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1.
海南石碌矿床是以富铁矿为主,并伴生有钴铜等矿产的著名大型矿集区。通过对该矿床控矿地质条件的再认识,并对其成矿物质来源、岩浆活动与成矿的关系、成矿时代进行了讨论,认为铁钴铜等物质来源很可能来自原始火山沉积地层石碌群中,后期区域变质作用和岩浆活动对其形成起重要的改造富集作用,初步定义其为火山-沉积变质+多期热液叠加改造型矿床。该矿床成矿模式概括为:1)新元古代海底火山喷流沉积期,奠定了铁钴铜等成矿物质的基础;2)加里东—海西期的变质改造成矿期,形成了沉积变质型贫矿体;3)印支—燕山早期热液叠加改造富化期,石碌矿床发生了重要的改造富集作用,形成了富铁矿体;4)燕山晚期热液叠加改造富化期,对原来矿体进行改造富集,并形成了脉状、角砾状铁矿体及伴生的铜钴矿体。 相似文献
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[摘 要] IOCG 矿床是近些年来被认知的一种重要矿床类型,因其巨大的经济和理论研究价值受到
国内外矿业界和学术界的重视。海南石碌铁钴铜(金)矿床在构造环境、与岩浆岩的关系、矿体特征、元
素和矿物组合、围岩蚀变等方面与国外典型的IOCG 矿床有相似之处。该矿床处于大陆边缘拉张的裂
谷环境,早期火山沉积岩为成矿提供初始矿源,后期侵入岩对成矿具有重要的改造富集作用,矿体基本
呈层状、似层状及少量脉状产于石碌群第六层中,一般铁矿体在上,钴铜矿体在下,具Fe-Cu-Co( -Au)
多元素组合,铁氧化物主要为赤铁矿,蚀变以透辉石化、透闪石化为主;在成矿时代方面区别于多数产在
元古宙的IOCG 矿床,而是经历了新元古代海相火山喷流沉积阶段、加里东期区域变质阶段、海西-印支
期热液改造阶段和燕山晚期热液改造阶段。文章认为石碌铁钴铜(金)矿床不仅与IOCG 矿床有较多相
似之处,与国内内蒙古白云鄂博铁稀土铌矿床、四川拉拉铜铁金钴钼稀土矿床、新疆乔夏哈拉铁铜金矿
床、云南迤纳厂铁铜稀土矿床和东川稀矿山铁铜矿床等也有相似之处。因此,在中国开展寻找IOCG 矿
床尤其是大型矿床,是很有前景的。 相似文献
3.
白垩纪时期赣杭构造带的伸展作用 总被引：12，自引：0，他引：12
前人研究认为赣杭构造带在晚中生代有两个阶段拉张活动:第一阶段发生于晚侏罗世,造成中酸性-基性火山岩喷发;第二阶段发生于早白垩世晚期,形成断陷红盆带,伴随基性玄武岩喷溢。以白垩纪基性火山岩地球化学和同位素数据为依据,认为两个阶段玄武岩浆喷发均发生于白垩纪时期,但对早期构造-岩浆活动的认识与之不同,且赣江断裂带对这期活动有限制和转换作用。早期((143±1.1)~(139±0.7)Ma)在赣杭带西端没有酸性岩出露,赣江断裂带附近的玄武岩浆来自亏损地幔,没有地壳物质混染,属于碱性玄武岩系列,属于板内拉张作用的产物。晚期(105~98 Ma)的玄武岩浆来自于富集地幔,有俯冲陆壳成分的不均匀混染,岩石属于拉斑玄武岩和碱性橄榄玄武岩系列,玄武岩浆喷发伴随着强烈的区域伸展作用,形成一系列红层盆地。 相似文献
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内蒙古敖汉旗朝吐沟组火山岩LA-ICP-MS锆石U-Pb年龄 总被引：2，自引：0，他引：2
内蒙古赤峰敖汉旗一带的朝吐沟组由变基性岩、变质酸性火山岩夹云母石英片岩组成。采用LA-ICP-MS技术,对朝吐沟组2件变流纹岩样品进行了U-Pb同位素测定,获得的锆石206Pb/238U年龄加权平均值分别为359.4±1.4Ma和360.3±1.4Ma,即晚泥盆世法门期,表明朝吐沟组形成于晚泥盆世,而非前人认为的早石炭世。朝吐沟组火山岩石组合为变玄武岩和变流纹岩,显示出典型的双峰式火山岩特征,揭示该区在晚泥盆世处于伸展构造环境。 相似文献
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通过野外调研和相关地球化学研究,表明出露于阿尔泰造山带南缘富蕴地区喀腊曼哲一带的中泥盆统阿勒泰组火山岩由玄武岩和流纹岩组成,为一套典型的双峰式火山岩组合。其中,玄武岩多变质为钠长阳起片岩、绿帘透闪片岩等,属拉斑玄武岩系列,低SiO2、K2O,高Ti,稀土配分曲线显示轻稀土略富集的平坦型,无明显Eu异常（SEu=0．92～1．08）,富Th、U等,Nb负异常;流纹岩属钙碱性系列,高SiO2,低K2O,为钠质型,稀土配分曲线显示Eu负异（dEu为0．29～0．58）的右倾型,富集Th、U、La、Ce和Hf,亏损Sr、Nb、Ta、Zr、P、Ti。二者地球化学特征存在明显差异,表明酸性火山岩并不是由基性岩浆分离结晶产生,而可能是与基性下地壳经不同程度的部分熔融有关;基性火山岩为经俯冲流体改造的亏损地幔部分熔融的产物。岩石地球化学分析结果虽然显示其兼具洋中脊和岛弧火山岩的地球化学特征,但结合区域地质背景,其可能并不是形成于弧后盆地环境,而是岛弧裂谷的产物,属于成熟岛弧。 相似文献
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Papa Malick Ngom Umberto G. Cordani Wilson Teixeira Valdecir de Assis Janasi 《Arabian Journal of Geosciences》2010,3(1):49-57
