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51.
华北克拉通北缘中段古元古代强过铝质花岗岩地球化学特征及其构造意义 总被引：3，自引：2，他引：3
华北克拉通北缘中段沿集宁-凉城-千里山一线分布着大量的强过铝质花岗岩.与一般强过铝质花岗岩相比,其SiO2含量、Al2O3/TiO2比值(小于100)、Rb/Sr比值和Rb/Ba比值低,但CaO/Na2O比值高(大于0.3).稀土元素复杂,正Eu异常、负Eu异常、Eu异常不明显均发育,大致可以分成2种类型:第一类具有中等程度轻稀土富集、重稀土平缓;第二类轻稀土特征与第一类一致,但其重稀土变化大.稀土元素特征不一致主要是由于其源岩不同.LILE(K、Rb、Ba)相对富集,HSFE(Nb、Ti、P)亏损,这种地球化学特征暗示该区强过铝质花岗岩的源区成分为杂砂岩,熔融温度较高,来源较深,其构造环境与澳大利亚拉克伦造山带一致,属高温型碰撞带,应为华北克拉通西部陆块和东北陆块古元古代碰撞峰期后岩石圈伸展的产物. 相似文献
52.
湘东北新元古代过铝质花岗岩的岩石地球化学特征及其成因讨论 总被引：2，自引：4，他引：2
湘东北位于扬子板块东南缘江南造山带中段,出露的新元古代花岗岩有长三背、大围山和葛藤岭等岩体,同属于九岭岩体的一部分。湘东北新元古代花岗岩SiO2含量变化于60%~72%、CaO为0.6%~3%、Na2O为1.98%~3.72%、K2O为2.95%~4.99%之间,A/CNK>1.1,富集K、Rb、Ba等大离子亲石元素(LILE)和轻稀土元素(LREE/HREE=3.1~10.5)、Eu负异常明显(δEu=0.37~0.58),而Nb、Ta、Ti等高场强元素(HFSE)相对亏损。这些特征表明湘东北新元古代花岗岩来源于过铝质熔体,岩石类型上类似于富黑云母过铝花岗岩类(CPG),可能来源于富黑云母的变泥质沉积岩的熔融,如中元古代冷家溪群变质沉积岩等,形成于同碰撞环境,可能与陆壳加厚导致的剪切重熔有关。 相似文献
53.
湖南衡阳燕山早期川口过铝花岗岩地球化学特征、成因与构造环境 总被引：10，自引：0，他引：10
川口过铝花岗岩为二云母二长花岗岩,高硅、中碱,SiO2和K2O含量分别平均为75.71%和4.39%,Na2O K2O平均为7.57%,K2O/Na2O平均为1.43,Al2O3平均为13.28%,总体属过铝—强过铝质钙碱性花岗岩类。Ba、Nb、Sr、Eu、Ti等元素表现为较强烈的亏损,Rb、U、Ta、Nd、Hf、Sm、Y Yb等则相对富集;ΣREE平均仅67.18×10-6,(La/Yb)N平均为2.21,δEu值平均为0.16。ISr为0.75093,εSr(t)为659,εNd(t)为-11.82,t2DM为1.92Ga,与湘桂内陆带花岗岩的背景值(2.4~1.8Ga)和区域基底的时代(2.7~1.7Ga)相吻合。川口岩体岩浆来源为中地壳结晶基底,属典型S型花岗岩;岩浆存在源于泥质岩的“低温”和源于砂岩的“高温”两种不同类型,至少有两个岩浆来源;岩体形成于后造山构造环境。分析认为,深部岩石圈拆沉与壳幔相互作用的规模差异,是造成湘东南燕山早期花岗岩一般为准铝—弱过铝质并有幔源物质加入,而川口岩体为过铝—强过铝质壳源花岗岩的原因。 相似文献
54.
Liao Zhongli Mo Xuanxue Pan Guitang Zhu Dicheng Wang Liquan Zhao Zhidan Geng Quanru Xiong Xingguo Dong Guochen 《Frontiers of Earth Science》2007,1(2):194-205
There are 61 major peraluminous granitic bodies in Tibet (TPGs) along the south of the Bangong Co-Gêrzê-Amdo-Nujiang suture,
whose lithology includes tourmaline granite, muscovite granite and two-mica granite. The TPGs have SiO2 = 65.7%−79.52%, K2O + Na2O = 2.20%−12.51%, K2O/Na2O = 0.49−1.04 and A/CNK = 1.04−1.38. Al2O3 gradually decreases and the other oxides disperse with the increase in SiO2. The rock series is mainly calc-alk series with high potassium. It has typical characteristics of strongly peraluminous granite.
