Laser probe <Superscript>40</Superscript>Ar-<Superscript>39</Superscript>Ar ages of metasomatic K-feldspar from the Hougou gold deposit,northwestern Hebei Province,China     

Xingwang?Xu  Xinping?CaiEmail author  Yulin?Liu  Baolin?Zhang 《中国科学D辑(英文版)》2002,45(6):559-564

The Hougou gold deposit in northwestern Hebei is a typical K-metasomatism-related gold deposit hosted by K-altered rocks overprinting alkali intrusive rocks. In order to determine the age and pulse intervals of K-metasomatism in this gold deposit, some metasomatic K-feldspars from K-altered rocks are selected to measure their formation time by laser probe ⁴⁰Ar-³⁹Ar dating method. The new analyzing data show that these metasomatic K-feldspar formed during 202.6 Ma and 176.7 Ma, and the corresponding K-metasomatism and associated gold mineralization occurred in the early stage of Mesozoic era. The pulse intervals of K-metasomatism in the Hougou area are estimated to be about 4 Ma.  相似文献   

Laser probe 40Ar-39Ar ages of metasomatic K-feldspar from the Hougou gold deposit, northwestern Hebei Province, China   总被引：1，自引：0，他引：1  

徐兴旺  蔡新平  刘玉林  张宝林 《中国科学D辑(英文版)》2002,45(6)

The Hougou gold deposit in northwestern Hebei is a typical K-metasomatism-related gold deposit hosted by K-altered rocks overprinting alkali intrusive rocks. In order to determine the age and pulse intervals of K-metasomatism in this gold deposit, some metasomatic K-feldspars from K-altered rocks are selected to measure their formation time by laser probe 40Ar-39Ar dating method. The new analyzing data show that these metasomatic K-feldspar formed during 202.6 Ma and 176.7 Ma, and the corresponding K-metasomatism and associated gold mineralization occurred in the early stage of Mesozoic era. The pulse intervals of K-metasomatism in the Hougou area are estimated to be about 4 Ma.  相似文献   

红十字湖地区伟晶花岗岩及其伟晶岩中钾长石的地球化学演化   总被引：1，自引：0，他引：1  

王贤觉 Cerny  P 《矿物学报》1992,12(1):18-25

红十字湖地区伟晶花岗岩-电气石伟晶岩-锂云母伟晶岩系列中的钾长石均为低(最大)微斜长石,Al的有序度高,t_1o≥0.95,△为0.88～0.99。Rb、Cs高达47092ppm和7750ppm,是含Rb、Cs最高的钾长石。Rb、Cs的大量存在导致晶胞参数a,V值明显增大。中等程度的Rb、Cs含量不影响Al的有序化,特别是Al从(t_2o+t_2m)→(t_1m+t_1o)的第一阶段,而高(Rb+Cs)含量(>1%)可以影响Al的有序化过程,特别是Al从t_1m→t_1o的第二阶段。这种影响与温度等条件相比是次要的因素。  相似文献   

钾长石的热释光特征   总被引：1，自引：0，他引：1  

李虎侯  卢良才 《矿物学报》1989,9(1):82-88

本文根据不同产状和不同种类的10块钾长石标本的热释光特性分析表明,钾长石的热释光特性不仅取决于矿物晶体的产状和化学成分。而主要还取决于晶体精细结构的特征。钾长石的热释光特性既有差异又存在许多共性,它们存在共同的高温区热释光峰,矿物自身的内辐射场恒定,同时对β辐射的热释光响应敏灵度很高,对阳光的敏感度也很高,这几点共性正是钾长石可以作为热释光断代的基础。  相似文献   

Metamorphic evolution of diamond-bearing and associated rocks from the Kokchetav Massif, northern Kazakhstan   总被引：10，自引：2，他引：10  

R. Y. ZHANG  J. G. LIOU  W. G. ERNST  R. G. COLEMAN  N. V. SOBOLEV  & V. S. SHATSKY 《Journal of Metamorphic Geology》1997,15(4):479-496

