porphyries,i.e.,the Early Cretaceous.The oldest group of magmatic zircon~(207)Pb/~(206) Pb ages ranges from 2 398 Ma to 2 370 Ma,yielding a weighted mean age of 2 389 ± 23 Ma,suggesting that the basement of the North China Craton should exist in the research area.Geochemically,the samples are characterized by high Si O_2( 70.38% and 64.87%),low Mg O( 0.60% and 1.53%) and Mg~#values( 42.92 and 50.42).Moreover,they show enrichment of light rare earth elements and large ion lithophile elements( e.g.Rb,Ba and K),depletion of heavy rare earth elements and high field strength elements( e.g.Nb and Ta),positive anomaly of Pb,and negative anomaly of Ti.These results,together with previously published data,indicate that the Hutouya granodiorite porphyries were derived from partial melting of a delaminated lower continental crust and subsequent interaction with the mantle peridotites.They are consistent with the period of lithospheric thinning beneath the eastern North China Craton and may be formed in an extensional tectonic environment.     

山东崂山花岗岩形成时代——锆石SHRIMP U-Pb定年

白垩纪崂山超单元花岗岩由二长花岗岩、正长花岗岩、碱长花岗岩类组成,自早到晚存在明显的富钾演化特征。根据新的SHRIMP U-Pb锆石定年结果,该超单元早期相浮山亚超单元的浮山二长花岗岩年龄为(120±2)Ma,晚期相崂顶亚超单元的崂山碱长花岗岩年龄为(114±2)Ma。所以,可把崂山超单元花岗岩时代限定在110~120 Ma之间(早白垩世),其形成与华北克拉通岩石圈减薄有关。     

新疆卡拉麦里姜巴斯套组火山岩地球化学特征与构造意义

通过对新疆卡拉麦里姜巴斯套组火山岩野外地质特征、岩石学和高精度同位素年代学的研究,发现姜巴斯套组火山岩具典型双峰式组合,岩石类型包括玄武岩-酸性火山碎屑岩-玄武粗面安山岩;得到玄武粗面安山岩LA-ICP-MS锆石U-Pb年龄为(319.8±2)Ma(加权均方偏差值为3),表明姜巴斯套组火山岩形成于早石炭世谢尔普霍夫阶。对火山岩地球化学特征的研究表明,姜巴斯套组火山岩钙碱性系列、高钾钙碱性系列和钾玄岩系列岩石兼而有之,岩石的稀土元素配分曲线均为轻稀土元素富集型,无明显Eu异常,玄武岩和玄武粗面安山岩具有K正异常和Sr负异常,酸性火山碎屑岩表现出Nb、Ta和Ti显著亏损。总体来说,姜巴斯套组火山岩富集大离子亲石元素,相对亏损高场强元素。玄武岩和玄武粗面安山岩表现出大陆裂谷(大陆板内拉张区域)岩石特征;酸性火山碎屑岩表现出岛弧或者活动大陆边缘岩石属性。总之,姜巴斯套组火山岩形成于卡拉麦里洋盆闭合碰撞造山后的拉张伸展环境,卡拉麦里地区在早石炭世末期就进入了碰撞后的陆内伸展拉伸阶段。     

U-Pb geochronology,geochemistry and tectonic implications ofdiorite from Nangnimsan of Mehe in northern Da Hinggan Mountains

LA-ICP-MS zircon U-Pb dating indicates that the weighted average age of diorite from Nangnimsan,Mohe in the northern Da Hinggan Mountains in Heilongjiang Province is 516.2±1.7 Ma,as a result of magmatic intrusion of Early Cambrian. Geochemistry analysis indicates that the rocks belong to high-K calc-alkaline series,with low content of SiO_2( 52.24%-53.64%) and high Mg( MgO = 5.67%-6.56%,Mg~#= 61. 05-65. 46).The rocks are characterized by the enrichment of LREE and LILE( e.g. Rb,Ba,Pb),and relative depletion in HREE and HFSE( e.g. Ta,Nb,P,Ti),and with a high content of Sr( 442. 3-622. 3) × 10~(-6),Yb( 2.49-3.42) ×10~(-6) and Y( 25.64-35.49) ×10~(-6),and slightly negative Eu anormaly( δEu= 0.60-0.81). Based on Rb/Sr( 0.15-0.25) and Rb/Nb( 8.27-15.12),it is concluded that the primary magma of diorite was derived from the mixture of the crust and mantle. Combined with background of regional tectonic evolution,it is suggested that diorite was formed in the extensional environment after the collage of the EGM with the Siberian.     

