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1.
藏南洛扎地区淡色花岗岩锆石U-Pb年龄、Hf同位素、地球化学与岩石成因 总被引：3，自引：1，他引：2
洛扎岩体位于高喜马拉雅淡色花岗岩带的东部,锆石U-Pb测年显示其形成年龄为17.7Ma。洛扎岩体的岩性主要为电气石二云母花岗岩和电气石白云母花岗岩,岩石富硅(SiO2为73%~75%)、富钾(K2O为3.9%~4.9%),强过铝(Al2O3为14.5%~15.5%,A/CNK大于1.1),属于高钾钙碱性系列的强过铝淡色花岗岩。岩石具有明显的轻重稀土分异和Eu负异常(Eu/Eu*=0.57),强烈富集大离子亲石元素,相对亏损高场强元素。岩石具有高Rb/Sr(>4)、低CaO/Na2O (0.19~0.26)的特征,指示了其源岩为泥质岩石。(87Sr/86Sr)t和εNd(t)值的变化范围分别为0.725802~0.727276和-13.4~-12.9; 锆石的εHf(t)变化范围为-13.9~-7.5,其较大的变化范围暗示了洛扎淡色花岗岩源区具有不均一性。洛扎岩体可能的构造-岩石成因是,藏南拆离系的启动使深部减压,致使变泥质岩中的白云母发生脱水熔融而形成淡色花岗岩岩浆。岩浆通过STDS所形成的构造薄弱带上侵,沿STDS主拆离断层分布。所以洛扎淡色花岗岩形成于STDS启动所引起的地壳伸展、快速隆起背景下,构造减压所导致的变质岩中白云母的脱水熔融。 相似文献
2.
北秦岭太白山晚中生代正长花岗岩成因及其地质意义 总被引：1，自引：1，他引：0
本文对北秦岭中段太白岩体北部正长花岗岩进行了系统研究.结果表明,岩石为高钾钙碱性I型花岗岩,SiO2=68.49%~72.84%,富Al2O3(14.13%~16.48%),相对富K2O,K2O/Na2O=0.45~1.57(多数样品大于1),A/CNK=0.97~1.05,属于准铝质-铝质系列.岩石富集大离子亲石元素(LILE),亏损高场强元素(HFSE),具弱负Eu 异常(δEu=0.58~0.89),高Sr、低Yb/Y.正长花岗岩锶同位素初始比值ISr=0.7053~0.7112,εNd(t)=-18.6~-0.1(平均为-9.2),二阶段模式年龄t2DM值为0.83~2.11Ga,变化较大,显示其源区主要为古老的壳源物质.铅同位素比值206Pb/204Pb=17.492~17.524,207Pb/204Pb=15.470~15.485,208Pb/204Pb=37.750~38.097,与南秦岭基底相近.锆石U-Pb年龄为153.17±0.89Ma和151.0±1.4Ma,形成于晚中生代.太白正长花岗岩源于古老地壳物质的部分熔融,并有年轻幔源组分的参与,形成于挤压向伸展转换的深部动力学背景. 相似文献
3.
越南东北部高平地区静足 (Tinh Túc) 钨锡矿床分布在银山-静足成矿带上,属于中国西南-越东北花岗岩相关的钨锡成矿带的一部分。花岗岩的锆石SIMS U-Pb测年结果为93.9±3.0Ma,地球化学分析结果显示出过铝质S型花岗岩的特点,高硅 (SiO2含量73.5%~74.6%),铝过饱和 (Al2O3含量14.21%~14.88%),高碱 (Na2O+K2O为6.64%~8.47%)、富钾贫钠 (K2O/Na2O>1),同时富集Rb、Th、U、Zr、Hf,亏损Ba、Nb、Sr、Ti、Eu,轻稀土相对富集,呈现明显的负Eu异常。同位素研究表明,样品的87Sr/86Sr初始比值为0.749±0.027,εNd(t) 为-10.71~-10.42。本文依据派洼花岗岩的地球化学特征,结合花岗岩的锆石U-Pb年代学、同位素分析结果,认为派洼花岗岩为燕山期后造山环境中形成的高度分异岩浆结晶的结果。通过与华南西南部矿床相关岩体比较,将静足派洼岩体归入个旧-大厂花岗岩带。并通过与缅甸境内腾冲-毛淡棉花岗岩带岩体特征对比并结合构造环境判别,提出个旧-大厂花岗岩带的形成可能受到太平洋构造域和特提斯构造域的双重影响,但以后者为主。 相似文献
4.
