华南花岗岩风化壳中稀土的存在形态及迁移富集模式

本文从化学形态角度，确立了一个ＲＥ形态分析流程，得出风化壳中ＲＥ化学形态可分为活性态，Ｆｅ，Ａｌ共沉淀态及有机结合态３种，全风化层样品中ＲＥ多数以活性态为主，但平远Ｃ剖面ＲＥ却以有机结合态占大多数，活性态、有机结合态ＲＥ与粘土矿物关系密切，而Ｆｅ，Ａｌ共沉淀态的ＲＥ与粘土矿物关系不大，原岩溶出试验表明，ＲＥ在有机介质中的溶出量一般高于无机介质，ＲＥ最大可能是呈有机无机混配络离子迁移，迁移、富集过程是络合、水解、沉淀和吸附反应同时出现，反应受ｐＨ控制，本文初步建立了花岗岩风化壳中ＲＥ往下迁移、富集的模式。     

藏北羌塘地区岛弧花岗岩和外弧花岗岩

羌塘地区花岗岩类岩体大多数沿羌塘陆块的冈玛错-西亚尔岗岛弧分布。岩石类型有花岗岩、黑云母花岗岩,花岗闪长岩、石英闪长岩、闪长岩等,有的岩体还与酸—基性火山岩伴生。侵入体同位素年龄值为135.3—302Ma,为多期侵入,主要为燕山早期(135.3—186.3Ma),少数为燕山晚期。个别同位素年龄值为74.2和99.6Ma,最早不超过燕山晚期。花岗岩类岩体另一分布区是改则-色哇缝合带北侧。岩石类型较单一,主要是酸性岩类的花岗岩、花岗斑岩、黑云母花岗岩、角闪黑云花岗岩等,几乎不出现中性岩。同位素年龄值为120.9—129.8Ma,为燕山晚期产物。     

SHRIMP zircon U-Pb ages and tectonic implications for Indosinian granitoids of southern Zhuguangshan granitic composite,South China

The large southern Zhuguangshan granitic batholith composite consists of granites with ages varying from the Caledonian through Indosinian to Yanshanian. Based on K-Ar dating data, the ages of the major parts of this composite were previously regarded as Yanshanian. In this study, the SHRIMP zircon U-Pb dating method has been adopted for six plutons, Ledong, Longhuashan, Dawozi, Zhaidi, Baiyun and Jiangnan, in the southern Zhuguangshan composite, in which the four plutons other than Baiyun and Jiangnan were previously regarded as Yanshanian granites. Magmatic zircons from these six plutons, dated by this study, have yielded ages of 239±5 Ma (MSWD = 2.5), 239±5 Ma (MSWD = 2.5), 239±2 Ma (MSWD = 1.7), 239±4 Ma (MSWD = 3.2), 231±2 Ma (MSWD = 0.81) and 231±3 Ma (MSWD = 1.8), respectively. The results indicate that these plutons were formed by early Indosinian magmatism. Geochemical characteristics suggest that these granites were formed in an extensional tectonic environment. Therefore, the Indosinian period granites in the southern Zhuguangshan composite were formed by partial melting of the Paleo-Mesoproterozoic crustal components during the collapse of thickened lithosphere after the collision between the South China and Indosinian plates.     

Structures of mylonitic granites of the Yagan metamorphic core complex on Sino-Mongolian border??implications for its kinematics and chronology

The mylonitic granitic plutons are extended in line-shape (L) and parallel to the regional extensional shear foliation. After being unstrained, the primary shapes of these plutons are also nearly sheet-like (S). Their fabrics are of S-L or L type. Various kinds of shear marks indicate top-to-south shear. The plutons of various stages are different in deformation intensity; however, the foliation and lineation of these rocks have the same shear sense, which suggests progressive ductile shearing. The development mechanisms of the fabrics include magmatic flow, high-temperature solidstate flow and mid-low temperature solid-state flow. All this demonstrates that these plutons are probably early synextensional tectonic plutons. Their structural features and ages suggest that the low- and mid-crustal extensional detachments might have occurred at the early stage of the development of the metamorphic core complex in the early Mesozoic. These deformations are much deeper at levels and much older than those formed at the final formation stage.     

冈底斯南麓花岗岩成因与航磁异常格架的关系

西藏冈底斯南麓是我国重要的一个火山-岩浆弧.自中生代以来,受特提斯演化以及后期陆内汇聚碰撞造山作用的控制,地块广泛发育花岗岩.其中,部分花岗岩具有较强的磁性,造成了航磁异常,它们的展布方式也决定了航磁异常的格架.探求航磁异常与花岗岩的联系对于迅速评价航磁异常、圈定隐伏岩体具有重要的意义.本文首先以多尺度边缘检测为手段对研究区航磁异常格架进行讨论,再以区域花岗岩的主微量元素对花岗岩成因进行讨论.1)东段北东向航磁异常主体是由新生代花岗岩所引起,西段存在北东向和北西向两个航磁异常,分别对应于晚白垩纪、第三纪花岗岩.2)新生代东西两段花岗岩磁性的差异与东西两段造山强度有关系.     

