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1.
皖南伏川蛇绿岩是江南造山带上出露最完整的蛇绿岩,主要由地幔橄榄岩、堆晶岩、枕状熔岩和少量硅质岩组成.地幔橄榄岩主要是方辉橄榄岩,具有U型的稀土元素配分模式,副矿物尖晶石的Cr#较高(54～60),堆晶岩组合为纯橄岩-易剥橄榄岩-辉长岩(DIG型),这些特征指示伏川蛇绿岩形成于俯冲带之上的构造环境,属SSZ型蛇绿岩.堆晶岩异剥橄榄岩的锆石SHRIMP U-Pb年龄为827±9 Ma(n=12,MSWD=1.4),侵入到方辉橄榄岩中的辉长岩岩脉的锆石SHRIMP U-Pb年龄为848±12 Ma(n=7,MSWD=1.9),说明扬子板块和华夏板块至少在848Ma之前就开始拼合,它们之间的古大洋在新元古代(～850 Ma)之前就已经俯冲削减. 相似文献
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西藏雅鲁藏布江缝合带西段巴尔地幔橄榄岩成因及构造意义 总被引：10，自引：7，他引：3
巴尔蛇绿岩属于雅鲁藏布江缝合带的西延部分,距拉萨约1200km,主要由地幔橄榄岩、少量的橄长堆晶岩和玄武岩组成.地幔橄榄岩主体为合单辉方辉橄榄岩,少量为二辉橄榄岩.根据巴尔蛇绿岩地幔橄榄岩的结构构造特征,将矿物组合划分为3个世代,第一世代残余地幔矿物组合:橄榄石+斜方辉石+单斜辉石;第二世代部分熔融及熔-岩反应矿物组合:橄榄石+斜方辉石+单斜辉石+尖晶石;第三世代地幔交代作用矿物组合,主要为含水矿物角闪石.将3个世代的矿物组合归并为2个演化阶段:第一阶段,包括第一世代和第二世代矿物组合,形成于MOR(mid-ocean ridge)构造环境下的洋脊扩张阶段;第二阶段,为第三世代矿物角闪石,形成于SSZ(super-subduction zone)环境下的俯冲阶段.对比雅鲁藏布江缝合带不同区段蛇绿岩中地幔橄榄岩的特征,发现雅鲁藏布江缝合带存在MOR和SSZ两种类型的蛇绿岩,其中中段的蛇绿岩主要以典型的SSZ型地幔橄榄岩为主,而东、西段则以受到不同程度SSZ环境改造的MOR型地幔橄榄岩为主,认为雅鲁藏布江缝合带蛇绿岩地幔橄榄岩演化分段性的特征,与新特提斯洋沿弧方向上板块活动的动力学机制的不均一有关. 相似文献
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西藏雅鲁藏布江缝合带西段东波蛇绿岩的构造背景特征 总被引：2，自引：0，他引：2
西藏东波蛇绿岩位于雅鲁藏布江缝合带西段,由地幔橄榄岩、辉石岩和辉长岩等组成。地幔橄榄岩主要为方辉橄榄岩、纯橄岩和少量二辉橄榄岩。岩体的边界出露玄武岩和硅质岩等。地幔橄榄岩中有少量辉石岩和辉长岩的脉岩,宽约1 m,走向北西,与岩体的构造线方向基本一致。各岩相岩石地球化学研究结果表明,东波蛇绿岩的岩相存在较大的差异,玄武岩具有与洋岛玄武岩(OIB)相似的地球化学特征,而地幔橄榄岩中辉石岩、辉长岩脉与洋中脊玄武岩(MORB)相似,形成于洋中脊环境,并受后期俯冲流体作用的改造。东波岩体中二辉橄榄岩具有与深海地幔橄榄岩较一致的轻稀土亏损特征,而方辉橄榄岩和纯橄岩的地球化学特征显示出岩体形成于MOR环境,后受到SSZ环境的改造。东波蛇绿岩的岩石地球化学特征显示其洋中脊叠加洋岛的构造背景。 相似文献
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西藏雅鲁藏布江缝合带西段东波蛇绿岩中锆石U-Pb定年及地质意义 总被引：18，自引：15，他引：3