东昆仑野马泉铁矿相关花岗质岩体年代学、地球化学及Hf同位素特征 总被引：13，自引：4，他引：9
野马泉大型铁多金属矿床位于东昆仑造山带祁漫塔格地区,矿区发育大量与铁多金属成矿关系密切的花岗质岩体。LA-ICP-MS锆石U-Pb定年表明北矿带隐伏二长花岗岩、花岗闪长岩年龄分别为393±2Ma、386±1Ma;南矿带斑状石英二长闪长岩、正长花岗岩年龄为219±1Ma、213±1Ma,分别为早-中泥盆世和晚三叠世岩浆活动的产物。早-中泥盆世花岗闪长岩与二长花岗岩均为高钾钙碱性,A/CNK值（0.92~1.01）<1.1,具中等强度的负Eu异常（δEu为0.60~0.81）,明显亏损P、Nb、Ta、Ti、Sr、Ba等,富集LREE、Rb、Th、U、K等,显示了I型花岗岩的特征。晚三叠世斑状石英二长闪长岩含有少量角闪石,A/CNK值（0.88~0.95）<1,轻稀土富集,具中等负Eu异常（δEu为0.49~0.67）,富集Rb、U、Th、K等大离子亲石元素,亏损P、Nb、Ta、Ti、Sr、Ba等,具有I型花岗岩的特征;正长花岗岩高硅（SiO2=77.20%~78.13%）、富碱（K2O+Na2O=7.91%~8.27%）、贫铝（Al2O3=11.71%~12.18%）、贫钙（CaO=0.90%~1.01%）,富集LREE、Y、Zr、Hf、Th、U、Ga等,强烈亏损Ba、Sr、P、Ti、Eu,具强烈的负Eu异常（δEu为0.08~0.13）,显示弱过铝质A型花岗岩的特征。锆石Hf同位素组成表明,早-中二叠世岩体的εHf（t）为-3.3~6.2,晚三叠世岩体的εHf（t）为-6.3~5.5,显示在成岩过程中有地幔组分的参与。综合研究认为,野马泉矿区早-中泥盆世、晚三叠世岩体分别形成于早古生代构造-岩浆旋回的碰撞-后碰撞阶段和晚古生代-早中生代构造-岩浆旋回的碰撞-后碰撞阶段,可能是由地幔底侵古老陆壳,幔源基性岩浆与壳源花岗质岩浆发生不同程度混合作用而生成,壳幔物质交换为区内大规模铁铜铅锌多金属矿化提供大量成矿物质。 相似文献
5.
江西宁冈岩体的形成时代、地球化学特征及其构造意义 总被引：14，自引：1，他引：13
宁岗岩体是湘赣交界部位呈南北向展布的加里东花岗岩带的重要组成部分,它主要由二长花岗岩组成。锆石LA-ICPMS U-Pb年龄为433.8±2.2Ma,属于加里东期岩浆活动产物。虽然宁冈岩体的SiO2含量变化明显(67.46%~74.85%),但它们的ACNK值都大于1.1,钾大于钠(K2O/Na2O=1.36~2.37),CaO/Na2O比值大于0.3,富集Rb、Th、Cs,亏损Nb、Ta、Ba、Sr,LREE富集 (LREE/HREE=5.8~12.2)和Eu亏损相对明显(δEu=0.28~0.61)。同时,它们还具有较低的εNd(t)值(-9.3~-8.6)、较高的(87Sr/86Sr)i值(0.71172~0.71937)和古老的Nd模式年龄(1838~1909Ma)。这些特征表明,宁冈岩体属于典型的壳源型花岗岩,很可能是在华夏古陆残块与扬子地块之间发生陆-陆碰撞拼贴而引发的地壳伸展-减薄的构造背景下, 通过砂质岩石部分熔融的方式形成。 相似文献
6.
