Petrology of the diamond-grade eclogite in the Kokchetav Massif, northern Kazakhstan   总被引：2，自引：0，他引：2  

K. Okamoto  J. G. Liou and  Y. Ogasawara 《Island Arc》2000,9(3):379-399

Abstract The Kokchetav Massif of northern Kazakhstan is unique because of the abundant occurrence of microdiamond inclusions in garnet, zircon and clinopyroxene of metasediments. In order to determine precise pressure–temperature (P–T) conditions, we have systematically investigated mineral inclusions and the compositions of major silicates in Ti–clinohumite–garnet peridotite and diamond-grade eclogite from Kumdy–Kol. It was found that garnet peridotites from Kumdy–Kol contain assemblages of garnet, olivine, Ti–clinohumite and ilmenite. The garnet contains inclusions that are indicative of both ultrahigh pressure (UHP) and retrograde conditions. Inclusions of hydrous phases such as chlorite, amphibole and zoisite were formed at the post-UHP stage. The study also found that eclogite from Kumdy–Kol contains albite–augite symplectites after omphacitic pyroxene. The core of pyroxene (sodic augite) contains high K₂O (up to 1wt%; average 0.24wt%). Phengite is included in the core. Applying the K₂O-in-augite geobarometry, which is based on recent experiments, and the garnet–clinopyroxene (Grt–Cpx) geothermometer for peak metamorphism, the eclogites yield P–T estimates of > 6 GPa and > 1000 °C, and the diamond-grade eclogites yield lower temperature estimates at 900–1000 °C and 5 GPa.  相似文献   

龙游角闪橄榄岩的富流体相岩浆成因—矿物化学和微量元素地球化学制约   总被引：1，自引：0，他引：1  

唐红峰  刘丛强  周新民  徐夕生 《矿物学报》1999,19(3)

龙游角门橄榄岩山露于古老变质岩中．与围岩间的接触关系尚不清楚,但根据岩相学上矿物的平衡共生关系、岩石的矿物化学组成和角门橄榄岩及与之相关的花岗岩、金云母岩的微量元素地球化学特征．该橄榄岩很可能是富含流体组分的岩浆侵人而形成的,其形成的构造背景为具俯冲带性质的活动大陆边缘,富流体相的岩浆是由于其地幔源区受到了来自俯冲带的流体所交代的结果。  相似文献   

安徽歙县蛇绿岩中地幔橄榄岩的成因初探     

杨建明 《华东地质学院学报》1994,17(2):131-137,200

  相似文献   

安徽歙县蛇绿岩地球化学特征及形成构造环境   总被引：2，自引：0，他引：2       下载免费PDF全文

杨建明  王希斌  鲍佩声 《岩石矿物学杂志》1993,12(3):232-242

岩石化学、微量元素及稀土元素地球化研究表明:歙县蛇绿岩内地幔橄榄岩稀土元素配分为LREE富集型,不同于我国其他造山带地幔橄揽岩。歙县蛇绿岩壳层组合属于钙碱性和拉斑玄武岩间过渡系列,具类似的微量及稀土元素比值和稀土元素配分模型,且大离子亲石元素(LIL)和LREE高度富集。在Zr—Ti—Y和Hf—Ta—Th图解内,蛇绿岩基性熔岩成分点均落入钙碱性玄武岩区。结合岩石及区域地质资料,歙县蛇绿岩应形成于弧后(弧间)盆地环境。  相似文献   

Petrology of marble and peridotite in the Seiad ultramafic complex, northern California, USA   总被引：1，自引：0，他引：1  

J. E. LIEBERMAN  J. M. RICE 《Journal of Metamorphic Geology》1986,4(2):179-199

Abstract Peridotite and infolded marble of the Seiad ultramafic complex were recrystallized in the upper amphibolite facies as part of the regional progressive metamorphism of the Rattlesnake Creek terrane. Field relations, including the occurrence of metarodingites, and metasomatic zones between dissimilar rock types, demonstrate that the metasediments and serpentinized ultramafic rocks were juxtaposed prior to regional, barrovian metamorphism. Temperatures are estimated to have reached 760–800°C at pressures of 7–8 kbar during the peak of metamorphism. Four low-variance parageneses have been identified within a small (3 km²) area of the complex, which may reasonably be assumed to have formed under the same P and T conditions. Isobaric T-X co₂ diagrams of appropriate equilibria are presented for three different internally consistent sets of thermodynamic data. Despite the seemingly small numerical differences between the standard state thermodynamic properties of the data sets, only one diagram allows the four observed assemblages to coexist within a reasonable temperature range. All three phase diagrams require differences in fluid composition on the scale of a thin section; strong evidence for effective control of pore fluid composition by local mineral reactions during metamorphism.  相似文献   

电感耦合等离子体发射光谱法测定富镁铁橄榄岩类矿石中铜镍铁和氧化镁   总被引：2，自引：2，他引：0  

张旺强  王春妍  李瑞仙  巨力佩  陈月源  余志峰  毛振才 《岩矿测试》2011,30(2):195-199

样品经氢氟酸-盐酸-硝酸-高氯酸混合酸一次加入冷浸直接溶解,在5%(体积分数)的盐酸介质中,用电感耦合等离子体发射光谱法测定富镁铁橄榄岩类矿石中的铜、镍、铁、氧化镁,克服了传统分析方法操作繁琐、周期长、成本高,而过程难以控制等缺点。方法检出限为铜2.0μg/g,镍3.0μg/g,铁10μg/g,氧化镁20μg/g;精密度(RSD,n=12)为0.8%～4.1%。经国家一级标准物质分析验证,测定值与标准值吻合,结果准确可靠。对于富镁铁岩类矿石中含量较高的硫化物的测定,采用一次加混合酸冷浸除硫后,再加热分解样品,结果令人满意;其中含量较高的铁和氧化镁,采用分取稀释测定,减小基体干扰。建立的方法样品处理程序简单快速,线性范围宽,分析重现性好,适用于地质部门批量样品的分析。  相似文献   

