Attribution of the Langshan Tectonic Belt: Evidence from zircon U-Pb ages and Hf isotope compositions

This study describes a previously unidentified Neoproterozoic mafic dyke emplaced in the northern flank of the Langshan Tectonic Belt. This dyke intruded into the micaquartz schist of the Zhaertaishan Group, and yielded an age of 908 ± 8 Ma. The youngest U-Pb ages of micaquartz schist from the Zhaertaishan Group in the Langshan area were 1118 ± 33 Ma,1187 ± 3 Ma and 1189 ± 39 Ma,suggesting that the depositional age of the protolith of the schist was between 908 ± 8 Ma and 1118 ± 33 Ma. In addition, 436 U-Pb age data and 155 Lu-Hf isotopic data from six samples in the Langshan Tectonic Belt and one Permian greywacke from the Wuhai area show distinct differences between the northern and southern flanks of the Main Langshan area. The U-Pb ages of the northern flank are primarily Meso-Neoproterozoic; similar ages have not been identified in the southern flank to date.Moreover, two-stage Hf model ages of the northern flank feature three age peaks at ～900 Ma,～1700 Ma and ～2600 Ma; this differs from Hf model ages of the southern flank, which feature one strong age peak at ～2700 Ma. These results suggest that the northern and southern flanks of the Main Langshan area have different geochronologic characteristics and should be divided further. Based on the U-Pb ages and Hf model ages, the northern and southern flanks of the Main Langshan area are named the North and South Langshan Tectonic Belts. Comparison of the U-Pb age and two-stage Hf model age distributions from the North Langshan Tectonic Belt, South Langshan Tectonic Belt, Alxa Block and the North China Craton(NCC) reveal that the North Langshan Tectonic Belt is similar to the Alxa Block and that the South Langshan Tectonic Belt is similar to the NCC. In addition, the zircon U-Pb age of 860 ±7 Ma commonly observed in the Alxa Block was detected in the Permian greywacke from the Wuhai area of the NCC, which suggests that the amalgamation of the North and South Langshan Tectonic belts(i.e.,the amalgamation of the Alxa Block and the NCC), occurred between Devonian and late Permian.     

全国油气资源战略选区调查工程进展与成果

2016—2018年期间,由中国地质调查局油气资源调查中心牵头组织实施的“全国油气资源战略选区调查工程”,以实现“新区、新层系、新类型、新认识”四新领域油气调查战略发现和突破,推动创建油气勘查开发新格局为目标,按照总体部署、分步实施原则,组织开展了长江经济带页岩气调查、北方新区新层系和松辽盆地页岩油调查油气调查三大科技攻坚战。在基础地质调查基础上,评价优选了一批页岩油气有利目标区,部署实施了二维地震、参数井和压裂试气工程,实现了长江中游下古生界页岩气、松辽盆地白垩系青山口组页岩油、塔里木盆地温宿凸起新近系油气、准噶尔盆地南缘二叠系芦草沟组油气和侏罗系西山窑组煤层气以及银额盆地居延海坳陷石炭系—二叠系油气调查等一系列重大突破和发现,初步摸清了新区新层系资源潜力。这些成果大大提振了南方复杂构造区页岩气、陆相页岩油和北方新区新层系油气资源勘查的信心,推动了油气地质调查与科技创新的深度融合,形成了油气成藏理论机理新认识,发挥了公益性油气资源调查的引领和带动作用。     

Geochemical characteristics and genetic type of a lithium ore (mineralized) body in the central Yunnan Province,China

Lithium ore (mineralized) bodies in the area A of central Yunnan Province belong to a sedimentary-type, which are controlled by stratum. The studied ore (mineralized) body mainly occurs in the Middle Permian Liangshan Formation. This work described the morphology, structures, main ore types and geochemical characteristics of this ore body in detail, and discussed the ore-forming material source, occurrence state of lithium and the formation mechanism of lithium ores to clarify the prospecting marks. In the further exploration, comprehensive evaluation of the lithium resources of known bauxite ore bodies in central Yunnan Province should be strengthened, and the exploration of hidden lithium ore bodies should be intensified in order to discover more large and super-large lithium orebodies, which will fill the gap of the national demand for lithium resources, and promote the national defense construction and new energy industry development.     

秦祁昆成矿域古生代区域成矿规律

位于古亚洲成矿域和古特提斯成矿域之间的秦祁昆成矿域,是我国大陆的一个重要成矿区域,其丰富的固体矿产资源、多种成矿作用的复杂表现以及独特的区域成矿背景已为人们所关注。通过对这一成矿域古生代主要矿床的资源类型、区域分布、成矿作用演化及成矿背景的研究,重点讨论了古生代区域成矿的时空演化,并归纳总结出古生代区域成矿的成矿元素及组合、成矿作用演化、区域成矿的旋回性、成矿区域迁移和成矿发生的主要时间段5个方面的总体规律。     

Illite crystallinity study of the Cretaceous Shimanto Belt in the Akaishi Mountains, eastern Southwest Japan

Abstract Illite crystallinity (IC) analyses in the Upper Cretaceous Shimanto accretionary complex of the southern Akaishi Mountains, eastern Southwest Japan confirm the applicability of this technique for evaluating the grade of diagenesis/metamorphism in a sediment-dominated accretionary complex. Reproducibility analyses of IC values show a variance of about 15% from the mean. Data from three traverses, which transect across-strike sections of ∼25 km, clearly demonstrate that the IC distributions have specific overall trends. The IC values belong to the lQwer anchizone and the zone of diagenesis. The IC distributions may be controlled locally by structural features, but there are no distinct relationships with regional-scale geological structures. This may indicate that the heterogeneous geothermal rise affected the pre-existing structural and diagenetic/metamorphic framework of the accretionary sequence. Along-strike variations of grade tend to increase toward the northeast where a Middle Miocene granitoid occurs. Hence, the original diagenetic/metamorphic framework of this part of the Shimanto Belt was presumably overprinted during the Middle Miocene.     