The Mako bimodal volcanic belt of the Kédougou–Kéniéba inlier is composed of volcanic basalts and peridotites interbedded by quartzites and limestones intruded by different generations of granitoïds. The early volcanic episode of the belt is constituted of submarine basalts with peridotite similar to those of the oceanic abyssal plains. It is intruded by the Badon Kakadian TTG?granitic batholite dated around 2200 Ma. The second volcanic phase is constituted of basaltic, andesitic, and felsitic flows exhibit structures of aerial volcanic rocks. It is intruded by granites dated between 2160 and 2070 Ma. The general pattern of trace element variation of submarine volcanic rocks is consistent with those of basalts from oceanic plateaus which are the modern equivalent of the Archean greenstones belts. The Nd and Sr isotopic systematics typical of juvenile material indicates that the source of these igneous rocks is derived from a depleted mantle source. These results are consistent with the idea of a major accretion within the West African Craton occurring at about 2.1 Ga and corresponding to an important process of mantle–oceanic lithosphere differentiation. 相似文献
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The Miocene northeast Honshu magmatic arc, Japan, formed at a terrestrial continental margin via a stage of spreading in a back‐arc basin (23–17 Ma) followed by multiple stages of submarine rifting (19–13 Ma). The Kuroko deposits formed during this period, with most forming during the youngest rifting stage. The mode of magma eruption changed from submarine basalt lava flows during back‐arc basin spreading to submarine bimodal basalt lava flows and abundant rhyolitic effusive rocks during the rifting stage. The basalts produced during the stage of back‐arc basin spreading are geochemically similar to mid‐ocean ridge basalt, with a depleted Sr–Nd mantle source, whereas those produced during the rifting stage possess arc signatures with an enriched mantle source. The Nb/Zr ratios of the volcanic rocks show an increase over time, indicating a temporal increase in the fertility of the source. The Nb/Zr ratios are similar in basalts and rhyolites from a given rift zone, whereas the Nd isotopic compositions of the rhyolites are less radiogenic than