SHRIMP zircon U-Pb ages of Kalatongke No. 1 and Huangshandong Cu-Ni-bearing mafic-ultramafic complexes,North Xinjiang,and geological implications

In Xinjiang, northwestern China, there are some veryimportant magmatic Cu-Ni sulfide deposits hosted by ma-fic-ultramafic complexes. In addition to the Jingbulake inwestern Tianshan and the Xingdi in northeastern Tarimblock, the others are concentrated in the Kalatongke andHuangshan-Jingerquan mafic-ultramafic complex beltsand two largest Cu-Ni sulfide deposits occur in the Kala-tongke No.1 and Huangshandong complexes. In the pastdecade, a great number of researches have been conductedfo…     

U-Pb同位素定年标准锆石的Hf同位素

利用配有193 nm激光的Neptune多接收电感耦合等离子体质谱仪(LA-MC-ICPMS), 采用新发表的Yb的同位素丰度和本研究中测定出的Yb和Hf之间的质量歧视关系, 在原位和扫描模式下, 对标准锆石91500进行了一系列的Hf同位素测定实验. 结果显示, 不同束斑直径和模式下获得的Hf同位素比值在误差范围内相同, 并与文献报道值一致. 因此, 无论是原位还是扫描模式, 均可在LA-MC-ICPMS仪器上获得可信的锆石Hf同位素组成; 同时也表明我们所采用的干扰元素的校正方法对于取得令人满意的Hf同位素测量准确度是合适的. 运用上述方法对目前微区U-Pb定年工作中常用的4种标准锆石进行系统测定发现, 91500, CZ3, CN92-1和TEMORA的¹⁷⁶Hf/¹⁷⁷Hf比值分别为0.282316±4(n = 34); 0.281704±6 (n = 16), 0.282200±6 (n = 20)和0.282684±14 (n = 24), 对应的¹⁷⁶Lu/¹⁷⁷Hf平均值分别在0.00031, 0.000036, 0.00083和0.00127左右. 研究发现, 相对CN92-1和TEMORA而言, CZ3和91500具有非常狭窄和稳定的Lu/Hf比值及Hf同位素变化范围, 是Hf同位素LA-MC-ICPMS测定的理想标准锆石.     

Genesis of zircon and its constraints on interpretation of U-Pb age

Zircon U-Pb dating is the most commonly used method for isotopic geochronology. However, it has been a difficult issue when relating zircon U-Pb ages to metamorphic conditions in complex metamorphic rocks. Much progress has been made in the past decade with respect to the genesis of zircon and its constraints on interpretation of U-Pb age. Three methods have been proposed to link zircon U-Pb age to metamorphic conditions: ( i ) internal structure; ( ii ) trace element feature; (iii) mineral inclusion composition. Magmatic zircon shows typical oscillatory zoning and/or sector zoning, whereas metamorphic zircon has internal structures such as no zoned, weakly zoned, cloudy zoned, sector zoned, planar zoned, and patched zoned ones. Zircons formed in different geological environments generally have characteristic internal structures. Magmatic zircons from different rock types have variable trace element abundances, with a general trend of increasing trace element abundances in zircons from ultramafic through mafic to granitic rocks. Zircons formed under different metamorphic conditions have different trace element characteristics that can be used to relate their formation to metamorphic conditions. It is an effective way to relate zircon growth to certain P-T conditions by studying the trace element partitioning between coexisting metamorphic zircon and garnet in high-grade metamorphic rocks containing both zircon and garnet. Primary mineral inclusions in zircon can also provide unambiguous constraints on its formation conditions. Therefore, interpretation of zircon U-Pb ages can be constrained by its internal structure, trace element composition, mineral inclusion and so on.     

Hf isotope composition of zircons and implication for the petrogenesis of Yajiangqiao granite,Hunan Province,China

In the peralumineous granite of Yajiangqiao zircon population can be divided into two groups (i.e. Zircon Ⅰ and Zircon Ⅱ), which were formed in magmatic chamber and in emplacement place, respectively. The Hf isotope compositions of two stages of zircon show that the host magma was essentially derived from crustal material by melting. However, some higher 176Hf/177Hf ratios indicate that the granitic zircons should contain fine crystal of zircon formed in mantle-derived magma. In fact, the backscattered electron imaging and the electron microprobe analysis reveal that there is another type of zircon included within Zircon Ⅰ, which is quite different from Zircon Ⅰ and Zircon Ⅱ in morphology and chemistry. They are considered to be the product of the mantle-derived magma intruded into the granitic magma chamber at the beginning of anatexis. Thus,it is suggested that the formation of Yajiangqiao granite is related to the underplating of mantle magma.     

华北北缘早中生代岩浆底侵作用的年代学记录: 来自辽西晚中生代安山岩锆石U-Pb定年结果

通过对辽西晚中生代义县组顶部玻基方辉安山岩中锆石的阴极发光光谱和LA-ICP-MS定年,发现这些火山岩中锆石常具有环带结构．其中心为残留锆石,边缘部分为从寄主岩浆中结晶的锆石．边缘部分锆石的U-Pb年龄为116 Ma,与寄主火山岩的Ar-Ar年龄完全一致;而中心部分锆石的U-Pb年龄为254 Ma,与该区早中生代底侵麻粒岩中锆石的U-Pb年龄251 Ma一致．玻基方辉安山岩中单斜辉石捕虏晶与底侵麻粒岩中单斜辉石的组成类似．说明早中生代新增生下地壳的麻粒岩在晚中生代软流圈底辟上涌背景下遭到了改造和破坏,并且参与了晚中生代的玻基方辉安山岩的形成．     