陕西宁强巩家河—蒲家沟地区火山岩地质特征及金、银多金属成矿预测

宁强巩家河—蒲水沟地区出露的元古界碧口群为浅变质火山—沉积岩系，火山岩为钙碱性系列的细碧—角斑岩建造，产于岛弧构造环境，火山活动以裂隙式喷溢为主，岩浆演化总体反映为一个大的正向旋回。金、银多金属矿化主要产在火山溢出间歇阶段的短暂喷发所形成的火山碎屑岩夹层中或不同岩性的过渡转换部位。矿化受后期改造富集特点明显。     

构造改造成矿机制：——四川羊石坑汞矿成矿作用探讨

羊石坑汞矿床是位于四川省秀山县境内的大型汞矿床，产于下寒武统清虚洞组碳酸盐岩中，受地层和构造双重控制，并以细脉浸染型为特征而区别于我国其他大型汞矿床。概括了该矿产出的区域地质背景、物质来源和构造控矿特征，通过对不同构造部位矿物、元素及同位素等的分布、分配特征和矿床地质地球化学研究，揭示了成矿物质来自沉积地层，矿源层的形成与同生断裂活动和深部物质加入有关，构造－热液活动对矿源层的改造导致了矿床形成，     

Radiolarian-bearing conglomerate from the Hayang Group, the Kyongsang Supergroup, southeastern Korea

The non-marine Cretaceous Kyongsang Supergroup, which is divided into the Sindong, the Hayang and the Yuchon groups, is widely distributed in southeastern Korea. Radiolarian-bearing pebbles are collected from the conglomerates of the Kumidong and the Kisadong formations of the Hayang Group. The age of radiolarian fossils range from Late Permian to Middle Jurassic. In Korea, Permian to Middle Jurassic marine chert beds are not exposed. The directions of paleocurrents of the Kumidong and the Kisadong formations are mainly from the northeast to southwest. During Cretaceous time, the Mino-Tamba Belt, within which Permian to Middle Jurassic chert beds are exposed, is suggested to have been located northeast of the Kyongsang Basin. The radiolarian faunas of the Hayang Group are similar to those of the Mino-Tamba Belt and other associated Mesozoic accretionary belts in Japan (e.g. the Ashio Belt). The provenance of the radiolarian-bearing pebbles collected from the Kumidong and the Kisadong formations is interpreted to be the Mino-Tamba Belt and other associated Mesozoic accretionary belts in Japan.     

The Araçuaí-West-Congo Orogen in Brazil: an overview of a confined orogen formed during Gondwanaland assembly

The Neoproterozoic Adamastor-Brazilide Ocean was generated during the breakup of the Rodinia supercontinent, and remnants of its oceanic lithosphere have been found in the Brasiliano-Pan African orogenic system that includes the Araçuaí, West-Congo, Brasília, Ribeira, Kaoko, Dom Feliciano, Damara and Gariep belts. The Araçuaí and the West-Congo belts are counterparts of the same Neoproterozoic orogen. The first belt comprises two thirds of the Araçuaí-West-Congo Orogen. This orogen is rather unique owing to its confined nature within the embayment outlined by the São Francisco and Congo cratons. In spite of this, the presence of ophiolitic remnants, and a calc-alkaline magmatic arc, indicate that the basin/orogen evolution comprise both oceanic spreading and consumption. It is assumed that coeval Paramirim and Sangha aulacogens played a key role by making room for the Araçuaí-West-Congo Basin. Sedimentary successions record all major stages of a basin that evolved from continental rift, when glaciation-related sedimentation was very significant, to passive margin. Rifting started around 1.0–0.9 Ga. The oceanic stage is constrained by an ophiolitic remnant dated at 0.8 Ga. If the cratonic bridge that once linked the São Francisco and Congo palaeocontinental regions did not hinder the opening of an ocean basin, it certainly limited its width. As a consequence, only a narrow oceanic lithosphere was generated, and it was subducted afterwards. This is also suggested by orogenic calc-alkaline granitoids occuping a small area of the orogen. Geochronological data for pre-, syn- and late-collisional granitoids indicate that the orogenic stage lasted from 625 Ma to 570 Ma. A period of magmatic quiescence was followed by intrusion of postcollisional plutons at 535–500 Ma. The features of the Araçuaí-West-Congo Orogen suggest the development of a complete Wilson Cycle in a branch of the Adamastor Ocean, which can be interpreted as a gulf with limited generation of oceanic lithosphere.     

论成矿台阶

成矿台阶系指同一成矿区，同一成矿系列的同一类型矿床的主要矿体赋存在相应的标高范围内，湘南－粤北地区，铌钽矿床的成矿台阶为640－980m;石英脉－黑钨矿床600－1400m，石英脉一白钨矿床100－400m，矽卡岩型白钨矿床100－860m;浅源重熔岩浆系列铅锌矿床600－1100m，深源同熔岩浆系列铅锌矿床－200－100m，最深可达－700m;石英脉型锡石矿床650－1400m，锡石－硫化物，蚀变花岗岩型，云英岩型锡矿床450－650m，香花岭，界牌岭锡多金属矿床－200－270m，利用成矿台阶新理念，指导上述矿床的勘查，可以收到事半功倍的探矿效果。