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1.
相山两种不同成因角闪石的地球化学特征对比   总被引：1，自引：0，他引：1  
通过详细研究相山两种不同成因角闪石的元素及同位素地球化学发现：江西相山铀矿田北部同时存在两种不同成因的角闪石：正变质成因的角闪石，寄主岩石为斜长角闪(片)岩，微量元素以富集大离子亲石元素(LILE)(K,Rb，Th，Ta，U)、稍为富集Ti,Se和相对贫高场强元素(HFSE)(Zr，Hf,Y，Yb，Cr，HREE)为特征，稀土总量低，稀土分布型式为近水平型，δ^18O为7．95～8．58，显示变质火成岩的氧同位素特征；副变质成因的角闪石，寄主岩石为含石榴角闪石英片岩．微量元素以高度富集大离子亲石元素(LILE)(K，Rb，Th，U)、稍为富集Ta,Nb，Ce，Zr，Hf，Sm和相对贫高场强元素(HFSE)(Ti，Y，Yb，Cr)、强烈亏损Sc为特征，稀土总量高．轻重稀土相互分离程度高，轻稀土富集，O同位素组成(δ^18O)较高，为9．95～10．02，显示碎屑沉积变质岩的氧同位素特征。  相似文献   

2.
Robert Cullers 《Lithos》1988,21(4):301-314
A series of soil and stream sediments developed during intense weathering on the metaluminous Danburg granite, northeastern Georgia, U.S.A., have been analyzed mineralogically and chemically. The concentrations of Ba, Na, Rb and Cs in the silt and coarser fractions are controlled mainly by feldspars and biotite. Hf is controlled by zircon, and the REE (rare-earth elements) and Th are largely controlled by sphene. Variations in feldspar, sphene and zircon may produce small variations in Eu/Sm and La/Lu ratios. Ferromagnesian minerals control Ta, Fe, Co, Sc and Cr concentrations.

The mineralogical and chemical composition of the Danburg granite is more closely reflected in the silt than in the sand or gravel fractions of stream sediments. In the silt, the contents of Rb, REE, Th, Ta, Fe, Co and Sc and the ratios of La/Sc, Th/Sc, La/Co, Th/Co, Eu/Sm and La/Lu are similar to those in the unweathered granite. In contrast, these element contents or ratios in the sands and gravels are 0.05−3× the concentration in the unweathered granite. Ta and Ba contents are an exception to the above. The Ta and Ba contents of the sands and gravels are similar to those of the granite.

In the kaolinite-halloysite clays, the content of Na is depleted relative to the source. Rb, Cs, Ba, Hf and Ta are depleted or enriched in the clays relative to the source, while the REE, Th, Fe, Co, Sc and Cr are enriched. The Eu/Sm (Eu anomaly size) and La/Lu ratios, and the REE patterns of the clays are similar to those of the source.

Thus, the mineralogy and element contents of a siltstone developed from metaluminous, granitic sources during intense weathering would be expected to be more similar to the source rock than the sandstones and conglomerates. Claystones should contain similar REE patterns and Eu/Sm ratios as the source rock, but such fine-grained sediments might represent much larger areas of source rocks than the more locally derived sandstones or conglomerates.  相似文献   


3.
青海鄂拉山地区陆相火山岩地球化学特征及构造环境   总被引：2，自引：0，他引：2  
鄂拉山岩浆岩带晚三叠世火山岩为中-中酸性火山岩组合,由玄武安山岩、安山岩、英安岩、流纹岩及少量火山碎屑岩等组成,岩石蚀变强烈,成层性差,柱状节理发育,具典型的陆相喷发特点.火山岩属铝饱和类型,里特曼指数(δ)及岩石学等显示具钙碱性特征, (FeO/MgO)、K2 O/Na2O显示可能具有陆缘岛弧环境的特性;轻稀土元素分馏程度高且富集,δEu小于1,为弱负异常,稀土元素配分模式曲线与岛弧型稀土元素配分模式图相似;微量元素Rb、Ba、Th等元素明显富集,而Ti、Y、Yb、Sc、Cr等元素较亏损.Nb/Zr、La/Nb、Th/Ta、Th×Ta/Hf2等特征反映鄂拉山组火山岩产于陆缘火山弧环境.结合区域地质背景、岩石地球化学及构造环境等特征,认为鄂拉山地区晚三叠世火山岩产于大陆碰撞与陆缘弧并存的环境.  相似文献   