塔里木北缘皮羌地区发育大量闪长质-花岗质岩脉以及哈拉峻花岗岩Ⅰ号和Ⅱ号岩体,这些花岗质岩脉和岩体与赋存大型钒钛磁铁矿矿床的皮羌辉长质岩体空间上共生,推测其成因与塔里木地幔柱岩浆上涌有关。闪长质-花岗质岩脉出露在皮羌辉长质岩体的东缘、北缘及南缘,而哈拉峻花岗岩Ⅰ号和Ⅱ号岩体主要出露在辉长质岩体的西部。花岗质岩脉具有高硅(SiO2=64%~74%)、富碱(Na2O+K2O =8%~10%)、富集Rb、Th、U等大离子亲石元素和Nb、Ta、Zr、Hf等高场强元素,(Ga/Al)×104变化于2.85~3.85之间,具有明显Eu、Ba、Sr负异常等特征,类似A型花岗岩。闪长质岩脉具有低硅(SiO2=53%~59%)、低全碱含量(Na2O+K2O=5%~8%)、以及Eu和Ba正异常。哈拉峻花岗岩Ⅰ号和Ⅱ号岩体的地球化学特征与花岗质岩脉相似。闪长质-花岗质岩脉、哈拉峻花岗岩Ⅰ号和Ⅱ号岩体的εNd(t)值范围在-2.9~-0.2之间,与皮羌辉长质岩体的εNd(t)值相近(-1.1~2.1),表明他们来源于类似的地幔源区。我们认为闪长质-花岗质岩脉、哈拉峻花岗岩Ⅰ号和Ⅱ号岩体主要由底侵的镁铁质岩浆分异出的中酸性熔体结晶分异并伴随不同程度的地壳混染形成,皮羌辉长质岩体是镁铁质岩浆浅部侵位的产物。因此~280Ma大量幔源岩浆底侵是塔里木大火成岩省中A型花岗岩形成的必要前提。 相似文献
7.
北秦岭马河钼矿区花岗岩类的锆石U-Pb年龄、地球化学特征及其地质意义 总被引：3，自引：0，他引：3
本文对北秦岭马河钼矿区桃官坪中-细粒二长花岗岩和西沟斑状二长花岗岩进行了LA-ICP-MS锆石U-Pb年龄测定,分别获得了157±1Ma(NSWD=13)和153±1Ma(NSWD=14)的谐和年龄,表明其为晚侏罗世侵入体。马河钼矿的形成与这两个侵入体密切相关,据此限定该钼矿床成矿时代略晚于157~153Ma,为侏罗世晚期成矿。桃官坪和西沟花岗岩具有高硅(68.12%~76.33%),富碱(Na2O+K2O=6.35%~10.38%)的特征,K2O/Na2O变化较大(0.91~1.89),A/CNK在0.85~1.14之间,为准铝质-弱过铝质高钾钙碱性系列。微量元素上富集U、Pb、Hf等高场强元素,亏损Rb、Ba、K、Sr、P等大离子亲石元素。稀土元素配分曲线为轻稀土相对富集的右倾型,多数具有弱的负铕异常(δEu=0.5~0.9),少数样品具有弱正铕异常(δEu=1.05~1.08)。与华北地块南缘与钼矿有关的花岗岩相比,二者均具有高硅、高钾、富碱的特征。但马河钼矿区成矿花岗岩比华北地块南缘的稍基性,这可能是导致马河钼矿的矿床规模比华北地块南缘较小的原因之一。 相似文献
8.
新疆白石头泉高铷氟花岗岩不同相带云母成分及其演化 总被引：1，自引：1，他引：0
白石头泉含黄玉花岗岩体在露头上显示很好的岩性分带,从下至上依次为: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)和黄玉钠长花岗岩(e带).岩体组成矿物主要为石英、钾长石(部分富铷的为天河石)、钠长石、黄玉和云母,副矿物为锰铝榴石和萤石.总体说来,从a带到c带,云母的Al、Mn、F和Rb含量递增,Fe、Mg和Ti含量递减;Li含量从a带到b带和c带递增,但b带和c带之间变化不明显.从c带到e带,随着Fe、Mg和Ti的减少,总体上表现为Al、Li递增,F、Mn和Rb递减的演化方向,但Li、F、Mn和Rb在c带和d带之间变化不明显,d带和e带之间却表现出急剧的变化.e带中的次生云母与原生云母相比,前者F、Li高而Al低,从a带到e带,Na K变化不明显.云母成分的这些变化特征与岩体的演化趋势相一致.白石头泉岩体与世界上其他地方类似花岗岩相比,没有出现锂云母这种高度富锂矿物,这可能与岩体中锂含量较低有关. 相似文献
9.