those of the basalts. These data suggest that the rhyolites were derived from a basaltic magma via crystal fractionation and crustal assimilation. The rhyolites associated with the Kuroko deposits are aphyric and have higher concentrations of incompatible elements than do post‐Kuroko quartz‐phyric rhyolites. These observations suggest that the aphyric rhyolite magma was derived from a relatively deep magma chamber with strong fractional crystallization. Almost all of the Kuroko deposits formed in close temporal relation to the aphyric rhyolite indicating a genetic link between the Kuroko deposits and highly differentiated rhyolitic magma. 相似文献
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中国东南部晚中生代-新生代玄武岩与壳幔作用 总被引：46，自引：2，他引：44
中国东南部的火山活动在早中生代时期仅有很小规模,晚中生代最早的、较大规模的岩浆活动始于中侏罗世早期,至早白垩世是火山岩浆活动的鼎盛期,在近100个Ma的时间内形成了大面积分布的晚中生代火山-侵入岩,而在新生代则以面积较小的玄武岩浆喷出活动为主,局限分布于沿海一带。以晚中生代湘南、赣南和闽西南的近EW向火山岩带和浙、闽沿海地区的近NNE向火山岩带,以及新生代近NNE向火山岩带为研究对象,对这些火山岩的地球化学特征对比研究,结合时空分布,讨论了它们的起源及其与壳幔相互作用的关系,以及它们形成的构造环境,其结果显示,EW向晚中生代火山岩带（180～170Ma）的西段玄武岩独立产出,且明显属碱性系列;而中段和东段玄武岩和流纹岩伴生,其中的玄武岩均为亚碱性系列的拉斑玄武岩。它们形成于板内拉张构造环境,是中国东南部特提斯构造域向太平洋构造域转换、晚中生代大规模岩浆作用的序幕。研究表明,该火山岩带自西向东表现出不同程度的壳幔相互作用,玄武岩在成岩过程中有少量陆壳组分加入。NNE向晚中生代火山岩带（130～90Ma）主要为流纹质岩石,安山岩和玄武岩很少。即使是双峰式火山岩也以酸性岩为主,玄武岩仅占全部火山岩体积的30％以下。其中的玄武岩主要属钙碱性系列,少数属拉斑系列。它们形成于火山弧构造环境,是中国东南部受太平洋构造域影响发生大规模火山岩浆作用的主旋律。其中玄武岩岩浆成分受到了较高程度的陆壳物质混染,同时代的中性火山岩是由底侵的玄武岩岩浆和陆壳物质来源的酸性岩浆发生岩浆混合作用而形成的,反映了强烈的壳幔相互作用。NNE向新生代火山岩带,分布在浙闽沿海,以碱性系列玄武岩为主,均含幔源包体,并受NNE向大陆边缘断裂构造的控制。它们形成于板内裂谷环境,是中国东南沿海由晚中生代火山弧构造环境转换为新生代板内裂谷环境的标志,起源于软流圈地幔,并有EMII岩石圈地幔的混合组分,但基本没有受到陆壳物质的混染。 相似文献
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Neoproterozoic bimodal magmatism in the Cathaysia Block of South China and its tectonic significance
《Precambrian Research》2005,136(1):51-66
SHRIMP U–Pb zircon age, geochemical and Sm–Nd isotopic results are reported for the Mamianshan volcanic rocks in the Cathaysia Block of southeastern South China. The Mamianshan volcanic rocks are bimodal in composition and are dominantly transitional to mildly alkaline basalts and subordinate alkaline rhyolite, with an eruption age of 818 ± 9 Ma. The basaltic samples are characterized by LREE-enriched and “humped” trace element patterns, similar to many alkali basalts in continental rifts. Variable ɛNd(T) values between +3.33 and −4.35 indicate that the