4.
采用电感耦合等离子体质谱(ICP-MS)方法对兰坪盆地古近系104件细碎屑岩样品进行了稀土元素及微量元素分析,结果显示∑LEE含量较高,轻稀土含量较富集、重稀土含量较亏损,显示出明显的"右倾"型配分模式。根据稀土元素和微量元素特征、w(Zr)-w(Th)、La-Th-Sc、Th-Sc-Zr/10等多种沉积构造背景判别图解及多种交叉分析方法,对兰坪盆地古近系细碎屑源岩构造背景进行了详细研究。利用La/Th-Hf和La/Yb-∑REE判别图解对兰坪盆地古近系源岩属性进行了分析,结果表明:兰坪盆地古近系碎屑源岩主要以上地壳长英质岩石为主,并混有少量基性岩,反映其物源区构造背景为早期为大陆岛弧构造背景,至晚期逐渐过渡为被动大陆边缘构造背景。  相似文献   

5.
ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅＹｉｎｓｈａｎｄｅｐｏｓｉｔｉｎｔｈｅｎｏｒｔｈｅａｓｔｅｒｎＪｉａｎｇｘｉＰｒｏｖｉｎｃｅｏｆＣｈｉｎａｉｓａｌａｒｇｅ ｓｕｐｅｒｌａｒｇｅｐｏｌｙｍｅｔａｌｌｉｃＣｕ Ｚｎ Ｐｂ Ａｇ Ａｕｄｅ ｐｏｓｉｔ.Ｔｈｏｕｇｈｔｈｅｒｅａｒｅｍａｎｙｄｉｆｆｅｒｅｎｔａｒｇｕｍｅｎｔｓａｂｏｕｔｔｈｅｇｅｎｅｓｅｓｏｆｔｈｅｄｅｐｏｓｉｔ(Ｈａｏ ,1998;Ｚｈａｎｇ ,1997;ＪｉａｎｇｘｉＧｅｏ ｌｏｇｉｃＥｘｐｌｏｒａｔｉｏｎＢｕｒｅａｕ ,1996 ;Ｚｈａｎｇ ,1996 ;Ｈｕａ ,1987;Ｙ…  相似文献   

6.
南秦岭勉县-略阳结合带中超基性岩类主要为方辉橄榄岩和纯橄榄岩,稀土特征为轻稀土亏损,铕富集型;辉绿岩均为轻稀土富集型。变质火山岩可区分为两种组合：一为轻稀土亏损的洋脊拉斑玄武岩,其Ti／V．Th／Ta、Th／Yb、Ta／Yb表明其为MORB型玄武岩,代表本区消失了的洋壳岩石,指示本区晚古生代一早中生代期间的一个古洋盆。另一类为岛弧火山岩组合,除岛弧拉斑玄武岩外,甚至还有大量中、酸性岛弧火山岩,它们并非洋壳的物质组成,而是大陆弧岩浆活动的产物。这表明勉略洋盆在晚古生代-早中生代期间曾经经历过一个较完整的有限洋盆的发生、发展与消亡过程,这期间秦岭已成为一独立的岩石圈微板块,其南缘具有活动大陆边缘的构造属性,秦岭并非华北与扬子陆块之间的简单碰撞产物。  相似文献   

7.
Silicate rock standards AN-G, BHVO-1, QLO-1, RGM-1, SDC-1 and STM-1 have been analyzed for 7 REE (La, Ce, Sm, Eu, Tb, Yb and Lu), Na2O, FeOt, Sc, Co, Cr, Ta, Hf and Th by instrumental neutron activation analysis. The mean values are compared to those from other studies reported in the literature.  相似文献   