藏东同普杂岩体年代学、地球化学、Sr-Nd同位素特征及大地构造意义 总被引：1，自引：1，他引：0
同普杂岩体位于藏东江达地区。本文对该杂岩体岩相学、年代学、主微量元素以及Sr-Nd同位素进行了详细的研究。结果表明,该杂岩体主要由石英闪长岩、花岗闪长岩、含黑云母花岗岩和斑状花岗岩4种岩石类型组成,前三者形成时代分别为262.8±1.5Ma、263.9±1.9Ma、263.7±1.6Ma。其中,含黑云母花岗岩与斑状花岗岩呈渐变过渡关系,它们和花岗闪长岩一起均具有高SiO2(65.1%~76.6%)、高K2O+Na2O(4.84%~8.13%),低MgO(0.25%~2.28%),低FeOT(0.99%~4.44%),高A/CNK值(除一件样品外两者A/CNK值均大于1.1),以及Ba、Sr、Eu亏损等,均符合强过铝质S型花岗岩的特征。但前两者与后者CaO/Na2O、Rb/Ba、Rb/Sr值均存在明显差异,哈克图解上也不存在线性关系,表明它们源区存在差异。石英闪长岩则具有相对低的SiO2(54.2%~55.4%)、低K2O+Na2O(3.15%~4.72%),高MgO(3.78%~4.79%),高FeOT(6.13%~8.09%)等特征。其还具有明显的Nb负异常,不具有Sr的负异常,以及轻稀土相对富集等,均符合岛弧岩浆岩的特征。Sr-Nd同位素特征显示,斑状花岗岩与花岗闪长岩具有相似的初始Sr比值(分别为0.7099,0.7125)和εNd(t)值(分别为-8.6,-10.3),而石英闪长岩则具有较低的初始Sr比值(0.7062),较高的εNd(t)值(1.37)。前两者均落入研究区S型花岗岩与高硅流纹岩区域,后者落在金沙江MORB的下方。通过综合分析,本文认为同普杂岩体形成于火山弧环境,且各岩石类型具有不同的源区:含黑云母花岗岩、斑状花岗岩与花岗闪长岩的源区分别为古老的泥质变质岩和贫泥质的变质砂岩;石英闪长岩则来自富集地幔。表明在晚二叠世早期(~263Ma)金沙江洋盆仍处于俯冲阶段,江达地区主要受金沙江洋盆俯冲消减体系控制而非地幔柱体系。 相似文献
10.
西秦岭党川地区泥盆纪花岗岩类地质地球化学特征及构造意义 总被引：1，自引：0，他引：1
党川地区位于祁连—北秦岭造山带结合部位,该地区分布有不同时期的花岗岩类,泥盆纪花岗岩类由党川岩体、火炎山岩体2个岩体组成。党川岩体岩石化学以富集SiO2(SiO2=72.29%～73.40%)、K2O(K2O∕Na2O=0.86～2.01)、Al2O3(A ∕ CNK =1.05～1.20)为主要特征;火炎山岩体岩石总体SiO2较低(平均69.70%),但K2O(K2O ∕ Na2O =1.14～1.88) 、Fe2O3+FeO﹑MgO较高。岩体的共同特征是岩石属钾玄质系列,表现为过铝质岩石( A ∕ CNK大于1.0)的特征;微量元素相对富集Ba、Zr、Rb、Sm、Ta及Rb、Ba、Th、Nb等元素;稀土元素丰度总体较高,以富集轻稀土元素,发育明显的铕负异常和铕亏损,δEu值较低(δEu=0.36～0.61)为主要特征;岩石锶初始比n(87Sr）/n(86Sr）i 大于0.7070,氧同位素δ18OSMOW较高(δ18OSMOW=＋8.89‰～＋1108‰),岩体物质来源为上地壳,属浅源的壳源型花岗岩类,具S型花岗岩的特征,其形成与后造山阶段的大陆抬升作用有关。 相似文献
11.