primary magma of these basalts was derived from an OIB-like mantle source and underwent fractional crystallization plus crustal contamination. The rhyolitic rocks are highly enriched in Th, Ta, Nb, REE, Zr, Hf and Y and depleted in Sr, P, Eu and Ti, sharing affinity to A1-type granites. Combined with their slightly positive ɛNd(T) values (+0.22 to +0.92), the Mamianshan felsic rocks were most likely generated by partial melting of the regional Paleoproterozoic Mayuan amphibolites. The Mamianshan bimodal volcanic rocks in the Cathaysia Block are coeval with the widespread intraplate magmatism around the Yangtze Block. Our results support the idea that a coherent South China Craton was formed during the ca. 1.0 Ga Sibao orogeny, and it subsequently underwent extensive continental rifting related to mantle plume or superplume activities beneath Rodinia since ca. 825 Ma. 相似文献
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东天山博格达造山带石炭纪火山岩及其形成地质环境 总被引：94，自引：35，他引：59
东天山博格达造山带早、中石炭世海相火山地具有双峰式特征,主要岩性为富钠的玄武岩和流纹岩,其次是英安岩,安山质岩石极少出现。玄武岩的特征是：少数岩石含有实际矿物石英,个别岩石含橄榄石斑晶;辉石主要是透辉石和次透辉石,其成分富含铝（Ａｌ２Ｏ３＝４．１７～５．９９）和钛（ＴｉＯ２＝２．８０～４．７８）;基质中的长石主要是钠－更长石,斑晶中有相当数量的中长石和拉长石;全岩化学成分ＣＩＰＷ计算结果绝大部分含 相似文献
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海南石碌铁矿是我国著名的富铁矿床。由于其复杂的地质特征,矿床的形成机制和富集机理一直存在争议。本文对石碌铁矿的碧玉和铁矿石进行了详细的矿相学和岩相学研究,特别是对肉眼无法识别的微小的碧玉进行了识别和观察。结果发现,碧玉除了在铁矿层的露头中有发育,在微观尺度上,微小的碧玉在铁矿石中也普遍发育,并和铁矿具有密切的共生关系,说明碧玉是石碌矿床重要的组成部分。由于碧玉是一种与火山-热液活动有关的化学沉积产物,因此可以明显地排除铁矿的矿浆喷溢型成因模式和矽卡岩型成因模式观点,表明原始的石碌铁矿是一套化学沉积的Si-Fe建造,从而为矿床的火山-热液沉积模式提供了直接有力的证据。由于Si-Fe质沉积过程有可能直接沉积形成富铁矿,所以石碌矿床的富铁矿是否像前人所提出的由构造去硅作用富集形成,值得进一步研究。 相似文献
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Las Lozas volcanic succession, cropping out in the southwestern Puna, Catamarca province, Argentina, consists of an intracontinental volcanic sequence of Carboniferous age. The lavic members are predominantly rhyolites, and subordinated andesites and basalts. The volcaniclastic layers consist of monomictic and polymictic breccias with structures denoting processes of lava fragmentation. They constitute a bimodal suite, ranging from basalts to high silica rhyolites. A new U–Pb SHRIMP age of 320 ± 2 Ma for a rhyolite allows extending the Mississipian magmatism of the region to the lower Pennsylvanian. Hf data point to juvenile sources of Cryogenian age with no evidence of older reworked crustal contamination. 相似文献