8.
Instrumental neutron activation analytical data, for eighteen trace elements (Ba, Co, Cr, Cs, Hf, Rb), Sb, Sc, Ta, Th, La, Ce, Nd, Sm, Eu, Tb, Yb, Lu), Hd2O and Fe203 in eleven French geoche-mical reference samples are presented and discussed briefly.  相似文献   

9.
戚学祥  齐金忠 《现代地质》2006,20(4):555-563
二云花岗片麻岩是组成苏鲁地体南缘超高压变质带朐山杂岩体的重要岩石类型,虽然经历了超高压变质作用,但仍保留了花岗岩的岩石学特征。常量元素和微量元素分析结果表明该片麻岩具有高w(K2O)、低w(CaO)、高w(TFeO)/w(MgO)比值、铝饱和指数偏高的A型花岗岩的特征,岩石类型为高钾碱性过铝质A型花岗岩。稀土元素中轻稀土富集、分馏程度高、Eu强烈亏损,微量元素中Ba、P、Ti、Sc具有明显的负异常,w(Sr)/ w(Y)、w(La)/ w(Yb)和w(Rb)/ w(Sr)、w(Rb)/ w(Ba)较高,尤其是w(TiO2)＜0.2％和w(Y)/ w(Nb)＞1.2的特征,以及在w(Rb)-w(Yb+Ta）和w(Rb)-w(Y+Nb）判别图解上样品投点位于板内环境区等,表明该片麻岩的原岩形成于板内与裂谷有关的非造山环境。锆石SHRIMP U-Pb测年结果揭示其侵位时代为新元古代中晚期((722±32）Ma）,与杂岩体中早期侵位的二长花岗片麻岩及杂岩体上覆地层中的变质火山岩同为Rodinia大陆裂解、扬子地块陆内裂谷形成过程中伴随的岩浆活动的产物。  相似文献   

10.
Instrumental neutron activation analysis was used to determine nine rare earth elements (REE), Sc and five high field‐strength elements (HFSE) in the Multani Mitti (MM) clay. Chondrite‐normalised rare earth element patterns for the MM clay compared with those for the Post‐Archaean Australian Shale (PAAS), Upper Continental Crust (UCC) and North American Shale Composite (NASC) showed enrichment of light REEs and depletion of heavy REEs with a slight negative Eu anomaly. The Multani Mitti clay showed close resemblance to PAAS and NASC in its average REE and HFSE contents. Positive correlations between La/Ce, La/Sm, La/Yb, Zr/Hf, Th/U and Th/Ta ratios predict enrichment of LREEs, Zr and Th and depletion of HREEs. A parent source of felsic origin for the MM clay is also endorsed through the high La/Th and low Th/Sc ratios observed.  相似文献   

11.
<正>Jinshan gold deposit is located in northeastern Jiangxi,South China,which is related to the ductile shear zone.It has a gold reserve of more than 200 tons,with 80%of gold occurring in pyrite. The LREE of gold-bearing pyrite is as higher as 171.664 ppm on average,with relatively higher light rare earth elements(LREE;159.556 ppm) and lower HREE(12.108 ppm).TheΣLREE/ΣHREE ratio is 12.612 and(La/Yb)_N is 11.765.These indicate that pyrite is rich in LREE.The(La/Sm)_N ratio is 3.758 and that of(Gd/Yb)_N is 1.695.These are obvious LREE fractionations.The rare earth element(REE) distribution patterns show obvious Eu anomaly with averageδEu values of 0.664,andδCe anomalies of 1.044.REE characteristics are similar to those of wall rocks(regional metamorphic rocks),but different from those of the Dexing granodiorite porphyry and Damaoshan biotite granite.These features indicate that the ore-forming materials in the Jinshan gold deposit derived from the wall rocks, and the ore-forming fluids derived from metamorphic water.The Co/Ni ratio(average value 0.38) of pyrite suggests that the Jinshan gold deposit formed under a medium-low temperature.It is inferred from the values of high-field strength elements,LREE,Hf/Sm,Nb/La,and Th/La of the pyrite that the ore-forming fluids of the Jinshan gold deposit derived from metamorphic water with ClF.  相似文献   