Mantle peridotite in newly discovered far-inland subduction complex,southwest Arizona: initial report     

Gordon B. Haxel  Carl E. Jacobson  James H. Wittke 《International Geology Review》2015,57(5-8):871-892

The latest Cretaceous to early Palaeogene Orocopia Schist and related units are generally considered a low-angle subduction complex that underlies much of southern California and Arizona. A recently discovered exposure of Orocopia Schist at Cemetery Ridge west of Phoenix, Arizona, lies exceptionally far inland from the continental margin. Unexpectedly, this body of Orocopia Schist contains numerous blocks, as large as ~300 m, of variably serpentinized mantle peridotite. These are unique; elsewhere in the Orocopia and related schists, peridotite is rare and completely serpentinized. Peridotite and metaperidotite at Cemetery Ridge are of three principal types: (1) serpentinite and tremolite serpentinite, derived from dunite; (2) partially serpentinized harzburgite and olivine orthopyroxenite (collectively, harzburgite); and (3) granoblastic or schistose metasomatic rocks, derived from serpentinite, made largely of actinolite, calcic plagioclase, hercynite, and chlorite. In the serpentinite, paucity of relict olivine, relatively abundant magnetite (5%), and elevated Fe³⁺/Fe indicate advanced serpentinization. Harzburgite contains abundant orthopyroxene, only slightly serpentinized, and minor to moderate (1–15%) relict olivine. Mantle tectonite fabric is locally preserved. Several petrographic and geochemical characteristics of the peridotite at Cemetery Ridge are ambiguously similar to either abyssal or mantle-wedge (suprasubduction) peridotites and serpentinites. Least ambiguous are orthopyroxene compositions. Orthopyroxene is distinctively depleted in Al₂O₃, Cr₂O₃, and CaO, indicating mantle-wedge affinities. Initial interpretation of field and petrologic data suggests that the peridotite blocks in the Orocopia Schist subduction complex at Cemetery Ridge may be derived from the leading corner or edge of a mantle wedge, presumably in (pre-San Andreas fault) southwest California. However, derivation from a subducting plate is not precluded.  相似文献   

内蒙古索伦山菱镁矿成矿地质条件与找矿潜力分析     

薛建平 《地质与勘探》2017,53(3):464-471

产于内蒙古索伦山缝合带蛇绿岩中的菱镁矿,其深入研究对于菱镁矿的勘查、增加战略矿产资源以及国民经济的发展有重大意义。本文对内蒙古索伦山地区菱镁矿进行了系统的调查和研究,通过归纳索伦山地区菱镁矿矿床地质特征,探讨了索伦山地区菱镁矿矿床的成矿地质条件,在此基础上,分析和评价了索伦山地区菱镁矿的找矿潜力。索伦山地区菱镁矿产于索伦山蛇绿岩的地幔橄榄岩内,受岩体内部微小构造控制,矿体贫富受风化程度的制约,受超基性岩风化淋滤形成。菱镁矿与超基性岩硅质风化壳在成因上具有耦合关系,上部为风化淋滤残留物—超基性岩硅质风化壳,下部为风化淋滤的产物—菱镁矿。索伦山地区含菱镁矿的地幔橄榄岩岩体巨大,深部矿体众多,与国内西藏巴夏式菱镁矿在成矿条件和成矿模式方面相一致。所以,索伦山地区具有较大的菱镁矿找矿潜力。  相似文献   

Water contents of clinopyroxenes from sub‐arc mantle peridotites          下载免费PDF全文

Michael Turner  Simon Turner  Dawnika Blatter  Rene Maury  Michael Perfit  Gene Yogodzinski 《Island Arc》2017,26(5)

One poorly constrained reservoir of the Earth's water budget is that of clinopyroxene in metasomatised, mantle peridotites. This study presents reconnaissance Sensitive High‐Resolution, Ion Microprobe–Stable Isotope (SHRIMP–SI) determinations of the H₂O contents of (dominantly) clinopyroxenes in rare mantle xenoliths from four different subduction zones, i.e. Mexico, Kamchatka, Philippines, and New Britain (Tabar‐Feni island chain) as well as one intra‐plate setting (western Victoria). All of the sub‐arc xenoliths have been metasomatised and carry strong arc trace element signatures. Average measured H₂O contents of the pyroxenes range from 70 ppm to 510 ppm whereas calculated bulk H₂O contents range from 88 ppm to 3 737 ppm if the variable presence of amphibole is taken into account. In contrast, the intra‐plate, continental mantle xenolith from western Victoria has higher water contents (3 447 ppm) but was metasomatised by alkali and/or carbonatitic melts and does not carry a subduction‐related signature. Material similar to the sub‐arc peridotites can either be accreted to the base of the lithosphere or potentially be transported by convection deeper into the mantle where it will lose water due to amphibole breakdown.  相似文献