普朗斑岩型铜矿床成矿元素多重分形特征及其矿化强度指示

成矿元素品位的变化受控于长期地质作用过程,具有较强的非线性特征,定量刻画其变化特征有助于深入理解成矿过程,并为找矿预测提供理论依据。运用多重分形去趋势移动均值（MFDMA） 法,分析云南普朗斑岩型铜矿床4号勘探线钻孔Cu元素品位的多重分形特征及其对矿化强度的指示意义。结果显示：所有钻孔Cu元素品位具有多重分形特征,且不同矿化等级的元素分布存在局部奇异性差异,多重分形强度随矿化强度等级减弱而增加;这些特征指示在钾硅化带—带内侧强矿化钻孔的高品位相对聚集,而带外侧角岩化—青磐岩化带的高品位相对分散;通过数据随机重排技术推测Cu品位多重分形结构奇异性差异是由其分布概率密度和长相关性共同作用引起,后者的作用贡献大于前者。     

基于KronosFlow软件对逆冲推覆带构造-热演化的初探

盆地模拟是含油气盆地勘探评价的重要技术方法之一,然而传统的盆地建模2D模拟技术仅适用于拉张型盆地,使得挤压型盆地横向上的热史重建一直是个难题,从而制约了进一步的油气勘探。目前由法国Beicip-Franlab公司设计的KronosFlow软件突破了传统盆模软件对逆冲推覆带、盐构造和泥底辟等复杂构造的局限性,精确控制了横向和垂向上的构造位移,通过跟踪单个网格连续运动形态、恢复侧向变形量以及与TemisFlow软件无缝衔接,实现了对挤压型盆地埋藏史、热史、生排烃史以及油气运聚史的恢复。以塔里木盆地北缘柯坪逆冲推覆带和库车逆冲推覆带为例,利用KronosFlow软件定量反演了新生代以来的构造-热演化历史,并以实测数据约束并验证挤压环境下盆地模拟结果的有效性。柯坪逆冲推覆带的依木干他乌断层在40~30 Ma再次活动,断层附近志留系—泥盆系的温度大于85 ℃,柯坪塔格断层在15~10 Ma活动,断层附近志留系—泥盆系的温度小于70 ℃,寒武系（烃源岩成熟度为1.3%~1.7%）和奥陶系（烃源岩成熟度为0.7%~1.2%）烃源岩热演化程度高,生烃能力强。库车逆冲推覆带侏罗系北段温度介于50~70 ℃,南段温度介于210~230 ℃,盐构造造成地温异常,其中秋里塔格构造带膏盐岩最厚,降温效果最明显。      

巴音戈壁盆地塔木素铀矿床含矿砂岩成岩作用类型、演化序列及其对铀成矿的约束

勘查和研究发现部分砂岩型铀矿床中不仅有表生氧化流体作用还存在深部流体的参与,这类砂岩型铀矿床蚀变类型多样且成因复杂.塔木素砂岩型铀矿表生流体和深部流体活动都很明显,砂岩普遍固结且后生蚀变类型独特,因此,恢复成岩成矿事件及其演化过程,对揭示铀沉淀富集机理至关重要.本文通过镜下鉴定、电子探针、扫描电镜分析等,系统研究了塔木素矿床含矿砂岩成岩作用特征与后生蚀变矿物生成序列,重塑了成岩成矿事件的演化过程.研究结果显示,塔木素矿床砂岩中压实作用较弱而胶结作用很强,重结晶作用普遍,是造成目的层致密的主要原因,赤铁矿、褐铁矿化、碳酸盐化、石膏化是该地区主要的胶结类型.将该地区的成岩演化划分为沉积-早成岩阶段、早期氧化流体作用阶段、热流体改造阶段和晚期氧化流体弱改造阶段.成岩环境由弱碱性向酸性环境转变的过程中的氧化还原过渡部位是造成铀沉淀的关键,大规模的氧化作用是矿床形成的基础,后期热流体活动对早期形成的低品位铀矿石进行叠加改造,是成矿的关键环节.     