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伊宁地块不是一个之前一贯认为的"均匀地块"或"均一地块",而是以乌孙山-塔勒得近东西向区域性大断裂为界的南、北两大次级构造带("弧-盆"体系)叠加拼贴增生而成,火山岩浆作用为这一新的构造单元划分与建立提供了佐证。南构造带由喀拉峻岛弧带和其北的阿腾套弧后盆地构成,主要发育于晚泥盆世-早石炭世早期,火山岩同位素年龄峰值为355～350Ma,17个年龄平均值为351Ma;北构造带由北而南可再细分出清水河-苏布台弧后盆地→阿吾拉勒叠加岛弧带→特克斯-新源弧前盆地,主要发育于早石炭世中-晚期,同位素年龄峰值集中于345～329Ma,18个火山岩年龄平均值为340Ma。这两个"弧-盆"体系以大哈拉军山组钙碱性火山岩为主体,共生早石炭世海相阿克沙克组弧前及弧后沉积岩组合。大哈拉军山组火山岩主体以岛弧火山岩为主,见有富Nb玄武岩、高镁安山岩等,共生埃达克岩和高分异I型花岗岩等小岩体;在弧后还见有碱性火山岩、碱性球泡流纹岩,共生双峰式火山岩。不仅大哈拉军山组火山岩在各构造相中显著有别,而且共生的阿克沙克组在各构造相中差异极为显著。两大次级构造带具有独立的基底建造史,差异显著的盆地沉积史,独特的火山岩浆史和构造演化史。早晚石炭世之间的鄯善运动使南、北两个次级构造带叠加拼贴,构成统一的伊宁地块,晚石炭世进入统一的陆内构造发展演化阶段,发育以伊什基里克组碱性双峰式火山岩为代表的裂谷火山岩浆建造。 相似文献
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海南岛石炭纪双峰式火山岩及其板块构造背景 总被引：4，自引：2，他引：4
海南岛西部的石炭纪火山岩为一套大洋拉斑玄武岩-流纹斑岩的双峰式火山岩。玄武岩中的不相容元素和稀土元素的丰度和比值,以及稀土分配模式与大陆裂谷的拉斑玄武岩的地球化学特征一致,说明海南岛晚古生代裂谷作用的存在。玄武质岩浆来源于地幔深部,演化程度较低,受下地壳物质混染。流纹质岩浆不是玄武岩浆结晶分异产物,而是受裂谷区高热流影响,由陆壳部分熔融形成。 相似文献
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石碌铁矿床位于海南岛五指山褶皱带西段.矿区内外发育以闪长玢岩脉为主的中基性脉岩.LA-ICP-MS锆石U-Pb定年厘定闪长玢岩脉年龄为248±1 Ma(MSWD=0.4),为早三叠世岩浆活动的产物,与同时代的富碱侵入岩体构成“双峰式”侵入岩.闪长玢岩脉为钾玄质系列,低SiO2(49.18%~55.25%)、高Al2O3(14.36%~16.75%)、FeOt(5.98%~10.07%)和MgO(3.80%~5.43%),富集LILE和LREE,亏损HFSE.Nb/Ta、Zr/Hf和La/Nb比值分别为15.33~17.80、36.00~45.23和2.59~8.62;Pb同位素组成(206Pb/204Pb)t=18.087~18.483,(207Pb/204Pb)t=15.473~15.587,(208Pb/204Pb)t=38.272~38.817.LREE/HFSE和LILE/HFSE比值及Pb同位素组成显示为富集地幔来源,但混染有少量的地壳物质.HFSE判别图解指示闪长玢岩脉形成于大陆边缘弧伸展背景,与晚二叠世印支板块NE向向华南地块俯冲造成的大陆边缘弧局部伸展有关. 相似文献
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海南石碌铁矿独居石的成因类型、化学定年及地质意义 总被引：1，自引：0，他引：1
海南石碌铁矿是我国最大的富赤铁矿矿床,同时伴生有钴、铜等多金属矿产。轴向北西-南东向的复式向斜是石碌铁、钴铜矿体的主要控矿构造,富铁矿和钴铜矿的形成与该褶皱变形及伴随的韧性剪切和高温塑性流动有着密切的关系。为获得该构造变形的年代学信息和证实构造变形对成矿物质的富集影响,本文开展了石碌铁矿近矿围岩—石碌群第六层透辉石透闪石岩中独居石的显微结构观察和电子探针化学Th-U-Pb定年(CHIME法)。显微结构观察发现独居石往往沿岩石面理定向分布,且具典型的球冠结构,表现为围绕独居石核部向外依次出现磷灰石、褐帘石、绿帘石同心环。电子探针分析结果表明这些独居石为Ce-La-Nd磷酸盐[(Ce,La,Nd,Th)PO4],具富钍独居石端元组分。ThO 2含量范围(0.78%~4.61%)、稀土特征以及独居石的产出特征均暗示了其为同构造变质成因。电子探针CHIME化学定年结果表明独居石的年龄变化范围为614~397Ma,并具有两个峰值年龄:即主峰值ca.455Ma和次峰值ca.564Ma。低的ThO 2(0.78%~1.65%),PbO(0.02%~0.04%)和CaO(0.50%~0.97%)含量,以及高的Th/U比值(23.06~53.11)暗示了构成ca.564Ma的独居石是早期剪切变形事件的产物。而在随后剪切变形过程中独居石在低角闪岩相变质条件下以及碱性变质流体诱导下发生了溶解-再沉淀,形成了具ca.455Ma年龄的补丁状成分区。该过程引起了U-Pb体系的局部重置,形成的独居石具有变化较大的ThO 2(0.92%~4.61%)、PbO(0.01%~0.08%)和CaO(0.28%~1.58%)含量范围以及Th/U值(24.83~52.86)。