西藏日土白垩纪酸性侵入岩年代学及地球化学特征——对班公湖-怒江中特提斯洋盆闭合时限的制约

以西藏日土县北东地区的小型酸性侵入体为研究对象,结合岩石地球化学分析及锆石年龄测试,探讨岩石的成因类型及构造环境,确定班公湖-怒江中特提斯洋盆闭合的时限。研究区酸性岩体的岩性为黑云二长花岗岩,其主要组分的质量分数分别是:SiO_2为63.89%~77.49%,全碱(K_2O+Na_2O)为8.06%~8.95%,全铁(FeOT)为0.48%~4.37%,Al_2O_3为12.43%~16.17%;大离子亲石元素中Rb、Th、U、K明显富集,但Ba、Sr明显亏损;高场强元素中Nb、Ta、P、Ti明显亏损,而Zr、Hf相对富集;轻稀土元素相对富集、重稀土元素相对亏损,负Eu异常明显(δEu=0.09~0.67,平均为0.47),球粒原始标准化分布模式为向右缓倾的V型,属于A型花岗岩。其LA-ICP-MS锆石206Pb/238 U年龄加权平均值为(117.8±1.2)Ma,属于中生代早白垩世中期。从岩石碰撞后A1型花岗岩特征推测,班公湖-怒江中特提斯洋盆在日土地区的闭合时间应在早白垩世中期。     

华北克拉通北缘典型高锶花岗岩区域锶型矿泉水分布特征及成因

华北克拉通北缘存在大量高锶花岗岩体,但其周边区域锶型矿泉水的赋存情况鲜有研究.首次以都山岩体作为典型高锶花岗岩,通过水文地质调查、水样采集、化验分析等方法,对其周边区域锶型矿泉水的分布和形成机理进行了分析.同时对寿王坟岩体、碾子峪岩体、小寺沟岩体、杨杖子岩体等四处高锶花岗岩体周边区域水体进行调查取样分析,以验证锶型矿泉水的分布规律.研究表明,都山岩体周边区域水体中均含锶元素,且距离岩体越近,水样中锶含量越高,最高达13.81 mg/L,远高于中国一般含锶矿泉水的锶含量,而外围长城系砂岩地层水样中锶含量最低.平面上,孔隙水中锶型矿泉水主要沿北东-南西向断裂带和南部挤压带分布;风化带网状基岩裂隙水和构造基岩裂隙水中锶型矿泉水沿北东-南西向断裂带分布;垂向上,孔隙水、风化带网状基岩裂隙水、构造基岩裂隙水中锶含量依次增加.区内高锶花岗岩为矿泉水形成提供了物源,地下水径流过程中地层中锶的不断溶出是形成高锶型矿泉水的内在机制,垂向三含水层可能存在水力联系,入渗过程中锶含量可能不断累积.深层构造基岩裂隙水水质、水量稳定,锶含量高,极具开发利用价值.其他四处高锶花岗岩体周边区域锶型矿泉水的分布与都山岩体区域呈现类似规律.该研究首次揭露高锶花岗岩区域锶型矿泉水的赋存规律,可为众多高锶花岗岩区域开发利用优质锶型矿泉水资源提供参考借鉴.     

不同含水率断层宏微观破裂与强度折减损伤

为探究深部地区断层花岗岩不同含水率下宏观与微观跨尺度性质研究,对不同含水率花岗岩开展轴压力学试验和扫描电镜SEM试验,探讨含水花岗岩多尺度破裂机制与强度折减损伤关系。研究结果表明：无水状态下花岗岩宏观以剪切破坏为主且破裂面较为平滑,随含水率提高宏观以张拉破坏为主,裂纹路径与主应力方向平行且受载后岩样较为松散;低含水率工况微观整体破裂以沿晶破裂为主,高含水率工况微观破裂结构为沿晶破裂和穿晶破裂的复合型破坏为主;吸水中期峰值强度和弹性模量两指标衰减率约为前期6倍,两指标达到衰减期阈值最大限并呈非线性指数下降,吸水后期两指标衰减率回弹至前期状态;劣化系数随含水率增长而降低,吸水前期水分子起润滑岩石内部矿物作用,中后期阶段水分子发生侵蚀导致强度大幅度折减,生成有较多孔洞分布的微观结构形貌和晶体颜色偏白的伊利石,后期的水分子为进一步软化侵蚀作用。     

江西大岭上钨矿区强过铝质花岗岩中白云母研究

白云母是常见的造岩矿物之一,广泛分布于花岗岩、伟晶岩、云英岩和变质岩中,其形成过程受多种因素制约,具有重要的岩石学意义。选取江西大岭上钨矿区强过铝质花岗岩中的白云母为研究对象,通过偏光显微镜观察和电子探针成分分析,发现大岭上强过铝质花岗岩中存在三种类型的白云母,即原生白云母、交代型白云母和次生白云母;且岩相学特征各异。结合前人对原生与次生白云母的地球化学判别标志以及岩相学特征,认为交代型白云母应归属于原生白云母。大岭上强过铝质花岗岩结晶温度为801~872℃,指示其形成于地壳浅部,压力不大的条件下,且岩浆中水分、An组分(更长石)的存在导致岩浆白云母结晶时深度较浅,只有在聚敛构造环境下才能结晶出原生白云母等条件,推断出大岭上强过铝质花岗岩形成深度可能小于11~15 km。