东疆白石头泉含黄玉天河石花岗岩体的地球化学：分带和岩浆演化 总被引：2，自引：0，他引：2
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
12.
The Baishitouquan amazonite and topaz-bearing granite is one of the typical high-rubidium and high-fluorine granites in the
eastern part of the Mid-Tianshan belt. This intrusion is in sharp contact with Mid-Proterozoic schists, gneisses and marbles,
and is composed of four zones transitional from the bottom upwards: leucogranite, amazonite granite, topaz-bearing amazonite
granite and topaz quartz albitite.
The Baishitouquan granite contains highly ordered K-feldspar, Li-rich mica, Mn-rich garnet, α-quartz and low temperature zircon
and is chemically high in Si, K, Na, Al, Li, Rb, Cs and F, and low in Ti, Fe, Ca, Mg, P, Co, Ni, Cr, V, Sr and Ba, with Na2O<K2O. Amazonite from the amazonite granite zone contains 1867 ppm Rb. The F contents of bulk rocks are 3040 and 4597 for the
amazonite granite and topaz-bearing amazonite granite zones, respectively. These two zones have δ18O values of 8.97–9.85‰ (SMOW) and show flat REE distribution patterns with strong Eu depletion. K-Ar and Rb-Sr ages of this
intrusion are 226. 6 Ma and 209. 6 Ma respectively, with an initial87Sr/86Sr ratio of 0.987±0.213.
The Baishitouquan granite is the product of crystallization of a low temperature, and water, rubidium and fluorine-rich magma,
which may have been derived from partial melting of muscovite-rich crustal rocks. Consolidation of this granite involved two
contrasting and successive stages: melt crystallization and hydrothermal metasomatism and precipitation. Various geological
features of this granite were formed during the transition from the magmatic to the hydrothermal stage. 相似文献
13.
Siegesmund S. Steenken A. López de Luchi M. G. Wemmer K. Hoffmann A. Mosch S. 《International Journal of Earth Sciences》2004,93(1):23-43
Within the southern part of the Sierra Pampeanas (the Sierra de San Luis, Argentina), a series of extensive intrusive bodies are regarded to post-date the Famatinian cycle but were emplaced during the Achalian, a period of heterogeneous deformation along crustal scale fault zones. The largest of those is the Las Chacras-Potrerillos batholith that is situated at the northern end of the transpressive, sinistral Guzmán shear zone. This composite pluton exhibits three sub-domains that comprise two granitoid sub-units each: The southern Potrerillos stock (muscovite-bearing red granite and biotite-bearing red granite) and the central (biotite porphyritic granite and giant porphyritic granite) and northern domain (equigranular granite and porphyritic granite) of the Las Chacras stock. The crystallisation ages of the biotite porphyritic granite is around 381 Ma (U/Pb on zircons and Pb/Pb on sphene), while the host rock was already cooled below 350 °C at 420 Ma. Thermal modelling approaches favour a pulsed intrusion with a duration of 1.5 Ma. The emplacement was followed by rapid cooling below the muscovite cooling temperature. Biotite cooling ages in different sub-units reflect either a long-lasting cooling history of approximately 30 Ma (which is supported by the modelling) or a reheating effect at around 350 Ma. Devonian-age determinations on the fault rocks and granitoids point to a syn-tectonic emplacement of the batholith. The pluton is interpreted to be positioned at the crossover of sinistral shear zones. The origin of this NNE directed extensional setting in a transpressive regime seems to be related to the transfer of displacement along a secondary set of NNW-trending sinistral faults. The final emplacement is due to a subsequent ballooning of the batholith following the direction of space creation. This model is based on the relative timing of the emplacement sequence and macroscopically visible planar fabrics in the field as well as magnetic fabric data. Our results indicate that the emplacement is syn-kinematic with respect to the Achalian deformation event. 相似文献
14.
Sheila J. Seaman Helle Gylling John P. Hogan Frank Karner G. Christopher Koteas 《Contributions to Mineralogy and Petrology》2011,162(6):1291-1314
The Tunk Lake pluton of coastal Maine, USA is a concentrically zoned granitic body that grades from an outer hypersolvus granite
into subsolvus rapakivi granite, and then into subsolvus non-rapakivi granite, with gradational contacts between these zones.