在剪切变形之后,早期变质成因的独居石在绿片岩相退变质作用过程中及富Ca、Fe、Si、Al流体参与的条件下,经不平衡反应形成了磷灰石-褐帘石-绿帘石球冠物,反应机制以独居石和球冠矿物间的元素扩散动力学为主。该反应暗示了REE、Y、Th等元素发生了迁移,并可能引起边部独居石的部分Pb丢失。结合华南的构造演化,年龄谱主峰值455Ma代表了与华南加里东造山运动有关的区域变质和动力变质作用事件年龄,是加里东运动在海南岛的响应;次峰值年龄564Ma对应着冈瓦纳泛非事件,暗示了华南在晚新元古代-早古生代与冈瓦纳大陆具有亲缘性,华南加里东运动引起陆内造山过程可能与冈瓦纳大陆的聚合碰撞事件有关。因此,晚新元古代-早古生代造山事件对海南岛构造演化历史具重要影响。此外,该构造运动使石碌群发生褶皱变形,伴随产生的变质流体使铁、钴铜成矿元素进一步活化和富集,对石碌铁、钴铜矿的富集有着重要影响。 相似文献
20.
Mukul Sharma Asish R. Basu Ronald B. Cole Peter G. DeCelles 《Contributions to Mineralogy and Petrology》1991,109(2):159-172
The early miocene Tecuya volcanic center in the southern San Joaquin basin of California consists of flows and tuffs of basalt and rhyolite that erupted, closely spaced in time, in both submarine and subaerial conditions. The rhyolites are overlain by the basalts and constitute approximately 45% of a total of at least 180 km3 of the Tecuya volcanic rocks. The basalts have
Nd(t) values of +2 to +6 and (87Sr/86Sr)i values between 0.7035 and 0.7052. These rocks show LREE enrichment [(La/Yb)N =2.4–5.5; La=28–150 times chondrite] and higher Th/U, Th/Ta, Rb/Ta, Ba/Ta, Cs/Rb but lower K/Rb ratios than MORB. Combined major- and trace-element, and Sr–Nd isotopic data suggest the involvement of subcontinental lithosphere, depleted upper mantle source (MORB), and local continental crust in the basalt petrogenesis.
Nd(t) values in rhyolites vary from +1.5 to +3.7 while (87Sr/86Sr)i ratios range from 0.7051 to 0.7064. The rhyolites display LREE enrichment [(La/Yb)N=10; La=100 times chondrite] along with a distinct negative Eu anomaly (Eu/Eu*=0.75) and depletion of Ti and P. Mixing relations in (87/86Sr)i –
Nd(t) space among basalts, rhyolites, and local continental crust indicate that the Tecuya rhyolites were produced by assimilation of variable amounts of continental crust by MORB-related magmas and subcontinental lithosphere-derived melts. This conclusion is supported by the synchroneity of Tecuya volcanism at 22 Ma with interaction of a segment of the East Pacific Rise along the southern California margin. The Tecuya volcanic rocks thus provide an example for the generation of rhyolitic melts owing to crustal assimilation by basaltic melts during mid-oceanic ridge-induced magmatism along a continental margin. 相似文献