12.
白石头泉含黄玉的天河石花岗岩体Rb-Sr等时线年龄209.6±9.6 Ma，从下至上可分为5个连续过渡的岩相带，即淡色花岗岩（a带），含天河石花岗岩（b带），天河石花岗岩（c带），含黄玉天河石花岗岩（d带）以及黄玉钠长花岗岩（e带）。岩体的岩石地球化学特征是高F（> 2 %）、高 Rb (500×10-6～1 087×10-6)，低 P2O5 (≤0.06%)，Na2O>K2O，弱过铝 (A/NKC=1.00~1.11)、翼型稀土元素配分曲线 (ΣREE=28.6×10-6~231.9×10-6)、低(La/Lu)N值 (0.11~0.68)、强烈Eu负异常(Eu/Eu* = 0.0005~0.0110)、Nd同位素富集（εNd (t )= -4.4~-4.9）。该岩体的岩浆是中地壳云母片麻岩部分熔融的产物。从a带到e带的地球化学变化是：（1）F，A2O3和Na2O含量逐渐增加，而SiO2，（Fe2O3+FeO+MgO+MnO）、FeO和K2O含量逐渐减少，在标准矿物的Qz-Ab-Or图上总体向Ab角顶移动；（2）总体而言，Cr，Ni，Co，V，W，Nb，Zr，U，Th和Y含量逐渐减少，而F，Li，Rb，Hf，Ta，Sn，Sc，Ga和Zn含量逐渐增加，但d带到e带间存在Li，Rb，Sn，Sc和Zn含量的突降；（3）K/Rb，Al/Ga，Nb/Ta和Zr/Hf值下降， 但K/Cs，Th/U，(La/Lu)N值上升；（4）全岩的δ18O 值从a带的9.25 ‰~9.75 ‰降低到e带的7.32 ‰，d带与e带间存在2.1‰的δ18O值突降。岩浆从a带到e带的垂向分带是分离结晶和流体输运的共同结果。岩体的d带与e带存在明显的成分间断。在矿物成分上表现为黄玉、钠长石和白云母的剧增，钾长石和天河石的剧减。在主量元素上表现为 Na2O和CaO含量的剧增，SiO2和K2O含量的剧减。在微量元素上表现为F，Ga，Sr和Ba含量的剧增，Li，Rb，Sc，Zn和Sn含量的剧减。在稀土元素上，Eu/Eu*和(La/Lu)N值增加，而ΣREE值降低。在氧同位素特征上，δ18O值显著降低。这种间断不仅受分离结晶和流体输运的制约，也与天水加入、围岩混染和亚固相线淋滤有关。  相似文献   

13.
The processes of ultrametamorphism in the juncture zone between the Aldan shield and Stanovoi folded area are manifested in granitization (volume-for-volume replacement of gneisses by trondhjemite gneisses Lc1) and subsequent migmatization with formation of several leucosome generations Lc2, Lc3, Lc4, and Lc5, which is confirmed by U-Pb zircon dating. It was established that the granitization stage is marked by the input of Si, Na, and Ba and removal of practically all major (including K) and minor elements. Formation of migmatite leucosomes is accompanied by further depletion in transition (Ti, Mg, Fe, V, Cr, Ni) and light rare-earth (La, Ce, Nd, and Eu) elements, and accumulation of HFSE (Pb, U, Th, Nb, Ta, Y) as well as medium and heavy rare-earth elements (Sm, Gd, Yb, Lu). Leucosomes Lc4, in addition, are enriched in K, Rb, and especially HREE due to the appearance of garnet, while Lc5 leucosomes become higher in K, Sr, and Pb. The study of relations of trondhjemite gneisses and migmatite leucosomes with protolith, geochemical features, and opposite trends in variations of Zr/Hf, Zr/Nb, Nb/La, and Eu/Eu*, and LREE/HREE ratios in the series of granitization and migmatization indicate that the trondhjemite gneisses were formed during deep-fluid-assisted infiltration granitization under the amphibolite facies conditions, while migmatite leucosomes were generated during evolving anatexis under conditions of subsequent diatexis and continuing fluid reworking. With time, the composition of the fluid changed changed, the role of K increased, and leucosomes acquired granitic composition. Unlike common K and K-Na types of ultrametamorphism, the considered juncture zone is characterized by specific type of ultrametamorphism-Na type, with formation of granitic leucosomes in subordinate amounts at the final stages.  相似文献   