Geochronological and geochemical evidence for a Late Ordovician to Silurian arc-back-arc system in the northern Great Xing'an Range,NE China

The early Paleozoic tectonic evolution of the Xing'an-Mongolian Orogenic Belt is dominated by two oceanic basins on the northwestern and southeastern sides of the Xing'an Block,i.e.,the Xinlin-Xiguitu Ocean and the Nenjiang Ocean.However,the early development of the Nenjiang Ocean remains unclear.Here,we present zircon U-Pb geochronology and whole-rock elemental and Sr-Nd isotopic data on the gabbros in the Xinglong area together with andesitic tuffs and basalts in the Duobaoshan area.LA-ICP-MS zircon U-Pb dating of gabbros and andesitic tuffs yielded crystallization ages of 443-436 Ma and 452-451 Ma,respectively.The Early Silurian Xinglong gabbros show calc-alkaline and E-MORB affinities but they are enriched in LILEs,and depleted in HFSEs,with relatively low U/Th ratios of 0.18-0.36 andεNd(t)values of-1.6 to+0.5.These geochemical features suggest that the gabbros might originate from a mantle wedge modified by pelagic sediment-derived melts,consistent with a back-arc basin setting.By contrast,the andesitic tuffs are characterized by high MgO(>5 wt.%),Cr(138-200 ppm),and Ni(65-110 ppm)contents,and can be termed as high-Mg andesites.Their low Sr/Y ratios of 15.98-17.15 and U/Th values of 0.24-0.25 and moderate(La/Sm)_n values of 3.07-3.26 are similar to those from the Setouchi Volcanic Belt(SW Japan),and are thought to be derived from partial melting of subducted sediments,and subsequent melt-mantle interaction.The Duobaoshan basalts have high Nb(8.44-10.30 ppm)and TiO2 contents(1.17-1.60 wt.%),typical of Nb-enriched basalts.They are slightly younger than regional adakitic rocks and have positiveεNd(t)values of+5.2 to+5.7 and are interpreted to be generated by partial melting of a depleted mantle source metasomatized by earlier adakitic melts.Synthesized with coeval arc-related igneous rocks from the southeastern Xing'an Block,we propose that the Duobaoshan high-Mg andesitic tuffs and Nbenriched basalts are parts of the Late Ordovician and Silurian Sonid Zuoqi-Duobaoshan arc belt,and they were formed by the northwestern subduction of the Nenjiang Ocean.Such a subduction beneath the integrated Xing'an-Erguna Block also gave rise to the East Ujimqin-Xinglong igneous belt in a continental back-arc basin setting.Our new data support an early Paleozoic arc-back-arc model in the northern Great Xing'an Range.     

东昆仑山中段布尔汗布达山地区断裂特征及昆中断裂带南界讨论

布尔汗布达山西南缘属东昆仑造山带腹地,新太古代以来区域构造作用强烈。中二叠世,随着东昆仑地区多岛洋盆依次关闭,研究区形成数条近于平行的EW向深大断裂组合,构成昆中断裂带主体格架。通过研究分析与断裂相关的地形地貌、遥感影像、地球物理、岩石地层、变形变质、断裂结构组成、显微构造等,总结出主要断裂特征,并梳理了区内构造格架,针对尚未统一认识的昆中断裂带南界问题进行探讨,最终认为温冷恩断裂属昆中断裂带南界断裂。研究成果为进一步开展相关地质问题分析提供了依据。     

Geology and mineralization of the Sanshandao supergiant gold deposit (1200 t) in the Jiaodong Peninsula,China: A review

