华南腹地白垩纪A型花岗岩类或碱性侵入岩年代学及其对华南晚中生代构造演化的制约   总被引：33，自引：14，他引：33  

王强赵振华  简平熊小林  包志伟戴橦谟许继峰  马金龙 《岩石学报》2005,21(3):795-808

华南腹地存在多个白垩纪的A型花岗岩类或碱性侵入岩,如安徽花山霓辉石钠闪石花岗岩、福建大沅村霓辉石钠铁闪石花岗岩、广东恶鸡脑霞石方钠石正长岩以及浙江大和山辉石石英正长斑岩、苏村晶洞钾长花岗岩。锆石SHRIMP和矿物的40Ar-39Ar年代学研究表明,这些岩石主要形成于137-86Ma。以本文的年代学研究为基础,并结合前人大量研究成果, 将华南晚中生代的A型花岗岩类或碱性侵入岩大致分成三期:(1)侏罗纪(184-152Ma)A型花岗岩类或碱性侵入岩,主要沿“十-杭裂谷带”南段分布,在赣南也有分布,可能与古太平洋板块低速斜向俯冲或平移所导致的走滑伸展或与不受古太平洋板块运动影响的岩石圈伸展有关;(2)早白垩世(139-123Ma)A型花岗岩类或碱性侵入岩,分布于政和-大埔断裂带以西,可能与古太平洋板块快速斜向俯冲所导致的弧后伸展或岩石圈减薄有关;(3)晚白垩世(101-86Ma)A型花岗岩类或碱性侵入岩,主要沿闽浙沿海地区分布,同时在华南腹地也有零星分布,可能与大陆边缘弧的塌陷(collapse)或俯冲洋壳反转(roll- back)后的岩石圈伸展有关。  相似文献   

金,铀,硅溶解性状的实验研究   总被引：5，自引：0，他引：5  

刘正义  张家富 《铀矿地质》1994,10(4):212-219

在ＰＨ２Ｏ为１５０ＭＰａ，ｐＨ为１０的Ｎａ２ＣＯ３溶液中混合花岗岩的金、铀、硅溶解实验表明，温度３５０—４００℃时有利于金的溶解，２００—３００℃时有利于铀溶解，而硅的溶解随温度的增加呈线性增长。在ＰＨ２Ｏ为１５０ＭＰａ，３５０℃状态下，铀、硅的溶解随Ｎａ２ＣＯ３浓度的增加而增加。当用ＨＣｌ调节Ｎａ２ＣＯ３溶液的ｐＨ值时，金偏向溶于碱性介质，铀偏向溶于酸性介质。在ＰＨ２Ｏ为１５０ＭＰ。，３５０℃不同的碱性溶液中，金与硫化物、氯化物，铀与碳酸盐或碳酸盐－硫化物关系密切，表现金的亲硫性和铀的亲氧性。“焙烧”实验表明，构造、岩浆活动等热事件对金、铀、硅溶解起促进作用。  相似文献   

Extension-related origin of magmas from a garnet-bearing source in the Los Tuxtlas volcanic field, Mexico     