Representative diamond-bearing gneisses and dolomitic marble, eclogite and Ti-clinohumite-bearing garnet peridotite from Unit I at Kumdy Kol and whiteschist from Unit II at Kulet, eastern Kokchetav Massif, northern Kazakhstan, were studied. Diamond-bearing gneisses contain variable assemblages, including Grt+Bt+Qtz±Pl±Kfs±Zo±Chl±Tur±Cal and minor Ap, Rt and Zrn; abundant inclusions of diamond, graphite+chlorite (or calcite), phengite, clinopyroxene, K-feldspar, biotite, rutile, titanite, calcite and zircon occur in garnet. Diamond-bearing dolomitic marbles consist of Dol+Di±Grt+Phl; inclusions of diamond, dolomite±graphite, biotite, and clinopyroxene were identified in garnet. Whiteschists carry the assemblage Ky+Tlc+Grt+Rt; garnet shows compositional zoning, and contains abundant inclusions of talc, kyanite and rutile with minor phlogopite, chlorite, margarite and zoisite. Inclusions and zoning patterns of garnet delineate the prograde P–T path. Inclusions of quartz pseudomorphs after coesite were identified in garnet from both eclogite and gneiss. Other ultrahigh-pressure (UHP) indicators include Na-bearing garnet (up to 0.14 wt% Na₂O) with omphacitic Cpx in eclogite, occurrence of high-K diopside (up to 1.56 wt% K₂O) and phlogopite in diamond-bearing dolomitic marble, and Cr-bearing kyanite in whiteschist. These UHP rocks exhibit at least three stages of metamorphic recrystallization. The Fe-Mg partitioning between clinopyroxene and garnet yields a peak temperature of 800–1000 °C at P >40 kbar for diamond-bearing rocks, and about 740–780 °C at >28–35 kbar for eclogite, whiteschist and Ti-bearing garnet peridotite. The formation of symplectitic plagioclase+amphibole after clinopyroxene, and replacement of garnet by biotite, amphibole, or plagioclase mark retrograde amphibolite facies recrystallization at 650–680 °C and pressure less than about 10 kbar. The exsolution of calcite from dolomite, and development of matrix chlorite and actinolite imply an even lower grade greenschist facies overprint at c. 420 °C and 2–3 kbar. A clockwise P–T path suggests that supracrustal sediments together with basaltic and ultramafic lenses apparently were subjected to UHP subduction-zone metamorphism within the diamond stability field. Tectonic mixing may have occurred prior to UHP metamorphism at mantle depths. During subsequent exhumation and juxtaposition of many other tectonic units, intense deformation chaotically mixed and mylonitized these lithotectonic assemblages.  相似文献   

冈底斯斑岩铜矿成矿时代及青藏高原隆升   总被引：80，自引：23，他引：80       下载免费PDF全文

芮宗瑶  侯增谦  曲晓明  张立生  王龙生  刘玉琳 《矿床地质》2003,22(3):217-225

通过离子探针、K_Ar法和Re_Os法测得冈底斯斑岩铜矿带的成矿年龄。冈底斯斑岩铜矿带中驱龙石英二长花岗斑岩的SHRIMP年龄为 (17.5 8± 0 .74 )Ma ,冲江二长花岗斑岩的SHRIMP年龄为 (15 .6 0± 0 .5 2 )Ma,冲江闪长玢岩的SHRIMP年龄为 (14 .5 4± 0 .6 5 )Ma。驱龙和冲江含矿斑岩钾长石的K_Ar年龄分别为 (16 .4 3± 0 .31)Ma和 (15 .77± 0 .4 5 )Ma ,矿石中辉钼矿的Re_Os年龄分别为 (15 .99± 0 .32 )Ma和 (14 .85± 0 .6 9)Ma。因此驱龙和冲江斑岩铜矿的成矿年龄约束于 (17.5 8± 0 .74 )Ma～ (14 .85± 0 .6 9)Ma之间。驱龙石英二长花岗斑岩为强矿化岩石 ,冲江二长花岗岩斑岩为中等矿化岩石 ,冲江闪长玢岩为未矿化岩石 ,三者的年龄依次变小 ,放射性元素2 0 6Pb、U和Th含量则依次增高。这表明随着壳源物质混合的增强 ,铜矿化渐弱。立足于大西洋底栖有孔虫氧同位素变化和印度洋北部海底沉积扇的沉积速率变化来看青藏高原隆升 ,认为玉龙矿带和冈底斯矿带斑岩铜矿是在青藏高原两次最明显的地壳运动中形成的  相似文献   

Albany K-Feldspar: A New Pb Isotope Reference Material     

Janne Liebmann  Bryant Ware  Michael I.H. Hartnady  Christopher L. Kirkland  Nicholas E. Timms  Noreen J. Evans 《Geostandards and Geoanalytical Research》2023,47(3):637-655

Lead isotopes are a powerful and versatile tool to elucidate fundamental geological problems related to the formation and evolution of continental crust. K-feldspar is a popular target for Pb isotope measurement as it is prevalent in many rock types and tends to capture the initial Pb isotope composition of its parental magma. We present data for a new Pb isotope reference material: Albany K-feldspar; as well as updated data for Shap K-feldspar. Results of Pb double-spike TIMS for Albany K-feldspar are ²⁰⁶Pb/²⁰⁴Pb = 16.7872 ± 0.0062, ²⁰⁷Pb/²⁰⁴Pb = 15.5640 ± 0.0056, and ²⁰⁸Pb/²⁰⁴Pb = 36.6600 ± 0.0168 (2s). TIMS measurement results for Shap K-feldspar indicate two isotopically distinct Pb populations. LA-MC-ICP-MS, with a spatial resolution as high as 15 μm, indicates a homogeneous Pb isotopic composition in Albany K-feldspar. In accord with previous studies, our results show that scatter in the measured Pb isotope ratios, related to the low natural isotopic abundance of ²⁰⁴Pb, along with the effect of isobaric ²⁰⁴Hg-²⁰⁴Pb interference, increases at lower count rates. However, the mean Pb isotope ratios measured via LA-MC-ICP-MS using a range of spot sizes are in excellent agreement with TIMS results thus highlighting the feasibility of Pb isotope determination via LA-MC-ICP-MS to access geological information preserved in small crystals, including mineral inclusions.  相似文献   