西藏东波蛇绿岩位于雅鲁藏布江缝合带西段,由地幔橄榄岩、辉石岩和辉长岩等组成.地幔橄榄岩主要为方辉橄榄岩、纯橄岩和少量二辉橄榄岩.地幔橄榄岩中有少量辉石岩和辉长岩的脉岩,宽约1m,走向北西与岩体的构造线方向基本一致.辉石岩由90％透辉石(Wo=48、En =46、Fs =6),少量的斜顽辉石(Wo=2、En=82、Fs=16),5％的斜长石(An =90)和透闪石组成.辉长岩主要由透辉石(Wo =47、En=36、Fs=17)、斜长石(An =47)及少量的镁角闪石组成,岩石成分以低K2O和P2O5含量(均＜0.1％)和亏损的LREE模式为特征,显示N-MORB岩石的特征.经LA-ICP-MS锆石U-Pb原位微区测定,获得辉石岩和辉长岩的年龄分别为130±0.5Ma、128±1.1Ma.首次给出了东波蛇绿岩年龄,代表了东波地区新特提斯洋海底扩张的时代. 相似文献
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雅鲁藏布江缝合带西段普兰蛇绿岩中地幔橄榄岩的岩石学研究 总被引：14，自引：10，他引：4
西藏雅鲁藏布江缝合带西段普兰蛇绿岩以出现面积约600余平方千米的特大型地幔橄榄岩体而引人注目.该地幔橄榄岩以方辉橄榄岩为主体,含有少量的二辉橄榄岩和纯橄榄岩,岩体中另有一些橄榄单斜辉石岩、辉长岩和辉绿岩等侵入体.地幔橄榄岩的主要造岩矿物橄榄石的Fo 90～93,其中呈包裹体的橄榄石的Fo略高,斜方辉石为顽火辉石(En 88～90),单斜辉石主要为顽透辉石和透辉石,以低铝(0.48％～3.96％)和高Mg#(91～96)为特征,铬尖晶石的Cr#值为18～69,其中方辉橄榄岩和二辉橄榄岩中的铬尖晶石属富铝型尖晶石,而纯橄岩中为富铬型尖晶石.橄榄单斜辉石岩的橄榄石Fo值一致较低,平均为88.4,斜方辉石En平均87,单斜辉石以透辉石为主,铬尖晶石的Cr#值为45～69.普兰地幔橄榄岩及橄榄单斜辉石岩都具有相似的稀土元素和微量元素配分模式,表现为LREE相对富集,Eu亏损不明显,微量元素中大离子亲石元素含量较低,部分样品高场强元素亏损,另一些则相对富集,显示地幔橄榄岩具有亏损地幔源区特征,但也具有俯冲带流体的交代特征,表明普兰岩体可能经历了MOR和SSZ两种构造环境,该特征与雅鲁藏布江缝合带东段的罗布莎地幔橄榄岩的特征可以对比. 相似文献
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乌兰敖包基性-超基性岩位于阿拉善北缘兴蒙造山带,由方辉橄榄岩、辉绿岩、辉长岩组成。地球化学分析表明:蛇纹石化橄榄岩为地幔橄榄岩,辉绿岩和辉长岩为拉斑玄武岩系列岩石,均具有与N-MORB相似的微量元素特征,但区别于N-MORB,3种岩石共同组成了蛇绿混杂岩。矿物学分析表明蛇纹石化橄榄岩中橄榄石为地幔橄榄岩中镁橄榄石(Fo=91.10~91.81),铬铁矿为铬尖晶石,具有高的Cr~#和Mg~#值分别为61.04~64.44、50.40~56.37)。单斜辉石出现在方辉橄榄岩、辉长岩及辉绿岩中,而斜方辉石只出现在方辉橄榄岩中,其中方辉橄榄岩中单斜辉石为顽透辉石,辉长岩中为普通辉石,而辉长岩中为次透辉石、贫钙普通辉石、普通辉石,斜方辉石均为斜顽辉石。辉长岩U-Pb年龄为344.5±1.5 Ma,表明该蛇绿混杂岩形成于早石炭世。地球化学及矿物学特征表明乌兰敖包蛇绿岩形成于俯冲早期的弧前环境中,属于SSZ型蛇绿岩。蛇绿混杂岩成因提供铬铁矿形成的有利条件,因此应围绕铬铁矿进行找矿工作。 相似文献
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缅甸密支那地区发现侏罗纪的SSZ型蛇绿岩 总被引：11，自引：7，他引：4
本文报道了在缅甸的密支那地区发现的一套侏罗纪SSZ型蛇绿岩和有关的岩石单元。蛇绿岩由地幔橄榄岩、安山玄武岩、淡色辉长岩和辉长岩类、橄榄辉石岩和含长辉石岩类、以及斜长花岗岩组成。锆石的U-Pb定年获得安山玄武岩的形成年龄为166±3Ma、淡色辉长岩177±1Ma、橄榄辉石岩171±2Ma,和斜长花岗岩176±1Ma。安山玄武岩以低K2O(平均0.21%)和中TiO2(0.8%～1.2%)为特征,熔岩的球粒陨石标准化属于近平坦和LREE轻微富集型〔(La/Yb)N变化于1～1.3之间〕。