Surendra P. Verma 《International Journal of Earth Sciences》2006,95(5):871-901

The Los Tuxtlas volcanic field (LTVF) of late Miocene to Recent age is a key area to understand the consequences of the current subduction of the Cocos plate beneath the North American plate, as well as the competing effects of the ongoing extension along the Gulf of Mexico coast. Geochemical and radiogenic (Sr, Nd, and Pb) isotope data are used to constrain the origin of these 7 Ma to Recent magmas in this area. The basanitic and alkaline basaltic rocks show highly steep light rare-earth element-enriched patterns implying residual garnet in their mantle source, whereas the evolved alkaline and sub-alkaline rocks have less steep rare-earth element patterns consistent with a contribution from the continental crust. Geochemical and isotope data from the LTVF are compared with those from continental rifts, extension-related areas, continental break-up regions, and island and continental arcs, including the Central American volcanic arc related to the subduction of the same oceanic plate (Cocos plate), as well as with those from the two nearby Mexican provinces [the Eastern Alkaline Province (EAP) and the eastern part of the Mexican Volcanic Belt (E-MVB)]. These data for the LTVF primitive rocks are similar to rifts, extension-related areas and continental break-up regions, including the two Mexican provinces, but different from island and continental arcs, including the northern part of the Central American Volcanic Arc (CAVA). The LTVF rocks show an unusual Th and U enrichment with respect to Ba and Rb, which also renders a distinct negative Nb anomaly (with respect to Th and K) in them. These rocks also show a negative Nb anomaly (with respect to Ba and La) that is similar to numerous rift, extension-related areas, and continental break-up regions, but distinct from all arcs around the world, indicating that the magma genesis processes in the LTVF are similar to those in rifts. The “Sr-shift”, shown to be a typical feature of most, if not all, island and continental arcs including the CAVA, is not present in the LTVF rocks. Numerous discrimination diagrams, including the new discriminant function diagrams, suggest a rift setting for the LTVF. An essentially extension-related origin of the LTVF is, therefore, inferred in this study. Furthermore, in the light of major and trace element data for LTVF primitive rocks and their modelling an incompatible element-enriched garnet-bearing source seems plausible. The LTVF source is likely to reside in the lithosphere rather than the asthenosphere although the asthenospheric contribution cannot be completely ruled out. The evolved alkaline and sub-alkaline rocks might have a lower crustal component. Finally, it appears that the LTVF shows more affinity to the EAP rather than to the Mexican Volcanic Belt (MVB), implying that the LTVF should probably be considered as a part of the EAP.  相似文献   

Spatial, temporal and geochemical characteristics of Silurian collision-zone magmatism, Newfoundland Appalachians: An example of a rapidly evolving magmatic system related to slab break-off   总被引：3，自引：0，他引：3  

Joseph B. Whalen  Vicki J. McNicoll  Cees R. van Staal  C. Johan Lissenberg  Frederick J. Longstaffe  George A. Jenner  Otto van Breeman 《Lithos》2006,89(3-4):377-404

Silurian plutonic suites in the Newfoundland Appalachians include abundant gabbro, monzogabbro and granite to granodiorite and lesser quartz diorite and tonalite. Most are medium- to high-K, but included are some low-K and shoshonitic mafic compositions. Felsic rocks are of both alkaline (A-type or within-plate granite (WPG)) and calc-alkaline volcanic arc granite (VAG) affinity. Mafic rocks include both arc-like (Nb/Th < 3) calc-alkaline and non-arc-like (Nb/Th > 3) transitional calc-alkaline basalt to continental tholeiitic affinity compositions. ε_Nd(T) values range from − 9.6 to + 5.4 and δ¹⁸O (VSMOW) values range from + 3.1 to + 13.2‰.

A rapid progression from exclusively arc-type to non-arc-like mafic and then contemporaneous WPG plus VAG magmatism has been documented using precise U–Pb zircon dating. Earlier arc-like plutonism indicates subduction, while asthenosphere-derived mafic magmas support slab break-off, due to subduction of a young, warm back-arc basin. Contemporaneous mafic magmas with arc and non-arc geochemical signatures may reflect tapping of asthenospheric and subcontinental lithospheric mantle (SCLM) sources and/or contamination of asthenosphere-derived magmas by SCLM or crust.

The brevity (< 5 Ma) of the mafic magmatic pulse agrees with the transient nature of magmatism associated with slab break-off. The subsequent ca. 1 to 2 m.y. period of voluminous WPG and VAG plutonism likely reflects mafic magma-driven partial melting of both SCLM and crustal sources, respectively. Continuation of VAG-like magmatism for an additional 2 to 5 m.y. may reflect lower solidus temperatures of crustal materials, enabling anatexis to continue after mantle melting ceased. East to west spatial variation of ε_Nd and (La/Yb)_CN in Silurian plutons suggests a transition from shallow melting of juvenile sources proximal to the collision zone to deeper melting of old source materials in the garnet-stability field further inboard.