Geochemistry,U-Pb,Hf isotopic characteristics and geological significance of Zhalaxiageyong trachydacite in Tuotuohe area,Qinghai

The Zhalaxiageyong lead-zinc-copper polymetallic deposit is a typical porphyry deposit of the Tuotuohe area. Whole-rock geochemical analyses,Zircon U-Pb dating and Hf isotope analysis are undertaken for the ore host trachydacite with the aim of constraining its petrogenesis,magma source and regional tectonic setting.LA-ICP-MS zircon U-Pb dating indicates that the trachydacite was formed in 32. 68 ± 0. 50 Ma( MSWD =1. 6),i. e.,Oligocene. The trachydacite is rich in potassium and poor in Mg#( 5. 10-9. 70),belonging to the peraluminous shoshonite series. The rocks are enriched in LILE( large ion lithophile elements) Rb,Ba,K and LREE,depleted in HFSE( high field strength elements) Nb,Ta,P,Ti,with high Sr and low Y and Yb,having the characteristics of the C type adakite. It is calculated that the initial εHf( t) of the zircons range from-0. 92 to 2. 07 and their two-stage Hf model ages T_(DM2) range from 978 Ma to 1 169 Ma. The magma source should be mainly the partially melt mafic rocks of the thickened Middle Neoproterozoic lower crust of the Northern Qiangtang massif with the addition of ancient aluminosilica material in the melting process. The rocks formed in the tectonic setting of delamination of lithosphere and extension of the thickened crust. During the period of 40-32 Ma,large-scale potassium rich alkaline magmatism occurred in this area. The porphyry metallogenesis is related to the magmatic activities in this period.     

Zircon U-Pb age,geochemical and Nd isotopic data of Middle Jurassic high-Mg dioritic dike in Liaodong Peninsula,NE China

Zircon LA-ICP-MS U-Pb age, geochemical and Nd isotopic data are presented for a newly recognized high-Mg dioritic dike from Haicheng, Liaodong Peninsula, NE China, to constrain its petrogenesis. The zircons from the high-Mg diorite exhibit striped absorption and oscillatory growth zoning in the cathodoluminescence （CL） images, and have high Th/U ratios （0. 05-0.9）, indicating a magma origin. Zircon LA-ICP-MS U-Pb dating indicates that 206pb/238U ages of 12 spots of zircons are between 167 Ma and 178 Ma, yielding a weighted mean 206pb/238U age of 172 ＋ 2 Ma （MSWD =4. 1 ）, which represents the forming age of the high-Mg dioritic dike, i. e. Middle Jurassic. Geochemically, the samples have SiO2 =55.4-60. 6 wt. % , Na20 =2. 2-2.76 wt. % , K20 = 1.32-2. 02 wt. % and （Na2O ＋ K2O） =3.82--4. 47 wt. %, belonging to sub-alkaline series and displaying a calc-alkaline evolutionary trend. They are characterized by high MgO （4. 75-6.85 wt. % ）, Mg# （55-61）, Cr（130-262 ppm）, Ni（63-130 ppm）, Sr（568-857 ppm）, and Ba（484-1 130 ppm） contents, with geochemical features analogous to those of high-Mg adakites. They show variable end （t） values （ - 1.3 to - 3.9） , with a weighted value of - 2. 7, which plot intermediately between the field of the ancient continental crust and the depleted mantle source, indicating that both the lower crust and mantle source are necessary for the generation of the parent magma of the Haicheng high-Mg diorites. The Haicheng high-Mg dioritic dike in the Liaodong Peninsula and the Jurassic magmatism in the eastern North China Craton formed under a continental crustal thickening setting that may be related to subduction of the Paleo-Pacific oceanic plate.     

鲁西地区石门山—凤仙山岩体的锆石SHRIMP U-Pb定年及形成时代

鲁西地区石门山岩体主要岩性为片麻状花岗闪长岩,原划为新太古代早期侵入岩。根据新测锆石SHRIMPU-Pb年龄为(2530±8)Ma,其形成时代确定为新太古代晚期。凤仙山岩体为中粒二长花岗岩,锆石SHRIMP U-Pb年龄为(2513±12)Ma,并侵入片麻状花岗闪长岩。石门山岩体属峄山岩套,为TTG质花岗岩,是地幔岩浆侵入混入地壳物质形成的。凤仙山岩体属傲徕山岩套二长花岗岩,为上地壳物质重熔(深熔)作用形成的。峄山岩套TTG类岩石是2560~2530 Ma壳幔岩浆活动的产物,岩体普遍具有片麻状构造,表明经历变质变形作用。未受区域变质作用的傲徕山岩套大规模壳源花岗岩是2530~2500 Ma地壳物质部分熔融形成的,与华北克拉通新太古代末超大陆拼合有关,2530 Ma是鲁西地区重要的构造热事件发生时期。     