The Jiaodong Peninsula in Shandong Province, China is the world’s third-largest gold metallogenic area, with cumulative proven gold resources exceeding 5000 t. Over the past few years, breakthroughs have been made in deep prospecting at a depth of 500–2000 m, particularly in the Sanshandao area where a huge deep gold orebody was identified. Based on previous studies and the latest prospecting progress achieved by the project team of this study, the following results are summarized. (1) 3D geological modeling results based on deep drilling core data reveal that the Sanshandao gold orefield, which was previously considered to consist of several independent deposits, is a supergiant deposit with gold resources of more than 1200 t (including 470 t under the sea area). The length of the major orebody is nearly 8 km, with a greatest depth of 2312 m below sea level and a maximum length of more than 3 km along their dip direction. (2) Thick gold orebodies in the Sanshandao gold deposit mainly occur in the specific sections of the ore-controlling fault where the fault plane changes from steeply to gently inclined, forming a stepped metallogenic model from shallow to deep level. The reason for this strong structural control on mineralization forms is that when ore-forming fluids migrated along faults, the pressure of fluids greatly fluctuated in fault sections where the fault dip angle changed. Since the solubility of gold in the ore-forming fluid is sensitive to fluid pressure, these sections along the fault plane serve as the target areas for deep prospecting. (3) Thermal uplifting-extensional structures provide thermodynamic conditions, migration pathways, and deposition spaces for gold mineralization. Meanwhile, the changes in mantle properties induced the transformation of the geochemical properties of the lower crust and magmatic rocks. This further led to the reactivation of ore-forming elements, which provided rich materials for gold mineralization. (4) It can be concluded from previous research results that the gold mineralization in the Jiaodong gold deposits occurred at about 120 Ma, which was superimposed by nonferrous metals mineralization at 118–111 Ma. The fluids were dominated by primary mantle water or magmatic water. Metamorphic water occurred in the early stage of the gold mineralization, while the fluid composition was dominated by meteoric water in the late stage. The S, Pb, and Sr isotopic compositions of the ores are similar to those of ore-hosting rocks, indicating that the ore-forming materials mainly derive from crustal materials, with the minor addition of mantle-derived materials. The gold deposits in the Jiaodong Peninsula were formed in an extensional tectonic environment during the transformation of the physical and chemical properties of the lithospheric mantle, which is different from typical orogenic gold deposits. Thus, it is proposed that they are named “Jiaodong-type” gold deposits.©2021 China Geology Editorial Office.     

十红滩地浸砂岩铀矿层间氧化带蚀变矿物群

十红滩砂岩型铀矿床是我国大型层间氧化带型砂岩铀矿床之一。层间氧化带型砂岩铀矿含矿砂层在含氧含铀水的渗入径流过程中,由于水介质性状的变化,在与砂体发生水岩作用时形成了完全氧化带、不完全氧化带、还原带和原生带等不同地球化学亚带及其相对应的蚀变矿物群,即完全氧化带为褐铁矿(针铁矿、水针铁矿)、伊利石、蒙脱石、少量黄钾铁矾的蚀变矿物群;不完全氧化带为褐铁矿(针铁矿、水针铁矿)、黄钾铁矾、蒙脱石、伊利石、少量绿泥石、高岭石的蚀变矿物群;还原带为沥青铀矿、黄铁矿、高岭石、绿泥石、少量蒙脱石、伊蒙混层粘土、伊利石和碳酸盐等新生蚀变矿物群;原生带的新生蚀变矿物群以黄铁矿、绿泥石、高岭石为主,有时出现少量碳酸盐、蒙脱石和伊利石等。     

苏鲁超高压变质岩中地震波速随围压的变化规律

我们在10~800MPa的静水压力下测量了中国大陆科学钻探(CCSD)主孔岩心和采自苏鲁地区地表露头上的共68块典型超高压变质岩试样的地震波速,并建立了波速和围压的定量关系,成功地解释了描述这一定量关系方程中4个参数的物理意义。笔者相信,本文将为超高压变质岩地区以及新老俯冲带地震波资料的解释提供必不可少的理论和实验支撑。     