Previous work has demonstrated that geochemical discriminaton of post-collisional granitoid magmatism (PCGM) is difficult in the absence of other constraints. Our example should contribute to the understanding and identification of PCGM if it can be employed as a ‘fingerprint’ for slab break-off-related PCGM within the Paleozoic geological record.  相似文献   

Geochemical assessment of the contaminant potential of granite fines produced during sawing and related processes associated to the dimension stone industry     

J. Delgado  A. Vzquez  R. Juncosa  V. Barrientos 《Journal of Geochemical Exploration》2006,88(1-3):24

Granite fines are inorganic wastes produced in the elaboration of dimension stone. Because of the increasing development of that industry in NW Spain, some concerns related to their classification as type of waste and their environmental impact have been raised. We have performed a detailed physicochemical, mineralogical and geomechanical characterization of the fines and the results make up the basis of several modeling exercises addressed to give answers to particular topics: the impact of high pH waters on the environment and the mobility of some toxic metals. Based on our analyses, we conclude that granite fines do not constitute a significant hazard to the quality of natural waters.  相似文献   

Selective leaching of antimony and arsenic from mechanically activated tetrahedrite,jamesonite and enargite     

P. Baláž  M. Achimovičová 《International Journal of Mineral Processing》2006

In this study, the changes in surface area, morphology and leachability of antimony and arsenic from tetrahedrite, jamesonite and enargite mechanically activated by a high-energy planetary mill were investigated. It appears that the leaching of antimony from tetrahedrite and jamesonite and arsenic from enargite in alkaline solution of sodium sulphide is temperature-sensitive reaction. The temperature dependencies of all reactions were investigated in the interval 313–363 K. Resulting experimental activation energies were E_a = 111–182 kJ mol^− 1 for mechanically activated minerals. The values of E_a are characteristic for processes controlled by surface chemical reactions.  相似文献   

新疆后造山碱性花岗岩的地质特征   总被引：2，自引：2，他引：2  

朱笑青王中刚  王元龙毕华 《岩石学报》2006,22(12):2945-2956

新疆地区碱性花岗岩分布很广泛,可以划分出十条岩带,它们主要分布在古生代岛弧、弧后盆地及隆起区,与板块缝合线、深断裂密切相关,并与蛇绿岩和陆相火山岩相伴生。同位素年代测定表明,本区碱性花岗岩的形成是紧随造山运动之后发生的,属于后造山花岗岩。因此,它们形成时的构造环境、岩石化学成分、矿物组成及微量元素特征等均与非造山花岗岩(A 型花岗岩)有一定的区别。在一个地区有这么多后造山碱性花岗岩分布,国内外并不多见,这是新疆地质的一个特色。  相似文献   

中国山东昌乐地区碱性玄武岩刚玉中记录的岩浆不混溶作用   总被引：2，自引：0，他引：2  

刘吉强 倪培沈昆  丁俊英 《岩石学报》2007,23(1):125-130

Abundant melt-and fluid inclusions occur in corundum megacrysts of alkaline basalt from the Changle area,Shandong province,eastern China.One type of melt inclusions,i.e.muhiphase melt inclusions(glass bubbles daughter minerals)were identified,which occur along growth zones of host corundum megacrysts.Microthermometry and laser Raman microprobe analysis were performed on the melt inclusions.The bubbles within the melt inclusions are confirmed to be CO_2-rich phase and the daughter minerals are probably silicates,such as augite and okenite.The results of high temperature homogenization experiment strongly suggest that two immiscible melts,i.e.a H_2O-and CO_2-rich melt and an anhydrous and CO_2-poor melt were trapped by melt inclusions in corundum megacryst.  相似文献   

Metallogenic age and metallogenic dynamic setting of the Boziguoer super-large rare-rare earth metal deposit in Xinjiang: Insights from monazite U-Th-Pb dating and graphite Laser Raman spectroscopySCIEI北大核心CSCD     

