粤北笋洞花岗岩的形成时代、地球化学特征与成因   总被引：25，自引：10，他引：25  

凌洪飞沈渭洲  邓平蒋少涌  高剑峰叶海敏濮巍  谭正中 《岩石学报》2004,20(3):413-424

笋洞花岗岩体是粤北贵东复式花岗岩体的一个重要组成部分。锆石U-Pb年龄为189.1±0.7Ma,是燕山早期岩浆活动产物。该岩体的主要元素显示富硅、富碱、强过铝质和低 CaO/Na_2O比值等特征;微量元素方面,富集Rb,Th,U,Ce,Sm,Y,亏损 Ba,Sr,P,Ti;LREE轻微富集(LREE/HREE=6.6～8.8,(La/Yb)_N=6.44～10.74),Eu亏损明显(δEu=0.14～0.31);它具有低的ε_(Nd)(t)(-11.4～-9.3),高的δ~(18)O(10.2～12.7‰)、(~(87)Sr/~(86)Sr);(0.72949～0.74923)、~(206)Pb/~(204)Pb(18.180～18.488)、~(207)Pb/~(204)Pb(15.655～15.661)和古老的Nd模式年龄(1762～1933Ma)。上述这些特征表明,笋洞岩体属于典型的壳源型花岗岩,是在地壳伸展-减薄的构造背景下,通过以泥质成分为主的古-中元古代变质沉积岩部分熔融的方式形成。  相似文献   

大别山沙村中生代A型花岗岩和基性岩的源区演化关系   总被引：4，自引：5，他引：4  

谢智  郑永飞闫峻　钱卉 《岩石学报》2004,20(5):1175-1184

A型花岗岩的成因虽存在不同的认识模式,但对大别山沙村A型花岗岩的岩石化学和地球化学研究结果表明,其物质源自大陆岩石圈地幔的部分熔融,含有古老地壳信息。结合被侵入基性岩的地球化学和年代学资料,推测大别造山带中生代岩石圈地幔的地球化学性质与下扬子地幔相似。花岗岩中锆石SHRIMP法U-Pb年龄为119.0±3.2Ma,说明其岩浆侵位于早白垩世,与邻近的基性岩侵位时间相近但稍晚。在三叠纪因大陆俯冲碰撞增厚的岩石圈在早白垩世被拉张减薄,含有古老地壳成分的扬子陆下岩石圈地幔及其上覆下地壳发生部分熔融,形成了不同成分的碰撞后岩浆岩。其中部分基性岩浆分异结晶成为辉长岩,而A型花岗岩可能是同一地幔源区物质小比例部分熔融后分异结晶的产物。  相似文献   

广东省红色风化壳地区水土流失严重性的成因分析--以五华县为例   总被引：5，自引：0，他引：5  

尚志海  丘世钧 《地质灾害与环境保护》2004,15(4):15-18

红色风化壳地区是一个典型的水土流失区，水土流失妨碍了区域的可持续发展。本文分析了广东省花岗岩风化壳地区水土流失的成因，主要从岩性土质、气候水文、地形地貌、森林植被、人类活动等方面分别论述了它们对水土流失的影响。最后以广东省五华县为例，分析了其水土流失严重性及治理，以期为以后的水土保持工作的开展提供一定的借鉴。  相似文献   

Late-Stage Mafic Injection and Thermal Rejuvenation of the Vinalhaven Granite, Coastal Maine   总被引：11，自引：0，他引：11  

WIEBE  R. A.; MANON  M. R.; HAWKINS  D. P.; McDONOUGH  W. F. 《Journal of Petrology》2004,45(11):2133-2153

The Vinalhaven intrusive complex consists mainly of coarse-grainedgranite, inward-dipping gabbro–diorite sheets, and a fine-grainedgranite core. Small bodies of porphyry occur throughout thecoarse-grained granite. The largest porphyry body (roughly 0·5km by 2·5 km) occurs with coeval gabbro, hybrid rocks,and minor fine-grained granite in the Vinal Cove complex, whichformed during the waning stages of solidification of the coarse-grainedVinalhaven granite. Porphyry contacts with surrounding coarse-grainedgranite are irregular and gradational. Compositions of wholerocks and minerals in the porphyry and the coarse-grained graniteare nearly identical. Neighboring phenocrysts in the porphyryvary greatly in degree of corrosion and reaction, indicatingthat the porphyry was well stirred. Thermal rejuvenation ofa silicic crystal mush by a basaltic influx can explain thecomposition and texture of the porphyry. Comparable rejuvenationevents have been recognized in recent studies of erupted rocks.Weakly corroded biotite phenocrysts in the porphyry requirethat hydrous interstitial melt existed in the granite duringremelting. Field relations, along with thermal calculations,suggest that cooling and crystallization of coeval mafic magmacould have generated the porphyry by thermal rejuvenation ofgranite crystal-mush containing about 20% melt. Field relationsalso suggest that some of the porphyry matrix may representnew felsic magma that was emplaced during remelting. KEY WORDS: granite; magma chamber; mafic replenishment; rejuvenation  相似文献   