新疆且末阿尔金断裂南缘斜长片麻岩锆石U-Pb测年及其地质意义

在阿尔金地块南缘构造混杂岩带中,新发现了多个规模较大的斜长片麻岩块体。运用LA-ICP-MS锆石U-Pb定年分析方法,对阿尔金地块南缘且末大石门地区构造混杂岩带中的斜长片麻岩进行了年代学测定,并初步探讨其地质意义。30个锆石颗粒的28个有效测点,测出的年龄明显分为2个区间:①(1784±41)^(2150±34)Ma之间,加权平均值为(2130±27)Ma(MSWD=0.21,1σ);②(2324±32)^(2684±51)Ma之间,加权平均值为(2520±23)Ma(MSWD=0.06,1σ)。根据该次年龄测试结果和区域调查资料表明,阿尔金地块南缘且末大石门地区,在古元古代存在一期构造-热事件,该期事件与吕梁运动的时限相吻合。     

鄂东南付家山矽卡岩型(Cu-)W矿床成岩成矿时代及地质意义

付家山（Cu-）W矿床是鄂东南地区新近发现的大型矽卡岩型矿床之一,成矿与花岗闪长斑岩关系密切。为了精确获得该矿床成岩成矿年龄,利用LA-ICP-MS锆石U-Pb和辉钼矿Re-Os同位素定年法对其进行了系统的成岩成矿年代学研究,并基于长江中下游成矿带晚中生代沉积地层及构造变形、地球物理和岩石地球化学等证据探讨了其成岩成矿构造背景。结果显示:花岗闪长斑岩锆石U-Pb加权平均年龄为（144±3）Ma,而辉钼矿Re-Os模式年龄为（146±2）Ma,成岩与成矿作用均形成于晚侏罗世-早白垩世。付家山（Cu-）W矿床形成时代与长江中下游地区大规模岩浆成矿事件时间一致,包括鄂东南地区在内的长江中下游地区的构造演化历史及最新的年代学数据表明,付家山（Cu-）W矿床极有可能形成于岩石圈伸展减薄构造背景。付家山等晚侏罗世-早白垩世矽卡岩型（Cu-）W矿床的发现及厘定指示了鄂东南矿集区具有良好的钨矿找矿前景。      

Zircon U-Pb geochronology and Hf isotopic constraints on petrogenesis of Carnian Huanglonggou granodiorites in Wulonggou area of Eastern Kunlun Orogen,NW China

The Wulonggou area located in the Eastern Kunlun Orogen in NW China is characterized by extensive granitoid magmatism,ductile faulting and orogenic gold mineralization.The Huanglonggou granodiorite is cut by an orogenic gold-bearing fault.This study investigated the major and trace-element compositions,zircon U-Pb dates and zircon Hf isotopic compositions of the Huanglonggou granodiorite.One Huanglonggou granodiorite sample yielded a weighted mean U-Pb zircon age of~221 Ma(Carnian).The Carnian granodiorite is metaluminous,with high alkalis contents of 6.37%--8.86%,high Al_2O_3contents of 15.41%--16.19%,high Sr contents of(426--475)×10~(-6),relatively high Sr/Y ratios,high(La/Yb)_Nvalues and low HREE,suggesting an adakite type high-Si O_2granite.The Huanglonggou granodiorite sample has zirconε_(Hf)(t)values ranging from-4.4 to+1.1.These Hf isotopic data suggest that the Carnian granodiorite was likely derived from the partial melting of subducted Paleo-Tethys oceanic slab.It is suggested that the Late Triassic granodiorite was emplaced during the northward subduction of Paleo-Tethys oceanic slab.Orogenic gold mineralization in the Wulonggou area formed after the emplacement of the Late Triassic intrusive rocks.     