微量元素MORB标准化蛛网图显示,熔岩和其他基性岩的大离子亲石元素Sr,K,Rb和Ba含量明显富集,而高场强元素Nb、Th、Ta、Zr、Ti明显亏损,为典型的SSZ构造背景成因的熔岩特征。87Sr/86Sr(i)比值为0.70367～0.70397,以及εNd(t)为正值(4～5.3),均表明它们的岩浆源区为亏损地幔源区。从空间展布看,密支那蛇绿岩与缅甸东带蛇绿岩应属同一条蛇绿岩带,与我国西藏的雅鲁藏布江缝合带相连。但不同的是,雅鲁藏布江缝合带侏罗纪时(约170Ma)为MOR型蛇绿岩,但密支那侏罗纪出现的是SSZ型蛇绿岩。两者时间如此相近,我们认为用洋内俯冲来解释较为合适。但值得注意的是,也有人将缅甸东带蛇绿岩与西藏北带的班公湖-怒江缝合带相连,并且后者在侏罗纪时也已经出现SSZ型蛇绿岩。因此,有必要进一步开展对密支那蛇绿岩构造背景的研究。 相似文献
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西藏班公湖—怒江缝合带中段蓬湖蛇绿岩中的洋脊型二辉橄榄岩 总被引：1，自引：0，他引：1
蓬湖蛇绿岩产于西藏藏北湖区的蓬湖西侧,属班公湖-怒江缝合带中段白拉拉弄-依拉山亚带。该蛇绿岩主要由地幔橄榄岩、堆晶岩和辉绿岩等组成。其中地幔橄榄岩由方辉橄榄岩和二辉橄榄岩组成。蓬湖二辉橄榄岩的橄榄石Fo值介于88.85～90.33之间、斜方辉石的Al2O3含量范围在4.26%～6.60%。与原始地幔相比,蓬湖二辉橄榄岩岩石有较高的MgO含量和较低的Al2O3、CaO和TiO2等易熔组分含量;稀土元素总量介于1.11×10-6～1.53×10-6之间,明显低于原始地幔值,配分模式为轻稀土轻微亏损。在原始地幔微量元素蛛网图中,蓬湖二辉橄榄岩显示Rb、Zr亏损,U、Ta、Sr强烈富集特征。蓬湖二辉橄榄岩的铂族元素总量介于22.9×10-9～27×10-9之间,PGEs球粒陨石标准化图解显示其为接近原始地幔的"平坦型"。以上特征与深海橄榄岩相似,指示它们可能形成于大洋中脊环境。定量模拟估算表明,蓬湖二辉橄榄岩可能来源于地幔中尖晶石相二辉橄榄岩源区,系经历了约5%～10%的部分熔融残余。蓬湖堆晶岩矿物结晶顺序为橄榄石-单斜辉石-斜长石,其中异剥橄榄岩中的单斜辉石Mg#值介于86.92～89.93之间、橄榄石Fo平均值为84.45,明显不同于MOR型蛇绿岩堆晶岩。蓬湖堆晶岩的矿物组成、岩浆结晶顺序和矿物成分均与俯冲带上SSZ型蛇绿岩形成的堆晶岩类似。以上结果表明,蓬湖二辉橄榄岩形成于大洋脊环境,为尖晶石二辉橄榄岩源区经历了不超过10%部分熔融的残余,后期由于洋内俯冲作用经历了岩石-熔体反应,形成了SSZ型堆晶岩和含较高Cr#值尖晶石的方辉橄榄岩。 相似文献
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藏北羌塘中部果干加年山早古生代堆晶辉长岩的锆石SHRIMP U-Pb年龄——兼论原-古特提斯洋的演化 总被引：13，自引：6，他引：7
位于羌塘中部龙木错-双湖缝合带中的果干加年山早古生代堆晶岩,主要由辉石橄榄岩、堆晶辉石岩、堆晶辉长岩、斜长岩等岩石类型组成.对堆晶辉长岩中锆石的矿物学与年代学研究表明.堆晶辉长岩中发育3种内部结构特征的锆石晶体,锆石Th、U含量和Th/U值揭示了同一岩浆系统中结晶形成的岩浆锆石.获得堆晶辉长岩SHRIMP锆石U-Pb谐和年龄461Ma±7Ma(MSWD=1.3)、431.7Ma±6.9Ma(MSWD=0.54),分别代表了青藏高原中部地区原一古特提斯洋扩张过程中早期(中奥陶世Darriwilian阶晚期)、晚期(早志留世Telychian阶中期)的岩浆作用事件.果干加年山早古生代堆晶岩具有MORB.的特征,代表了龙木错-双湖缝合带中残存的早古生代蛇绿岩,也是青藏高原中南部地区目前为止认知时代最早的原一古特提斯洋壳的残迹.羌塘中部早古生代蛇绿岩的确定及其年代学的约束,使得龙木错-双湖特提斯洋盆的形成时代至少可以追溯到中奥陶世-早志留世,并推论龙木错-双湖缝合带、南羌塘古生代增生楔及其中生代盆地和班公湖-怒江缝合带共同构成了青藏高原特提斯大洋最终消亡的巨型缝合带,晚古生代原-古特提斯洋向南的俯冲消减导致了冈底斯带石炭纪-二叠纪岛孤型火山岩、二叠纪花岗闪长岩和大洋俯冲型榴辉岩的形成. 相似文献