Zircon U-Pb geochronology of basement metamorphic rocks in the Songliao Basin

Zircon LA-ICP MS U-Pb dating of six metamorphic rocks and a metagranite (breccia) from southern basement of the Songliao Basin are reported in order to constrain the formation ages of basement. The basement metamorphic rocks in the Songliao Basin mainly consist of metagabbro (L45-1), amphibolite (SN117), metarhyolitical tuff (G190), sericite (Ser) schist (N103), chlorite (Chl) schist (T5-1), biotite (Bi)-actinolite (Act)-quartz (Q) schist (Y205), and metagranite (L44-1). The cathodoluminesence (CL) images of the zircons from metagabbro (L45-1) and metagranite (L44-1) indicate that they have cores of magmatic origin and rims of metamorphic overgrowths. Their U-Pb isotopic ages are 1808±21 Ma and 1873±13 Ma, respectively. The zircons with oscillatory zoning from amphibolite (SN117) and Chl schist (T5-1), being similar to those of mafic igneous rocks, yield ages of 274 ± 3.4 Ma and 264 ± 3.2 Ma, re-spectively. The zircons from metarhyolitical tuff (G190) and Ser schist (N103) display typical magmatic growth zoning and yield ages of 424 ± 4.5 Ma and 287 ± 5.1Ma, respectively. Most of zircons from Bi-Act-Q schist (Y205) are round in shape and different in absorption degree in the CL images, implying their sedimentary detritals. U-Pb dating yield concordant ages of 427 ± 3.1Ma, 455 ± 12 Ma, 696 ± 13 Ma, 1384±62 Ma, 1649±36 Ma, 1778±18 Ma, 2450±9 Ma, 2579±10 Ma, 2793±4 Ma and 2953±14 Ma. The above-mentioned results indicate that the Precambrian crystalline basement (1808―1873 Ma) exists in the southern Songliao Basin and could be related to tectonic thrust, and that the Early Paleozoic (424―490 Ma) and Late Paleozoic magmatisms (264―292 Ma) also occur in the basin basement, which are consistent with the ages of the detrital zircons from Bi-Act-Q schist in the basement.     

Zircon SHRIMP U-Pb ages of the “Xinghuadukou Group” in Hanjiayuanzi and Xinlin areas and the “Zhalantun Group” in Inner Mongolia, Da Hinggan Mountains

A report is presented of SHRIMP zircon U-Pb dating data of meta-igneous and meta-sedimentary rocks of the Xinghuadukou Group(Xinlin-Hanjiayuanzi area,Heilongjiang Province)and meta-volcanic rocks of the Zhalantun Group(Zhalantun district,Inner Mongolia).The SHRIMP analyses show that the meta-igneous rocks from the Xinghuadukou Group formed at 506±10―547±46 Ma,belonging to Early-Middle Precambrian,whereas the meta-sedimentary rocks yielded detrital zircons,with ages of 1.0―1.2,1.6―1.8 and 2.5―2.6 Ga,indicative of deposition age at least<1.0 Ga. Meta-basic volcanic rocks from the Zhalantun Group have a formation age of 506±3 Ma.These data suggest that both the Xinghuadukou and Zhalantun Groups formed during Cambrian and/or Neoproterozoic time,rather than Paleoproterozoic time as previously thought.Early Precambrian inherited zircons in the meta-igneous rocks and numerous Precambrian detrital zircons in the meta-sedimentary rocks imply that these rocks were formed proximal to older crust.It is inferred that the Xinghuadukou and Zhalantun Groups represent Cambrian and/or Neoproterozoic vol- cano-sedimentary sequences formed in an active continental margin setting.     

～4.1 Ga xenocrystal zircon from Ordovician volcanic rocks in western part of North Qinlin80rosenic Belt

High-precision U-Pb dating by in situ LA-ICP-MS yields an age of 4079±5 Ma for a xenocrystal zircon from Ordovician volcanics of the Caotangou Group in western part of the North Qinling Orogenic Belt. As a result, the North Qinling Orogenic Belt becomes one of a few localities in the world that contain Hadean age records （4276±6 Ma and 4404±8 Ma detrital zircons from Jack Hill of the Yilgarn craton, 4016 Ma Acasta gneisses of the Wopmay Orogeny and Burang quartzite with detrital zircon of 4103 Ma in Tibet）. It is also the first report of the Hadean age in Phanerozoic volcanics. The finding of the 4.1 Ga xenocrystal zircon provides not only the geochronological record of the oldest crustal materials in China, but also the condition for further search for rocks forming in the region during the early time of the Earth＇s evolution. Thirty-six zircon U-Pb dates from the Ordovician volcanic rocks are subgrouped into seven generations that represent different tectono-magmatic events in the North Qinling Orogenic Belt. Among them, two periods of 0.9--1.5 Ga and 0.4--0.5 Ga are consistent with Mesoproterozoic and Early Paleozoic orogenies, respectively.     

正交设计研究锆铁红色料的合成

采用正交设计实验法研究了配方及工艺制度对锆铁红色料合成的影响，分析了各因素对锆铁红色料合成的影响趋势，得到了主次影响因素，并指出主要因素为：合成温度、矿化剂的种类、预处理方式，找到了利用常规的陶瓷颜料制备工艺合成锆铁红色料的最佳配合及合成工艺制度。详细讨论了锆铁红色料合成的影响因素，并探讨了锆铁红色料合成过程中各因素作用的机理，为锆铁红色料合成及生产提供了切实可行的实际生产和理论依据。