Based on the aluminum saturation index and QAP plots, the peraluminous granite plot is mostly within the continental collision
granite (CCG) field, indicating that the peraluminous granites in Tibet formed in a continental collisional setting. Ab-Or-Q-H2O phase diagram indicates the pressure of 0.5 × 108−2 × 108 Pa in TPGs, from which it can be deduced that the forming temperature was under 700°C. The TPGs mainly occurred at the collision
stage between two continental crust plates, and the original magma is rooted in the remelting from the upper crust. It is
the S-type granite in petrogenesis. The South Gandise belt and the Lhagoi Kangri belt have similar characteristics, suggesting
that the two belts have the same magma source and the same tectonic setting.
Translated from Acta Geologica Sinica, 2006, 80(9): 1329–1341 [译自: 地质学报] 相似文献
55.
东天山小黄山花岗岩位于阿齐克库都克断裂和康古尔塔格断裂之间的构造带,为一类具有白云母、石榴子石等矿物的S型花岗岩,属于强过铝质花岗岩类。其LA- ICP- MS 锆石U- Pb同位素测年结果为835. 4±9. 0 Ma,地球化学特征说明此花岗岩为后碰撞岩浆作用而成,属于新元古代Rodinia超大陆拼贴- 裂解事件的产物。此外,该前寒武纪岩体的发现结合康古尔塔格—镜儿泉沿线出露的蛇绿岩、含蓝晶石和石榴子石的变质岩系,以及康古尔塔格断裂带南北两侧区域地层的差异,可以将康古尔塔格断裂带作为分隔中天山和北天山构造带的重要依据。 相似文献
56.
川西甲基卡二云母花岗岩与伟晶岩脉地球化学特征及其地质意义 总被引：1，自引：0，他引：1
对川西甲基卡地区二云母花岗岩及伟晶岩脉的岩石学特征、地球化学特征进行了分析,探讨了二云母花岗岩物质来源、构造背景及其与伟晶岩脉的成因联系。分析结果表明,甲基卡二云母花岗岩的SiO_2含量在73.93%~75.06%之间;全碱含量7.90%~8.36%,钾质含量较高,属高钾钙碱性系列岩石;Al_2O_3含量为14.24%~14.77%,A/CNK=1.14~1.24,具强过铝质S型花岗岩特征;ΣREE=31.18×10~(-6)~41.67×10~(-6),LREE/HREE=4.15~6.41,δEu=0.46~0.70;CaO/Na_2O=0.07~0.12(0.3),指示其物源可能是含砂屑物质极少的泥质岩;Al_2O_3/TiO_2=133.1~279.8,比值较高,表明甲基卡二云母花岗岩属高压低温型后碰撞强过铝质岩石。花岗伟晶岩脉SiO_2含量在72.59%~80.91%之间,全碱含量5.26%~10.60%,Al_2O_3含量11.79%~17.64%,σ=0.74~3.80,A/CNK=0.98~2.38,ΣREE=4.03×10~(-6)~8.29×10~(-6),LREE/HREE=2.61~10.40,δEu=0.18~0.68,与岩体差异明显,主、微量元素含量变化也较大。甲基卡二云母花岗岩与伟晶岩脉有密切的成因联系。岩浆不混溶作用可能是形成甲基卡含矿伟晶岩脉的关键因素,花岗质岩浆在上升过程中通过不混溶作用分离出富含挥发分的伟晶岩熔体,在运移或侵位过程中可能交代围岩矿物而使稀有金属元素进一步富集。二云母花岗岩浆和伟晶岩熔体性质的不同导致稀土元素和Th、Sr、Ti、Y、Rb、N等微量元素在两者中含量有明显差异。伟晶岩熔体在运移或就位过程中所经的路径不同和周围环境的差异导致不同位置产出的伟晶岩的元素含量有较大的变化。与二云母花岗岩相比,花岗伟晶岩的形成演化具有一定的跳跃性。 相似文献
57.
As an important part of the early Mesozoic granites in the South Qinling tectonic belt (SQTB), the Guangtoushan pluton provides a material basis for research on the composition of magma sources and the effects of peritectic assemblage entrainment (PAE) on the changes in the granite composition. As shown by the results of LA-ICP-MS zircon U-Pb dating, the Guangtoushan pluton was emplaced during the Late Triassic (214–212 Ma) and was formed in the post-collision stage between the SQTB and the Yangtze plate. The collected samples had high SiO2 content and low Cr and Ni contents, indicating that the magmas did not undergo significant crust-mantle mixing during their evolution. The Guangtoushan granitoids were distributed along the trend line of magmatic fractional crystallization in the F–An–Or diagram. This result, combined with the relatively homogeneous Sr-Nd isotopic composition, implies that the Guangtoushan pluton underwent slight assimilation and contamination. As can be inferred from the comparison between the compositions of the Guangtoushan granitoids and various fluid-absent experimental melts, the magma sources of the Guangtoushan granitoids contain a variety of materials, such as graywackes, pyroclastic graywackes, and pelites and are not derived from lower crustal mafic rocks. The correlation between the maficity and the major and trace elements further indicates that the strongly peraluminous granitoids from the Guangtoushan pluton was formed by the partial melting of biotite-bearing crustal rocks and its magmatic evolution was accompanied by the entrainment of clinopyroxenes and accessory minerals. 相似文献
58.