U-Pb Zircon Calendar for Namaquan (Grenville) Crustal Events in the Granulite-facies Terrane of the O'okiep Copper District of South Africa     

CLIFFORD  TOM N.; BARTON  ERIKA S.; STERN  RICHARD A.; DUCHESNE  JEAN-CLAIR 《Journal of Petrology》2004,45(4):669-691

The O'okiep Copper District is underlain by voluminous 1035–1210Ma granite gneiss and granite with remnants of metamorphosedsupracrustal rocks. This assemblage was intruded by the 1030Ma copper-bearing Koperberg Suite that includes jotunite, anorthosite,biotite diorite and hypersthene-bearing rocks ranging from leuconoriteto hypersthenite. New sensitive high-resolution ion microprobeage data demonstrate the presence of 1700–2000 Ma zirconas xenocrysts in all of the intrusive rocks, and as detritalzircon in the metasediments of the Khurisberg Subgroup. Thesedata are consistent with published Sm–Nd model ages ofc. 1700 Ma (T_CHUR) and c. 2000 Ma (T_DM) of many of the intrusivesthat support a major crust-forming event in Eburnian (Hudsonian)times. In addition, U–Th–Pb analyses of zirconsfrom all major rock units define two tectono-magmatic episodesof the Namaquan Orogeny: (1) the O'okiepian Episode (1180–1210Ma), represented by regional granite plutonism, notably theNababeep and Modderfontein Granite Gneisses and the Concordiaand Kweekfontein Granites that accompanied and outlasted (e.g.Kweekfontein Granite) regional tectonism [F₂(D₂)] and granulite-faciesmetamorphism (M₂); (2) the Klondikean Episode (1020–1040Ma), which includes the intrusion of the porphyritic RietbergGranite and of the Koperberg Suite that are devoid of regionalplanar or linear fabrics. Klondikean tectonism (D₃) is reflectedby major east–west-trending open folds [F₃(D_3a)], andby localized east–west-trending near-vertical ductilefolds [‘steep structures’; F₄(D_3b)] whose formationwas broadly coeval with the intrusion of the Koperberg Suite.A regional, largely thermal, amphibolite- to granulite-faciesmetamorphism (M₃) accompanied D₃. This study demonstrates, interalia, that the complete spectrum of rock-types of the KoperbergSuite, together with the Rietberg Granite, was intruded in ashort time-interval (<10 Myr) at c. 1030 Ma, and that therewere lengthy periods of about 150 Myr of tectonic quiescencewithin the Namaquan Orogeny: (1) between the O'okiepian andKlondikean Episodes; (2) from the end of the latter to the formalend of Namaquan Orogenesis 800–850 Ma ago. KEY WORDS: U–Pb, zircon; O'okiep, Namaqualand; granite plutonism; granulite facies; Koperberg Suite; Namaquan (Grenville) Orogeny  相似文献   

A Sequence of Pan-African and Hercynian Events Recorded in Zircons from an Orthogneiss from the Hercynian Belt of Western Central Iberia--an Ion Microprobe U-Pb Study   总被引：1，自引：0，他引：1  

ZECK  H. P.; WINGATE  M. T. D.; POOLEY  G. D.; UGIDOS  J. M. 《Journal of Petrology》2004,45(8):1613-1629

Sensitive high-resolution ion microprobe U–Pb dating showsthat a biotite orthogneiss from the Hercynian belt of westerncentral Iberia contains 1000–300 Ma zircon. Older, 1000–570Ma ages within this range represent inherited, detrital materialamong which four age components may be recognized:  相似文献   

湖北新春花岗岩类锆石SHRIMP年龄:大别山造山带内弱变质—未变质晋宁期花岗岩类的发现     

薛怀民  刘敦一  董树文  简平  刘晓春 《地质学报》2004,78(1)