14.
The sediments from three stratigraphic levels in the Bababudan schist belt of Dharwar craton exhibit great diversity in major, trace and rare earth element (REE) geochemistry and thus interpreted to represent significant compositional variation in the source rocks. Detailed geological and geochemical studies have been carried out on clastic rocks constituting the Archaean Sargur supracrustals and the Bababudan belt of Dharwar craton (DC), southern India for understanding the geochemical characteristics and to define the Archaean-Proterozoic Boundary (APB/QPC) in southern India. There is significant contrast in the geochemical signatures for the sediments from these stratigraphic levles. The Sargur enclave population is characterised by slight LREE enrichment with (La/Sm)N ranging from 1.45 to 3.58, almost flat HREE with (Gd/Yb)N ranging from 0.65 to 1.29 with Eu/Eu* ranging from 0.49 to 0.91 suggesting mafic-ultramafic source rocks in the provenance. On the other hand, the Post QPC (PQPC) rocks are characterised by LREE enrichment with (La/Sm)N ranging from 2.66 to 7.07, nearly flat HREE with (Gd/Yb)N ranging from 0.58 to 0.95 and significant depletion of Eu with Eu/Eu* ranging from 0.34 to 0.85, indicating felsic province in the source area. The conglomerates and quartzites representing the QPC are showing mixed nature of these, reflecting the transitional character in depositional environment. Increase in abundance of REE, K2O/Na2O, Th/Sc, La/Sc, Th/U, Hf/Ta and Zr/Y ratios are characteristic of the QPC. The PQPC sediments are enriched in Th, U and HFSE like Hf, Nb, Zr and Y, and depleted in Co and Eu than their older counterparts. These geochemical signatures signify the dominance of mafic-ultramafic rocks in the source area for Sargur rocks and the existence of granite-granodiorite for PQPC clastics. Thus, the unconformity related oligomictic quartz pebble conglomerates (QPC) and quartzites at the base of Bababudan Group resembling the QPC of Witswaterand, South Africa signifies that a stable continental crust had already developed in southern India prior to ∼3.0Ga.  相似文献   

15.
广西苍梧社洞钨钼矿是与花岗岩类有关的矿床。矿区主要花岗岩类包括加里东期花岗闪长岩、花岗闪长斑岩和燕山晚期花岗斑岩。加里东期花岗闪长岩、花岗闪长斑岩具有低Si、K,富Na、Al和基性组分特征,属于强过铝质的正常钙碱性系列岩石;稀土总量低,轻重稀土分馏明显,弱负Eu异常(δEu=0.62~0.70);Ti、Nb、Ta亏损,Th、U、Pb、Zr、Hf富集,Rb/Sr平均值为0.78,明显富集W、Cu、Mo,属于I型花岗岩,为陆内造山带碰撞早期挤压背景下岩浆活动的产物,表现为对钨、钼、铜的成矿专属性。燕山晚期花岗斑岩具有高Si、K,贫Na、Ca和基性组分,属于强过铝质的高钾-中钾钙碱性系列岩石;稀土总量高,轻重稀土分馏不明显,强负Eu异常(δEu=0.03~0.06);Ti、Ba、K、Eu亏损,Th、U、Sm、Dy、Y、Ho、Yb、Lu富集程度更高,Rb/Sr平均值为7.56,明显富集Sn、Bi,属于燕山晚期岩浆演化程度较高的S型花岗岩,为碰撞后伸展环境的板内花岗岩,表现为对锡、金的成矿专属性。  相似文献   