即墨地区莱阳群底部止凤庄组地质特征及其碎屑锆石LA-ICP-MS U-Pb年龄地质意义

为了了解盆地沉积初期的物源特征,对位于胶莱盆地东缘即墨地区早白垩世莱阳群止凤庄组沉积特征、物质组成及碎屑锆石进行了U-Pb同位素测年研究。野外调查表明,止凤庄组为一套陆源碎屑沉积,具有近源沉积的特点。南泊一带止凤庄组底部碎屑岩碎屑锆石LA-ICP-MS U-Pb年龄介于233~734 Ma,年龄分布于5个区间,呈现明显的幕式特征,至少记录了2次重要的构造热事件。侵入于止凤庄组石英二长岩的锆石U-Pb加权平均年龄为(123.50±0.95)Ma,限定了止凤庄组地层沉积上限年龄为123.50 Ma。综合分析认为,止凤庄组物源主要来自苏鲁造山带,部分来自扬子板块。这有助于了解胶莱盆地沉积初期其物源区苏鲁造山带的地体情况。     

江西赣州隆木花岗岩体年龄、成分特征及其构造意义

为了查明江西赣州隆木花岗岩形成时代及演化过程,对隆木岩体中的黑云母花岗岩与似斑状黑云母二长花岗岩进行LA-ICP-MS锆石U-Pb定年和同位素地球化学研究。结果表明:黑云母花岗岩与似斑状黑云母二长花岗岩的锆石U-Pb定年结果分别为(457±6)、(450±9)Ma,表明岩体形成于晚奥陶世;岩体铝饱和指数为1.11～1.29,K2O与Na2O含量(质量分数)之比为0.97～1.51,属强过铝质及高钾钙碱性岩石;根据ACF图解,岩体投影于S型花岗岩区域内;岩体Rb、Th+U、La+Ce、P、Nd、Zr+Hf+Sm相对富集,而Ba、Nb、Sr、Ti相对亏损,总体上属于低Ba、低Sr的花岗岩;岩体Rb与Sr含量之比为0.60～2.82,平均值为1.68,明显高于大陆地壳与上地壳的平均值,具壳源花岗岩特征;根据A/MF-C/MF图解,岩体物源区为砂质岩;岩体稀土元素含量总量偏低,为(113～176)×10-6,轻稀土元素富集明显,配分模式明显呈右倾型,Eu异常为0.38～0.67,Eu亏损程度中等偏高;化学成分显示,岩体属于强过铝质高钾钙碱性S型花岗岩,是一种壳源花岗岩,岩浆源区为成熟上地壳的砂质岩源区;构造判别图解、年龄信息及野外特征表明,岩体形成于后碰撞伸展构造环境。总之,隆木岩体形成于早古生代晚期的加里东构造运动,是华夏古陆块与扬子古陆块在新元古代碰撞拼贴之后裂解、在中奥陶世再次发生陆内碰撞使得地壳加厚部分重融、造山后期地壳伸展减薄、熔融物质上升侵位形成的岩体。     

北秦岭孤山坪地区辉长岩地球化学特征、锆石U-Pb年龄及Lu-Hf同位素组成

北秦岭孤山坪地区辉长岩的研究程度较低,而辉长岩通常是下地壳或上地幔玄武质岩浆结晶的产物,可以在一定程度上反映特定地质时代壳幔演化格局。为了研究其成因和形成机制,对其锆石U-Pb年代学、岩石地球化学及锆石Hf同位素进行了研究。结果表明:辉长岩的侵位结晶年龄为（457.4±1.4）Ma,即形成于晚奥陶世;总体上富集轻稀土元素和大离子亲石元素K、Rb、Ba、Sr,相对亏损高场强元素Nb、P、Ti、Zr,指示其可能形成于活动陆缘弧环境;锆石ε_Hf（t）=6.4~9.1,一阶段模式年龄（t_DM1=822~708 Ma）和二阶段模式年龄（t_DM2=1 268~1 025 Ma）均大于锆石结晶年龄。综合研究认为,孤山坪地区辉长岩原始岩浆应来源于受俯冲流体交代作用改造的富集型地幔,可能形成于二郎坪群早期岛弧与秦岭地块之间的弧陆碰撞所导致的增生造山作用过程,代表了晚奥陶世二郎坪群由岛弧向弧后盆地转化的初始岩浆记录。本研究可以为北秦岭早古生代构造演化的厘定提供进一步的约束资料。      

Discovery of Late Permian Jianshanzi volcanic rocks in Qinghe valley of northern Liaoning and its geologic significance

Jianshanzi volcanic rocks at Qinghe valley in the northern Liaoning were considered belonging to Early Proterozoie Gaojiayu Formation of Liaohe Group, or to Early Cambrian Beidagou Formation of Qinghezhen Group, or Middle-Late Proterozoic Shenjiapu Formation-Complex of Kaiyuan Group-complex. Dating the zircons from the dacite with schistosity is 2 506 Ma in method of U-Pb （SHRIMP）. This evidence indicates the rocks may be referred to Late Permian in age. Discovery of the rocks is significant to re-recognize stratigraphic property of ＂Liaohe Group＂, regional geoteetonie location and revolution of orogenic zone in Qinghe valley of the northern Liaoning.