蕲春花岗质杂岩体包括斑状二长花岗岩和花岗岩两部分,它们之间在化学性质上存在着很大的差异,前者表现为高Al_2O_3(15.73％)、相对高CaO(2.46％)、Na_2O含量明显高于K_2O(Na_2O/K_2O=1.27),尤以强烈亏损重稀土元素和极强的轻、重稀土元素分馏程度[(La/Yb)_N=46.8]为特征而类似于太古宙高Al_2O_3的TTG岩石。而后者则以较低的Al_2O_3含量(14.05％)、贫CaO(0.82％)、K_2O含量明显高于Na_2O(Na_2O/K_2O=0.81)为特征,轻、重稀土元素的分馏程度[(La/Yb)_N=10.89]也较片麻状二长花岗岩中弱得多。两类岩石中锆石的U-PbSHRIMP年龄分别为824.6±17.6 Ma和784±20 Ma,该时代与大别山造山带内花岗片麻岩的原岩形成年龄类似。大别山造山带内弱变质-未变质晋宁期花岗岩的出现表明扬子板块印支期向北俯冲时,该花岗质杂岩处于俯冲板片的后缘,可代表造山带内扬子基底的原地露头。而岩体周围的高压变质杂岩应是折返上来的无根构造岩片,大别山造山带内高压-超高压变质杂岩的出露不是整体性抬升剥蚀的结果。  相似文献   

Relationships between texture and mechanical properties of hybrid rocks from the Jaala–Iitti complex, southeastern Finland     

M. Risnen 《Engineering Geology》2004,74(3-4):197-211

The relationships between petrographical and mechanical properties of rock aggregate raw materials from the hybridised, subvolcanic Jaala–Iitti complex, southeastern Finland, were investigated. Petrography was quantified from polished thin sections with a polarising microscope to determine the modal composition and grain size distribution, and resistance to fragmentation and abrasion were determined. Abundance of fine-grained minerals (especially of hornblende), fine grain size-dominated grain size distribution, uniform spatial dispersion of hornblende crystals, and intense micrographic intergrowth texture with interlocking grain boundaries were found to have the greatest positive influence on the mechanical properties. The results showed the potentiality of hybridised rocks as raw materials for high quality aggregates that can resist fragmentation and abrasion.  相似文献   

K-Ar Ages of Granitic Magmatism and Related Pegmatite Formation at the Umanotani-Shiroyama Mine, Shimane Prefecture, SW Japan and Their Bearings on Cooling History     

Shouji Kihara    Kenichi Hoshino    Makoto Watanabe    Hirotsugu Nishido  Shunso Ishihara 《Resource Geology》2005,55(2):123-129

Abstract. The Umanotani-Shiroyama pegmatite deposits, the largest producer of K-feldspar and quartz in Japan, are of typical granitic pegmatite. Ilmenite-series biotite granite and granite porphyry, hosting the ore deposits, and biotites separated from these rocks yielded K-Ar ages ranging from 89.0 to 81.4 Ma and 95.2 to 93.7 Ma, respectively. Muscovite and K-feldspar separated from the ore zone yielded K-Ar ages with the range of 96.2 to 93.1 Ma and 87.3 to 80.7 Ma, respectively. Muscovites from quartz-muscovite veins in the ore zone and in the granite porphyry yielded K-Ar ages of 90.4 and 76.3 Ma, respectively. K-feldspar is much younger in age than coexisting muscovite. It is noted that the K-Ar ages of biotite separates and the whole-rock ages are identical to those of muscovite and K-feldspar in the ore zone, respectively. These time relations, as well as field occurrence, indicate that the formation of the pegmatite deposits at the Umanotani-Shiroyama mine is closely related in space and time to a series of granitic magmatism of ilmenite-series nature. Using closure temperatures of the K-Ar system for biotite and K-feldspar (microcline), cooling rate of the pegmatite deposits is estimated to be about 82C/m.y. at the beginning, but slowed down to about 15C/m.y. in the later period.  相似文献   

湖南芙蓉锡矿床中萤石的Sr－Nd同位素研究   总被引：2，自引：0，他引：2  

赵葵东  蒋少涌  姜耀辉  凌洪飞 《地球学报》2005,26(Z1):171-173

芙蓉锡矿床是一个新探明的超大型锡矿床，产于湘南的骑田岭花岗岩体中。本次研究测试了该矿床中与锡石硫化物共生的萤石的Sr和Nd同位素组成。各矿脉中萤石的87Sr/86Sr比值并不相同，变化从0.70770～0.71484，反映了成矿流体的初始87Sr/86Sr比值并不均一。萤石的Sm－Nd同位素组成并没有构成很好的等时线，计算的ENd（t）值变化在－6.6～－9.8之间。萤石的Sr－Nd同位素组成并不同于花岗岩，成矿流体中的Sr和Nd有很大一部分来自围岩的碳酸盐岩地层。  相似文献