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齐齐加纳克蛇绿混杂岩位于中国新疆西南天山阔克萨彦岭地区,主要由辉石橄榄岩,橄榄辉石岩,橄榄玄武岩,辉长岩,辉绿岩,基性熔岩等组成。它们以一系列构造碎片近东西向产出,断续沿长约5km,宽约500m。本文应用SHRIMP方法对该蛇绿混杂岩中玄武岩中的锆石进行SHRIMP锆石U-Pb测年,获得了399±4Ma的加权平均年龄,说明该蛇绿混杂岩形成于早泥盆世。结合前人的研究成果,我们推测齐齐加纳克蛇绿混杂岩与吉根蛇绿岩残片均为中亚造山带南天山蛇绿岩带的延伸,可能代表了一个多岛窄洋盆演化的产物,为南天山洋北向俯冲及其后的塔里木微板块与哈萨克斯坦-准噶尔板块陆陆碰撞形成的最后缝合带。 相似文献
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一九四九年详查铜陵铜官山鸡冠山区域时,在狮子山铜矿之氧化带内见有橄榄绿色之矿物生於石英脉之晶硐及裂缝内,该脉系穿插於三叠纪石灰岩及闪长岩侵入体之富含柘榴在接触带中,近处有白钨矿及黄铜矿,经室内吹管分析及显微化学试验,知其兼含铜钨,又作简单物理性检定,发浅蓝色萤光,後经陈四箴先生之定量分析,证明其为钨铜钙矿,在中国系初次发现,其成分与智利等处所产相彷,此系次生矿物,大致原生铜矿物受地表氧化时,含铜溶液与白钨矿相遇即可生成。 相似文献
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Summary The variegated sequence at Kallithea, westernmost part of the island of Samos, consists of pure dolomitic marbles, siliceous marbles, calc-silicate rocks and amphibolites. It was formed from a volcano-sedimentary series by a regional metamorphism under amphibolite facies conditions. Assuming a total fluid pressure of 5 kb, temperature may have reached 700°C. In the siliceous marbles, a retrogressive evolution is documented. The intrusion of the Kallithea igneous suite which took place about 10 Ma ago hardly affected the regional metamorphic sequence. The only exception are small veins of wollastonite in a silicate marble. In contrast to the other tectonic units which form the major part of Samos, no traces of high pressure minerals could be detected in the Kallithea metamorphics, suggesting a different geological history. The age and geotectonic position of the variegated sequence is unknown so far.