A. Pesquera P. P. Gil-Crespo J. Torres-Ruiz E. Roda-Robles 《International Geology Review》2018,60(2):157-187
The Jálama pluton (JP) is a Variscan peraluminous granitoid that intruded into low-grade metasediments from the Central Iberian Zone (CIZ). It comprises a sillimanite-bearing two-mica monzogranite in the inner zone, followed by a tourmaline-bearing two-mica monzogranite, and a marginal tourmaline-muscovite leucogranite in the northern half of the pluton. Microgranitoid enclaves and metasedimentary xenoliths occur locally in monzogranites. The change in rock type from the central monzogranite to the marginal leucogranite corresponds to decreasing TiO2, MgO, FeO, CaO, Sr, Ba, Zr, and ΣREE, and increasing SiO2, Na2O, P2O5, Rb, Li, Cs, Ta, Sn, and W. Fe/(Fe+Mg) ratios in biotite, muscovite and tourmaline increase with increasing Fe/(Fe+Mg) in bulk rock, suggesting an important control of the bulk-rock composition on mineral chemistry. The high peraluminosity, the low CaO and high P contents, as well as the similarity of ε(Nd)300 values in both the granites and metasediments of the southern CIZ constitute strong evidences for a crustal origin of the granite suite, probably by melting of these metasedimentary rocks. Field and petrographic observations, together with mineralogical and geochemical data, suggest that assimilation and mingling/mixing acted in concert with fractional crystallization during the formation of the JP. These processes may also have been important in the evolution of other granitoids from this region. 相似文献
59.
内蒙古苏莫查干地区的燕山期花岗岩体夹持于二连浩特-贺根山和索伦山-西拉木伦河深大断裂之间,其代表性岩石样品以富K、Al、Rb、Th和轻稀土元素,亏损Sr、Ti、P和Eu为特点,属高钾钙碱性过铝质花岗岩.钕同位素研究表明,岩石全岩样品的εNd(t)变化范围为0.77～-4.65,t2DM变化范围为869～1 310 Ma(多集中于1 072 ～1 310 Ma),与兴蒙造山带中的微陆块花岗岩相似.铅同位素的206Pb/204Pb=18.114～19.150,平均18.658;207Pb/204Pb=15.517～15.598,平均15.556;208Pb/204Pb=38.384～39.054,平均38.614;μ=9.2～9.5,平均9.37.所有数据点均投绘在造山带与地幔Pb演化线之间.主元素、微量元素、钕和铅同位素数据表明,本区燕山期花岗岩可能是在华北板块和西伯利亚板块碰撞造山后的伸展构造环境中,壳幔源物质通过物理混合后,再次发生重熔、成浆和结晶分异作用的产物,并且与该区的萤石和贱金属成矿作用具有密切的时空和成因联系. 相似文献
60.
西藏过铝花岗岩副矿物特征及岩石成因意义 总被引：6，自引：1，他引：5
副矿物的行为可以更直接地用来指示岩浆体系的地球化学过程,为了探讨过铝花岗岩的成因,对西藏过铝花岗岩体中的岩性、矿物组成、副矿物特征和锆石含量、晶体形态分布特征进行了研究,矿物岩石特征表明西藏过铝花岗岩富含白云母、电气石和钠质斜长石,属典型的含白云母过铝质花岗岩(MPG)。副矿物见有26种,副矿物组合主要有6种类型,其中主要为锆石 磷灰石 钛铁矿型,尤以锆石 磷灰石最为常见。结果表明,可明显分出5种锆石晶体形态;阴极发光图像中,锆石具有较好的晶形,并显示出清晰的岩浆锆石韵律环带结构。离子探针分析表明锆石具有高的Th/U值。西藏过铝花岗岩为岩浆成因,岩浆主要是由地壳物质部分熔融而成。副矿物组合曲线图的曲线形态可分为3种成因类型:壳源高铝型、壳源型和壳幔混合源型(壳幔同熔型),主要为壳源高铝型。不同构造岩浆带副矿物特征反映的成因信息不同,喜马拉雅带为壳源成因,而冈底斯带除了壳源成因之外,还有幔源成分的加入,反映了青藏高原岩石圈组成和演化的不均一性。 相似文献