The pluton is partially surrounded by a zone of basaltic and gabbroic enclaves, interpreted as quenched magmatic droplets
and mushes, respectively, as well as gabbroic xenoliths, all hosted by high-silica granite. The granite is zoned in terms
of mineral assemblage, mineral composition, zircon crystallization temperature, and major and trace element concentration,
from the present-day rim (interpreted as being closer to the base of the chamber) to the core (interpreted as being closer
to the upper portions of the chamber). The ferromagnesian mineral assemblage systematically changes from augite and hornblende
with augite cores in the outermost hypersolvus granite to hornblende, to hornblende and biotite, and finally, to biotite only
in the subsolvus granite core of the pluton. Sparse fine-grained basaltic enclaves that are most common in the outermost zone
of the pluton suggest that basaltic magma was present in the lower portions of the magma chamber at the same time that the
upper portions of the magma chamber were occupied by a granitic crystal mush. However, the slight variations in initial Nd
isotopic ratio in granites from different zones of the pluton suggest that contamination of the granitic melt by basaltic
melt played little role in generating the compositional gradation of the pluton. The zone of basaltic and gabbroic chilled
magmatic enclaves, and gabbroic xenoliths, hosted by high-silica granite, that partially surround the pluton is interpreted
as mafic layers at the base of the pluton that were disrupted by invading late-stage high-silica magma. These mafic layers
are likely to have consisted of basaltic lava layers and basalt that chilled against granitic magma to produce coarse-grained
gabbroic mush. Basaltic and gabbroic magmatic enclaves and gabbroic xenoliths are hornblende-bearing, suggesting that their
parent melts were relatively hydrous. The water-rich nature of the underplating mafic magmas may have prevented extensive
invasion of the granitic magma by these magmas, owing to the much greater viscosity of the granitic magma than the mafic magmas
in the temperature range over which magma interaction could have occurred. 相似文献
15.
16.
A. J. Tullocb 《矿床地质》1986,5(3):27-36
The 'S' type Barrytown biotite granite pluton which intrades Lower Ordovician greywacke and shales is exposed noar jts original roof level. The pluton is intemally zoned from a biotite-rich margin to an acid core. Mild pervasive hydrothermal alteration which affects much of the pluton comprises 3distinct varietiest; early propylitic alteratiori (chlorite-sericite +clinozoisite, sphene) was concentrated above the NW-SE trending, residially warm pluton core, while later intermediate argillic alteration (kaolinite, illite-tourmaline) developed in the vicinity of roof contacts due to trapping and condensation of acid volatiles. Quartz-tourmaline veins and associated greisen selvedges (quartz-muscovite-rutile in granite, quartz-musccvite-tourmaline in metasediments) are restricted to, and apparently postdate, the central clinozoisite-sphene part of the propylitic zone, and contain minor scheelite and rare wolframite, cassiterite, molybdenite and chalcopyrite. Abundant secondary Ti-phases may have held magmatic Sn, W in situ during alteration of biotite, preventing effective leaching and potential ore concentration. 相似文献
17.
陕西勉县地区关帝坪闪长岩体的LA—ICP—MS锆石U—Pb年龄及其地质意义 总被引：2，自引：0，他引：2
秦岭造山带印支期花岗岩的成因研究是当前秦岭造山带研究的热点问题。通过对出露于陕西勉县地区勉略缝合带中光头山岩体西端的关帝坪黑云母闪长岩锆石LA—ICPMSU-Pb年代学研究,探讨其地质意义。岩石主要由斜长石、角闪石和黑云母组成,蚀变较轻。LA—ICP—MS锆石U—Pb测年得到的加权平均年龄为220．5士3．1Ma（MSWD=0．66,2σ）,代表该闪长岩体的结晶年龄。该年龄与附近的光头山黑云母斜长花岗岩的年龄216±2Ma很接近,由此推断两者应产出于相同的构造背景。结合前人研究结果,推断该黑云母闪长岩体可能为勉略洋闭合后的碰撞后期产物。 相似文献
18.