With 5 Figures
Herrn Professor Dr. Siegfried Matthes zum 70. Geburtstag gewidmet 相似文献
Zusammenfassung Die bunte Serie von Kallithea (westlichster Teil der Insel Samos), bestehend aus reinen Dolomitmarmoren, Silikatmarmoren, Kalksilikatfelsen und Amphiboliten, geht auf eine vuikano-sedimentäre Folge zurück, die durch eine Regionalmetamorphose unter amphibolitfaziellen Bedingungen geprägt wurde. Hierbei dürften Temperaturen um 700°C erreicht worden sein, wenn man einen Gesamtdruck (P fl ) von 5 kb annimmt. In den Silikatmarmoren ist eine Abfolge retrograder Mineralreaktionen dokumentiert. Vor etwa 10 Millionen Jahren intrudierten in die regionalmetamorphe Serie dioritische bis granitische Magmen ohne das Nebengestein kontaktmetamorph zu überprägen. Eine Ausnahme bilden kleine Wollastonitäderchen in einem Silikatmarmor. Im Gegensatz zu den übrigen tektonischen Einheiten, die den größten Teil der Insel aufbauen, lassen sich in den Metamorphiten von Kallithea keine Anzeichen einer Hochdruckmetamorphose nachweisen, was auf eine abweichende geologische Geschichte hindeutet. Alter und geotektonische Stellung der bunten Serie von Kallithea sind bislang noch unbekannt.
With 5 Figures
Herrn Professor Dr. Siegfried Matthes zum 70. Geburtstag gewidmet 相似文献
14.
一九四九年详查铜陵铜官山鸡冠山区域时,在狮子山铜矿之氧化带内见有橄榄绿色之矿物生於石英脉之晶硐及裂缝内,该脉系穿插於三叠纪石灰岩及闪长岩侵入体之富含柘榴在接触带中,近处有白钨矿及黄铜矿,经室内吹管分析及显微化学试验,知其兼含铜钨,又作简单物理性检定,发浅蓝色萤光,後经陈四箴先生之定量分析,证明其为钨铜钙矿,在中国系初次发现,其成分与智利等处所产相彷,此系次生矿物,大致原生铜矿物受地表氧化时,含铜溶液与白钨矿相遇即可生成。 相似文献
15.
Livingstonite is the principal ore mineral in the deposits of the Huitzuco District in the State of Guerrero, Mexico. The ore is found in the lower part of the Morelos Formation, which consists of a thick bed of sedimentary anhydrite containing lenses of dolomite and dolomite breccia. In the unweathered ore practically all the mercury is in the livingstonite, whereas the antimony occurs partly in the livingstonite and partly in stibnite. Native sulfur forms pockets as much as 30 centimeters in diameter in the ore and is also found in gypsum on the surface away from the ore.It appears that the deposition of livingstonite, rather than of the combination of cinnabar and stibnite that is more usual in other districts, was caused by the native sulfur present in considerable quantity scattered through the sedimentary dolomite and anhydrite above, below, and in the ore. Since the formula of livingstonite is actually HgSb4S8 (not HgSb4S7 as was previously supposed), it is not stable in solutions containing only HgS, Sb2S3, Na2S, and H2O. It has been proved by one of us, experimentally, that in order to form livingstonite, the solutions must contain elemental sulfur in addition to HgS, Sb2S3, Na2S, and H2O. In such solutions the solubility of mercuric sulfide is extremely low. However, the problem of transport is overcome if the elemental sulfur is already present in the wall rock. In that case, the reaction of the elemental sulfur with a solution containing mercuric sulfide and antimony sulfide, but not saturated with either, would precipitate livingstonite, as was proved by our experimental work. 相似文献
16.