宜昌第四纪砾石层钾长石主、微量元素物源研究及其地质意义     

林旭  刘海金  吴中海  刘维明  张洋  陈济鑫 《地质力学学报》2021,27(6):1024-1034

位于长江三峡出口的宜昌地区分布着一套第四纪砂砾石层,详细记录了区域内古环境变迁以及长江的形成与演化,但这些砾石层何时与长江上游物质建立物源关系一直存在较大争议。而钾长石是河流沉积物中常见的矿物,其地球化学元素组成在不同区域内存在显著差异,是进行河流物源对比研究的理想矿物。基于此,利用激光剥蚀电感耦合等离子质谱仪（LA-ICP-MS）对宜昌第四纪砾石层和宜昌以上长江流域开展碎屑钾长石原位主微量元素和主成分（PCA）分析,结合砾石层已发表的地层沉积年龄,综合区域内已发表的研究结果,系统对比分析宜昌砾石层与长江上游物质建立物源联系的时间,结果表明在1.15 Ma时宜昌砾石层和长江流域存在物源关系;在0.75 Ma时随着长江上游水系的拓展与调整,有新物源区的物质进入长江。这些物源变化现象,主要体现了1.2~0.7 Ma期间长江流域受东亚和南亚夏季风的气候影响出现的沉积过程。   相似文献   

扬子板块北缘光雾山地区钾长花岗岩年代学、地球化学特征及构造意义     

魏国安  邹光富  潘伟奇  罗茂金  马志鑫  毛琼  余学磊 《矿物岩石》2019,39(2):14-24

为了限定扬子板块北缘地区新元古代岩浆活动事件的准确时间及和探讨岩石成因,本文对出露于四川省南江县光雾山钾长花岗岩进行了LA-ICP-MS锆石U-Pb定年和岩石地球化学研究。结果表明光雾山地区钾长花岗岩锆石U-Pb年龄为836.3Ma±8.3Ma,属于新元古代花岗岩。岩石具有高w(SiO2)(72.68%~78.10%),w(K2O)(4.26%~5.32%),w(Na2O)(1.68%~3.38%),相对富钾(K2O/Na2O=1.12~2.54),高碱(w(Na2O+K2O)=7.64%~8.99%),低P2O5含量等特征,铝饱和指数A/CNK=0.99~1.49,光雾山花岗岩属于过铝质高钾钙碱性花岗岩。岩石具有轻稀土元素相对富集,重稀土元素亏损的特征,具有明显Eu负异常,δEu为0.48~0.73。光雾山花岗岩微量元素表现出Rb,Th,K,Nd,Sm元素富集,Ba,Nb,Ta,Sr,P,Ti元素亏损的特点。地球化学研究表明,光雾山钾长花岗岩主要以粘土岩部分熔融为主及少部分含粘土的变质杂砂岩部分熔融形成的。岩浆可能来源于本区结晶基底新太古界-古元古界后河岩群和褶皱基底中-新元古界火地亚群中深变质岩为代表的地壳物质的部分熔融产物,为壳源成因类型,具有岛弧型花岗岩特征,形成于岛弧构造环境。光雾山钾长花岗岩的形成是新元古界时期扬子板块与华北板块之间的俯冲碰撞、岛弧形成构造演化过程中使区域地壳不断加厚和地壳深融作用的响应。扬子陆块北缘南江地区约836Ma同碰撞岛弧型钾长花岗岩的发现,表明该地区在约836Ma时为Rodinia超大陆汇聚形成阶段,此时期该区Rodinia超大陆尚未进入大陆裂解阶段。  相似文献   

内蒙古赵井沟钾长花岗岩锆石U-Pb定年、Hf同位素和岩石地球化学特征     

张超  李志丹  李效广  奥琮  俞礽安  王佳营  李光耀  张祺  段明 《岩石矿物学杂志》2019,38(3):303-317

赵井沟铌钽矿与区内花岗岩关系非常密切,锆石LA-ICP-MS U-Pb定年结果表明矿区内黑云母钾长花岗岩形成时代为125±1 Ma。岩石地球化学分析结果显示,矿区内晚中生代岩浆岩为准铝质-弱过铝质碱性岩类,属于高钾钙碱性系列,具有轻稀土元素富集、Eu强负异常、大离子亲石元素(Rb、Th、U)和高场强元素(Hf、Y)强烈富集的地球化学特征,属于A1亚类的A型花岗岩;锆石~(176)Hf/~(177)Hf值介于0. 000 5～0. 003 0之间,ε_(Hf)(t)值为-15. 42～-5. 55,对应的模式年龄t_(DM2)变化于2 247～1 640 Ma之间。花岗岩浆主要来源于地壳物质部分熔融的产物。  相似文献