赣中变质岩带地质地球化学演化特征

赣中变质岩带由结晶基底和褶皱基底组成。从结晶基底→褶皱基底,变质泥质岩类SI O2含量降低,AL2O3含量增加;变粒岩、石英片岩、硅质岩SI O2含量显著升高,AL2O3含量显著降低;NA2O含量显著降低,K2O的含量有明显的升高,NA2O/K2O值呈显著的降低趋势;FEO、MGO、TI O2及全铁含量(FE2O3 FEO)呈降低的趋势,但FE2O3升高,FE2O3/FEO值显著增高。铁族元素TI、V、CR升高,MN、CO、NI降低;亲铜元素ZN显著升高;大离子亲石元素LI、RB、SR显著降低,U、TH、BA显著升高,SR/BA值急剧降低;LA、CE、YB、NB、Y元素升高;稀土总量、轻稀土含量、轻重稀土比值、轻重稀土相互分离程度、EU亏损程度增加,说明它们原岩沉积环境的差异性,但它们的重稀土含量、LA/CE值、SM/ND值变化很小,稀土配分曲线相互平行反映它们源区岩石的一致性及继承性。从结晶基底→褶皱基底,岩石的ΕND(0)、(~(206)PB/~(204)PB)I、(~(207)PB/~(204)PB)I、(~(208)PB/~(204)PB)I值由低→高;地壳趋于成熟,结晶基底形成于岛弧环境,褶皱基底形成于活动大陆边缘环境。     

四川丹巴穹状变质地体

四川西部丹巴地区最为引人注目的地质构造是穹状变质地体的发育。华北、扬子和羌塘三个板块之间的南北向和东西向双向收缩,引起区内发育了大小不等的十几个穹状变质地体,自北而南有马奈、春牛场、丹巴、公差、格宗等变质穹隆。多数穹隆的核部出露的是前寒武纪的片麻岩和混合岩,例如春牛场侵入体。其中的片麻岩原岩、黑云母和角闪石质片麻岩均属本区最老的岩石。它不整合于志留纪地层之下,年代学研究证明其年代属新元古代(大约865~785Ma)。混合岩从形态上说,多为条带状,偶见角砾状的角闪石质混合岩。但是也有不少穹隆,核部是花岗岩类。岩石化学研究证明,它们大多属于S型花岗岩,仅个别为I型。穹状变质地体的外围变质带可分三类:(1)巴罗带型区域递增变质带,有的显示变质带的倒转;(2)巴肯型变质带;(3)低级区域变质带,多数是中压绿片岩相。巴罗带变质的泥质岩,多数变晶矿物如黑云母、十字石、石榴石均具早期低级变质矿物的定向包裹物,显示明显叠加变质的信息。变质泥质岩的∑REE=(195~274)×10-6,(La/Yb)n=0·811~1·917。稀土配分曲线和微量元素蛛网图具Nb、P、Ti负异常,显示大陆地壳的特征,是陆缘碎屑物质区域变质产物。巴肯带出露于丹巴以北,主要变质泥质岩是夕线石片麻岩类,常见铁铝榴石而少见堇青石,说明原岩富铁贫镁,局部出现锌铁尖晶石。由北侧的巴肯带到巴罗型变质的公差穹隆到南部的格宗穹隆变质带是从高温到低温连续变化的。因之,我们倾向于认为松潘—甘孜造山带的东南缘是一个规模较大的、呈NE向分布的低—中压区域变质带,总体是一条热轴,垂直走向,向东南温度逐步降低。据前人同位素年龄资料:M1巴罗型区域变质发生于约210~205Ma,马奈花岗岩U-Pb锆石年龄为(197±6)Ma。M2巴肯型变质与岩体侵入有关,年龄约为164Ma。M3喜马拉雅期重结晶的黑云母年龄约为30Ma。总之,丹巴变质穹隆的形成是青藏高原东北部地质构造演化中重要的一幕,其主要活动期起于印支晚期最后结束于喜马拉雅期的隆升和挤出。依据低压高温变质带的空间分布,推测本区印支末期存在一NE向的热轴,同时也是S型花岗岩体的出露区。至于木里一带穹隆与丹巴穹隆在变质程度上的差异,应当归因于印支晚期的陆壳增厚过程中,北倾南倒逆冲剪切造成区域热流的不均一性。也说明了青藏高原东北缘在喜山期隆升之前具有复杂的构造变质历史。