谢明材  韩春明  范宏瑞  杨奎锋  李兴辉  佘海东  梁改忠 《岩石学报》2023,(10):2927-2950

波孜果尔碱性岩型Nb-Ta-Rb-Zr-REE矿床位于塔里木克拉通北缘与南天山造山带的接合地段,是近年来在塔里木北缘碱性岩带中发现的规模最大的稀有-稀土综合性矿床。本文通过对含矿岩体中的独居石和晶质石墨包体开展成矿年代学和岩浆形成条件研究,结合含矿碱性岩全岩成分,揭示波孜果尔碱性岩型稀有-稀土金属矿床的岩石地球化学特征、晶质石墨对成岩/成矿的指示、稀土成矿时代和成矿动力学背景,并进一步总结区域成矿指示意义。研究发现,波孜果尔碱性岩以富含碱性暗色矿物(钠铁闪石和霓石)为特征,岩性以正长岩为主,有较高的稀土总量,富集轻稀土元素和高场强元素(Nb、Ta、Zr、Hf、Th、U等),亏损重稀土元素和Ba、Sr等大离子亲石元素,显示强烈的负Eu异常。通过对晶质石墨的研究发现,不同岩相组中石墨的拉曼谱峰相似,显示具有较高的结晶程度,岩浆演化从细晶到伟晶阶段,石墨的无序度增大,可能与烧绿石和锆石等含放射性元素矿物增多使得辐射加强的影响有关。估算石墨的结晶温度介于700~800℃之间,其形成早于碱性岩浆,指示碱性岩浆早期为还原环境,晚期趋于氧化。独居石LA-ICP-MS U-Th-Pb结果显示波孜果尔稀土矿化时代约为280Ma,结合前人已获得的锆石U-Pb年龄,表明波孜果尔碱性岩浆活动时间从~290Ma到280Ma,持续了至少10Myr。进一步研究发现,从时间和空间上,波孜果尔含矿碱性岩所在的碱性岩带形成与塔里木地幔柱有关。地幔柱就位诱发被先前俯冲物质交代富集稀有-稀土元素和挥发性成分的岩石圈地幔低程度部分熔融形成富成矿元素的碱性岩母岩浆,随后在岩浆演化晚期富集成矿。  相似文献   

A-type volcanics in Central Eastern Sinai, Egypt     

M.D. Samuel  H.E. Moussa  M.K. Azer   《Journal of African Earth Sciences》2007,47(4-5):203-226

Alkaline rhyolitic and minor trachytic volcanics were erupted 580–530 Ma ago. They occur with their A-type intrusive equivalents in Sinai, southern Negev and southwestern Jordan. At Taba-Nuweiba district, these volcanics outcrop in three areas, namely, Wadi El-Mahash, Wadi Khileifiya and Gebel El-Homra. Mineralogically, they comprise alkali feldspars, iron-rich biotite and arfvedsonite together with rare ferro-eckermannite. Geochemically, the older rhyolitic volcanics are highly evolved, enriched in HFSE including REE and depleted in Ca, Mg, Sr and Eu. The rhyolitic rocks of Wadi El-Mahash and Gebel El-Homra are enriched in K₂O content (5.3–10.1 wt.%) and depleted in Na₂O content (0.08–2.97 wt.%), while the rhyolites of Wadi Khileifiya have normal contents of alkalis. Their REE patterns are uniform, parallel to subparallel, fractionated [(La/Yb)_n = 5.4] and show prominent negative Eu-anomalies. They are classified as alkali rhyolites with minor comendites. The younger volcanics are classified as trachyandesite and quartz trachyte (56.6–62.9 wt.% SiO₂). Both older and younger volcanics represent two separate magmatic suites. The overall mineralogical and chemical characteristics of these volcanics are consistent with within plate tectonic setting. It is suggested that partial melting of crustal rocks yielded the source magma. Lithospheric extension and crustal rupture occurred prior to the eruption of these volcanics. The rather thin continental crust (35 km) as well as the continental upheaval and extensive erosion that preceded their emplacement favoured pressure release and increasing mantle contribution. The volatiles of the upper mantle were important agents for heat transfer, and sufficient for the anatexis of the crustal rocks. A petrogenetic hypothesis is proposed for the genesis of the recorded potassic and ultrapotassic rhyolitic rocks through the action of dissolved volatiles and their accumulation in the uppermost part of the magma chamber.  相似文献