16.
索伦地区玛尼吐组火山岩岩相学鉴定为安山岩、粗安岩和英安岩,化学成分显示以玄武粗面安山岩、粗安岩为主,少量流纹岩。LA-ICPMS锆石U-Pb定年结果显示其形成于130~132 Ma之间的早白垩世。地球化学特点上主要属高钾钙碱性系列。稀土总量较高(95.19~198.38)×10~(-6),轻重稀土分馏较明显(LREE/HREE=6.38~10.59),弱的负铕异常(δEu=0.68~1.01),富集大离子亲石元素(K、Rb、Th)和轻稀土元素,亏损高场强元素(Nb、Ta、P、Ti)。微量元素具高Sr(多499×10~(-6))和低Yb(最大值为2.83×10~(-6)3.6×10~(-6))、Y(多29.9×10~(-6))和高Sr/Y和低Rb/Sr比值,显示了弧火山岩的特征。正的ε_(Hf)(t)值(7.3~13.7),锆石~(176)Hf/~(177)Hf平均值为0.282964,显示玛尼吐组安山质岩浆源区主要为岩石圈地幔和新增生下地壳的部分熔融,且岩浆形成的过程中受到了流体的改造作用。玛尼吐组火山岩形成于岛弧构造环境,该岛弧构造背景的产生可能与受古太平洋板块俯冲作用有关。  相似文献   

17.
满洲里南部白音高老组流纹岩锆石U-Pb定年及岩石成因   总被引：12，自引：3，他引：9  
满洲里南部白音高老组火山岩主要由流纹岩组成,含少量珍珠岩和流纹质凝灰岩。LA-ICPMS锆石U-Pb定年结果显示,流纹岩形成于141~139Ma的早白垩世早期。岩石地球化学研究表明,火山岩具有高硅富碱、贫钙镁和高FeOT/MgO比值的特征; 稀土丰度总量较高(∑REE介于103×10-6~488×10-6),轻重稀土分馏明显［(La/ Yb)N=4.12~30.94)］,Eu负异常显著(δEu=0.12~0.46); 微量元素以富集Rb、Th、U、K,强烈亏损Ba、Sr、P、Ti,中等亏损Nb、Ta和高Ga/Al值为特征,与A-型花岗岩特征相似。锆石176Hf/177Hf比值介于0.282785~0.282970之间,εHf(t)值均为正值,介于3.78~9.98之间。流纹岩岩浆来源于斜长石稳定区玄武质下地壳物质的部分熔融,形成于非造山板内伸展构造环境。  相似文献   

18.
Rb‐Sr and K‐Ar age determinations agree with palaeobotanical evidence in assigning an age of 270 Ma (Lower Permian) to the Nychum Volcanics, North Queensland. Geological and geochemical evidence (moderate ‐REE, La/Yb, Th, Zr/Y, Hf/Yb, Sc/Ni) indicate that the volcanics were erupted on a thin, active continental margin. Five magma groups are present: high‐alumina basalts, andesite‐dacites, acid rocks, tholeiitic andesites, and pitchstone with a high La/Yb ratio. The high‐alumina basalts and calc‐alkaline andesites have a parent‐daughter (source rock‐partial melt) relationship. The acid rocks share high HREE, Zr, Hf, Zn, Sc, Fe/Mg and low Al with, and may be fractionated from, the tholeiitic subduction‐zone andesites. Low‐pressure fractional crystallisation is evident in all five magma groups.  相似文献   

19.
Abstract Migmatites in the Quetico Metasedimentary Belt contain two types of leucosome: (1) Layer-parallel leucosomes that grew during deformation and prograde metamorphism. These are enriched in SiO2, Sr, and Eu, but depleted in TiO2, Fe2O3, MgO, Cs, Rb, REE, Sc, Th, Zr, and Hf relative to the Quetico metasediments. (2) Discordant leucosomes that formed after the regional folding events when metamorphic temperatures were at their peak. These are enriched in Rb, Ba, Sr and Eu, but display a wide range of LREE, Th, Zr, and Hf contents relative to the Quetico metasediments.
Layer-parallel leucosomes formed by a subsolidus process termed tectonic segregation. This stress-induced mass transfer process began when the Quetico sediments were deformed during burial, and continued whilst the rocks were both stressed and heterogeneous. Subsolidus leucosome compositions are consistent with the mobilization of quartz and feldspar from the host rocks by pressure solution. The discordant leucosomes formed by partial melting of the Quetico metasediments, possibly during uplift of the belt. The range of composition displayed by the anatectic leucosomes arises from crystal fractionation during leucosome emplacement. Some anatectic leucosomes preserve primary melt compositions and have smooth REE patterns, but those with negative Eu anomalies represent fractionated melts, and others with positive Eu anomalies represent accumulations of feldspar plus trapped melt.  相似文献   