Umar Hamzah Rahman Yaacup Abdul Rahim Samsudin Mohd Shahid Ayub 《Environmental Geology》2006,49(8):1156-1162
A geophysical study was carried out in the Banting area of Malaysia to delineate groundwater aquifer and marine clay layer
of the alluvial Quaternary deposits of Beruas and Gula Formations. The Beruas Formation is formed by peat and clayey materials
as well as silt and sands, whereas the Gula Formation consists of clay, silt, sand and gravels. Both Formations were deposited
on top of the Carboniferous shale of the Kenny Hill Formation. A 2-D geoelectrical resistivity technique was used. Resistivity
measurement was carried out using an ABEM SAS 4000 Terrameter. The 2-D resistivity data of subsurface material for each survey
line was calculated through inverse modelling and then compared with borehole data. The resistivity images of all the subsurface
material below the survey lines show similar pattern of continuous structure of layering or layers with some lenses with resistivity
ranging from 0.1 to 50 Ωm. The upper layer shows resistivity values ranging from 0.1 to 10 Ωm, representing a clay horizon
with a thickness up to 45 m. The second layer with depth varies from 45 to 70 m below surface and has resistivity values ranging
from 10 to 30 Ωm. Borehole data indicate coarse sand with some gravels for this layer, which is also the groundwater aquifer
in the study area. The lowermost layer at a depth of 70 m below ground level shows resistivity values ranging from 30–50 Ωm
and can be correlated with metasedimentary rocks consisting of shale and metaquartzite. 相似文献
17.
A major landslide event occurred at Pollatomish, County Mayo, Ireland in September 2003, during a period of intense rainfall.
It comprised about 30 significant individual longitudinal planar type slides of peat and weathered rock. Relatively simple
limit state stability analyses, using the method of slices and an infinite slope analysis, were used to model the slide and
it was found that the features observed on site could easily be reproduced. These included confirmation that thin layers of
peat could be stable on steep slopes but the margin of safety reduces rapidly under elevated pore pressure conditions. As
was observed in the field, the analyses suggested the most vulnerable zone was the upper layer of weathered rock but that
slides could occur in the peat if its thickness was appreciable. Careful site characterization is vital in such studies. Here
efforts have been made to understand the effect of fibers on the peat strength and some sensitivity analyes have been performed
to assess the critical engineering parameters of the peat. 相似文献
18.
19.
《地质学报》1937,17(1)
Early in April 1935 the senior writer together with his formercolleague,Prof.T.O.Chu took a party of students of the graduatingclass of the Department of Geology,National Central University to theiron and copper mining region of south-eastern Hupeh.One of thelocalities visited is the celebrated iron deposit of Tayeh now in active 相似文献
20.
K. A. Foland I. Raczek C. M. B. Henderson A. W. Hofmann 《Contributions to Mineralogy and Petrology》1988,98(4):408-416
The Ascutney Mountain complex of eastern Vermont, USA, is a composite epizonal pluton of genetically related gabbro to granite intrusives. Nd isotopic data are reported for mafic rocks, granites, and nearby country rock. The parental mafic magma producing the complex 122 m.y. ago had 87Sr/86Sr=0.7039, 143Nd/144Nd=0.512678 (
Nd=+3.8) and
18O=6.1, indicating a mantle source with time-integrated lithophile element depletion. Uniform initial radiogenic isotope ratios for granites, which are undistinguishable from those for the most primitive gabbro, suggest that the granite magma evolved from the mafic magma without crustal contamination and that the increase in
18O, to about 7.8, is the result of fractional crystallization. Mafic rocks show a large range in initial 143Nd/144Nd ratio, from about 0.51267 to 0.51236 (
Nd= +3.7 to –2.5), which is correlated with elevated 87Sr/86Sr ratios and
18O. These data substantiate the production of mafic lithologies by fractional crystallization of the parental magma accompanied by assimilation of up to about 50% crust. The local country rocks include gneiss and schist and assimilation involved representatives of both rock types. The isotopic and chemical relationships preclude derivation from a single batch of magma undergoing contamination and indicate that a large magma body at depth evolved largely by fractionation with batches of melt issued from this chamber being variably contaminated at higher levels or at the level of emplacement.The Precambrian gneisses of the Chester dome and overlying lower Paleozoic schists have essentially identical Nd isotope systematics which suggest a crustal formation age of about 1.6. b.y. The parental sediments for the schists were apparently derived from a protolith similar to the gneissic basement without appreciable Sm/Nd fractionation. 相似文献