Contrasting stratified plutons exposed in tilt blocks, Eldorado Mountains, Colorado River Rift, NV, USA 总被引：2，自引：0，他引：2
Roof-to-floor exposures of mid-Miocene plutons in tilt blocks south of Las Vegas, NV, reveal distinct but strongly contrasting magma chamber statigraphy. The Searchlight and Aztec Wash plutons are well-exposed, stratified intrusions that show a similar broad range in composition from 45–75 wt.% SiO2. Homogeneous granites that comprise about one-third of each intrusion are virtually identical in texture and elemental and isotopic chemistry. Mafic rocks that are present in both plutons document basaltic input into felsic magma chambers. Isotopic compositions suggest that mafic magmas were derived from enriched lithospheric mantle with minor crustal contamination, whereas more felsic rocks are hybrids that are either juvenile basaltic magma+crustal melt mixtures or products of anatexis of ancient crust+young (Mesozoic or Miocene?) mafic intraplate.
Despite general similarities, the two plutons differ markedly in dimensions and lithologic stratigraphy. The Searchlight pluton is much thicker (10 vs. 3 km) and has thick quartz monzonite zones at its roof and floor that are absent in the Aztec Wash pluton. Isotopic and elemental data from Searchlight pluton suggest that the upper and lower zones are cogenetic with the granite; we interpret the finer grained, slightly more felsic upper zone to represent a downward migrating solidification front and the lower zone to be cumulate. In contrast, the upper part of the Aztec Wash pluton is granite, and a heterogeneous, mafic-rich injection zone with distinct isotopic chemistry forms the lower two-thirds of the intrusion. Similar mafic rocks are relatively sparse in Searchlight pluton and do not appear to have played a central role in construction of the pluton. Large felsic and composite dikes that attest to repeated recharging and intrachamber magma transfer are common in the Aztec Wash pluton but absent in the Searchlight pluton. Thus, although both intrusions were filled by similar magmas and both developed internal stratification, the two intrusions evolved very differently. The distinctions may be attributable to scale and resulting longevity and/or to subtle differences in tectonic setting. 相似文献
19.
Abstract: Systematic measurements of magnetic susceptibility were carried out at the outcrops of the Uchiyama granitic pluton, Tsushima Islands. The pluton consists of hornblende-biotite granodiorite and biotite granite. It intrudes concordantly along an anticline axis of the Taishu Group in middle Miocene (16. 10. 5 Ma), and crops out in five areas. The results show that the low magnetic susceptibility facies (LM–facies, <100A-10-6 emu/g) always occurs in the peripheral part of the pluton, while the high magnetic susceptibility facies (HM–facies, > 250 A 10-6 emu/g) occupies the core through the medium magnetic susceptibility zone (MM–facies). It is pointed out that the pluton forms a magnetic zoning within a single plutonic body.
Chemical compositions of the granitoids show no conspicuous differences in major elements among the LM–, MM–, and HM–facies. Biotites from the LM–, MM–, and HM-facies also indicate uniform compositions with Fe/(Fe+Mg)=0. 6.
The pluton is principally surrounded by black mudstones of the Lower Formation of the Taishu Group, which is deltaic to shallow sea sediments of the Eocene to early Miocene age, and the carbon contents in them were analyzed. The analyses show that carbon was mostly decomposed and lost in the hornfels zone, while mudstones in the non-hornfels zone usually contain 0. 5 to 0. 7 % C.
From these facts, it is concluded that the magnetically zoned pluton at Tsushima was formed by an external volatile buffer system such as CH4 –CO2 during the solidifying magma process. 相似文献
Chemical compositions of the granitoids show no conspicuous differences in major elements among the LM–, MM–, and HM–facies. Biotites from the LM–, MM–, and HM-facies also indicate uniform compositions with Fe/(Fe+Mg)=0. 6.
The pluton is principally surrounded by black mudstones of the Lower Formation of the Taishu Group, which is deltaic to shallow sea sediments of the Eocene to early Miocene age, and the carbon contents in them were analyzed. The analyses show that carbon was mostly decomposed and lost in the hornfels zone, while mudstones in the non-hornfels zone usually contain 0. 5 to 0. 7 % C.
From these facts, it is concluded that the magnetically zoned pluton at Tsushima was formed by an external volatile buffer system such as CH