20.
Geochemical and isotopic data were used for a comparative analysis of Late Mesozoic (150–120 Ma) granitoids in various geological structures of the upper Amur area. The granitoids are metaluminous high-potassic I-type rocks of the magnetite series. They have variable alkalinity and consist of the monzonite-granite and granosyenite-granite associations. The monzonite-granite association consists of calc-alkaline granitoids of normal alkalinity belonging to the Umlekan-Ogodzhinskaya volcanic-plutonic zone and the Tynda-Bakaran Complex of the Stanovoy terrane. The rocks are characterized by negative anomalies of U, Ta, Nd, Hf, and Ti (in patterns normalized to the primitive mantle), with Eu anomalies pronounced weakly in the granodiorites and quartz and monzodiorites and more clearly in the granites: Eu/Eu* = 0.37–0.95, and (La/Yb)n = 7–24, Tbn/Ybn = 1.4–3.2. The granosyenite-granite association comprises of moderately alkaline rocks, which are subdivided into three groups according to their geochemistry. The first group consists of phase-I granosyenites of the Uskalinskii Massif of the Umlekan-Ogodzhinskaya zone with the highest concentrations of Sc, V, Cr, Co, Ni, Cu, Cs, Rb, Sr, Y, Zr, Yb, and Th; negative anomalies at Ba, Ta, Sr, and Hf; Eu/Eu* = 0.50–0.58, (La/Yb)n = 15–16, and Tbn/Ybn = 1.8. The second group comprises of moderately alkaline granitoids of the Umlekan-Ogodzhinskaya zone and the Khaiktinskii Complex of the Baikal-Vitim superterrane. Geochemically, the granitoids of this group are generally similar to the monzodiorite-granite association and differ from it in having lower concentrations of REE and Y, Eu/Eu* = 6.2–1.0, (La/Yb)n = 28–63, and Tbn/Ybn = 2.1–4.5. The third group consists of granitoids of the Chubachinskii Complex of the Stanovoi terrane, which typically show negative Cs, Rb, Th, U, Ta, Hf, and Ti anomalies; the lowest concentrations of V, Cr, Co, and Ni; and the highest contents of Sr. The granosyenites of the first phase display clearly pronounced negative Eu anomalies (Eu/Eu* = 0.53–0.68), (La/Yb)n = 7–24, and Tbn/Ybn = 0.8–2.0. The granitoids of the second phase have (La/Yb)n = 51–84, no Eu anomalies, or very weak Eu anomalies (Eu/Eu* = 0.97–1.23). The silica-oversaturated leucogranites of the third phase are characterized by elevated concentrations of REE, clearly pronounced Eu anomalies (Eu/Eu* = 0.48), and flat REE patterns (Tbn/Ybn = 1.3). The diversity of the granitoids is demonstrated to have been caused largely by the composition of the Precambrian source, which was isotopically heterogeneous. The rocks of the monzodiorite-granite association and first-group granosyenites of the granosyenite-granite association of the Tynda-Bakaran Complex were supposedly derived from garnet-bearing biotite amphibolites. In contrast to these rocks, the source of the second-group granites of the granosyenite-granite association was of mixed amphibolite-metagraywacke composition. The third-group of granitoids were melted out of Early Proterozoic crustal feldspar-rich granulites of variable basicity, with minor amounts of Archean crustal material. The granitoids were emplaced in a collisional environment, perhaps, during the collision of the Amur superterrane and Siberian craton. This makes it possible to consider these rocks as components of a single continental volcanic-plutonic belt. Original Russian Text ? V.E. Strikha, 2006, published in Geokhimiya, 2006, No. 8, pp. 855–872.  相似文献   

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