Geophysical prospecting of copper-nickel deposits in Beishan rift zone,Xinjiang

The Beishan rift zone in Xinjiang Uygur Autonomous Region was formed due to strong activities of faults on the basement of the Tarim continental crust. Despite the fact that many geological research results of the rift zone have been achieved, only a few studies have been conducted on its regional geophysical characteristics. In this paper, the gravity and magnetic anomalies of the rift zone were highlighted through specific data processing of 1:50000 high-precision aeromagnetic data and gravity data with a grid spacing of 2 km × 2 km. Based on this, the geophysical evidence for the scope and internal structures of the Beishan rift zone was obtained for the first time. The distinct characteristics of magnetic and gravity fields in the areas to the north and south of the Beishan rift zone reveal that deep faults exist between the Beishan rift zone and the geological units on the southern and northern sides. Furthermore, the faults on the two areas contain the bidirectional thrusts and have flower-shaped structures according to the characteristics of the magnetic and gravity fields. The Beishan rift zone can be divided into two tectonomagmatic zones, namely the Zhongposhan-Bijiashan-Cihai-Baishanliang zone (the northern zone) and the Bayiquan-Qixin-Baishan zone (the southern zone). The northern zone can be further subdivided into three comet-shaped anomaly groups (tectonomagmatic areas), while the southern zone can be further subdivided into two tectonomagmatic areas. According to the characteristics of aeromagnetic anomalies and gravity field, 19 mafic-ultramafic complexes were delineated. The known Pobei, Hongshishan, and Qixin complexes are all located within the inferred complexes, with estimates of total explored resources of Ni, Cu, and Au of 3×10⁶ t, 10×10³ t and 10 t, respectively. The prospecting of high-grade copper-nickel deposits should focus on the periphery and deep parts of the known and inferred mafic-ultramafic complexes. Among them, the peripheral strata of the complexes specifically have great prospecting potential of large-scale high-grade copper-nickel deposits of magma injection type. Finally, this paper analyzed the application effects of the rapid airborne-ground-drilling synergetic exploration method in the prospecting of copper-nickel deposits in Qixin, Beishan, Xinjiang, which will provide references for further exploration of copper-nickel deposits in Beishan area, Xinjiang.©2021 China Geology Editorial Office.     

鲜水河活动断裂带航磁异常特征

鲜水河断裂带的构造几何特征及其地质背景是进一步研究鲜水河断裂带的孕震性的重要基础资料。从收集、处理、解释航磁资料着手，在前人的工作基础上，进一步分析研究了鲜水河断裂带的几何形态特征及鲜水河地区的地质背景，特别是深部构造情况，揭示了断裂带的几何形态结构特征与深部构造之间的联系，并发现了一个可能与孕震有关的环形构造（岩体）。     

羌塘盆地的基底组成、结构特征及其意义

通过对羌塘盆地地质、地球物理资料的综合分析认为 ,羌塘盆地的变质岩系从上至下可分为果干加年日组、玛依岗日组、戈木日组和阿木岗组 ,其中后二者构成了盆地的结晶基底。大地电磁与航磁异常结果均揭示出 :盆地基底具有较强的东西分块性 ;结晶基底在高原后期隆升时遭到强烈的改造 ,其间加入了电性上表现为高阻与低阻的物质成分 ,使得结晶基底的连续性、均质性改变     

唐山震区结晶基底磁性界面的初步探讨

扼要地叙述了频率域磁性单界面反演方法的基本原理,运用该程序对唐山震区航磁资料进行了数字处理,获得了震区结晶基底磁性界面的定量特征。结果表明唐山处在华北平原北部与燕山隆起毗邻的褶皱拗陷中,震源区开平向斜的底部基底磁质界面为一拗陷,周围受3条深断裂切割围限。文章最后,结合人工地壳测深、地形变、地应力等成果进行了分析研究,探索了唐山地震的发生及孕育过程     

Constraints on the evolution of the Taranaki volcanoes,New Zealand,based on aeromagnetic data

Aeromagnetic anomalies measured over the three relict andesite volcanoes (Paritutu, Kaitake and Pouakai) in Taranaki are largely dominated by topographic effects. Three-dimensional magnetic modelling, well constrained by both contrasting levels of exposure and previous gravity models, shows that the bulk magnetization of the andesite edifice and edifice core of both Kaitake and Pouakai is 2.5–3.5 A m^-1 in a direction close to that of the present earth's field. However, the large andesite dyke/stock complexes below all three edifices and a localized area of the Kaitake edifice directly above the centre of the subedifice complex have anomalously low bulk magnetizations of 0.3–1.0 A m^-1 in the same direction. These subsurface complexes represent dyke injection from magma chambers situated in the basement, probably below 6 km depth. Here, we deduce that heat from these magma chambers drove hydrothermal convection systems causing widespread demagnetization, especially in the subedifice complexes, but also locally within the edifices themselves. A lesser degree of demagnetization at Pouakai, the youngest of the three volcanoes, may indicate a shorter and consequently more intense period of activity at this centre.     

茶陵-永兴盆地南缘航磁(△T)异常特征及其与铀成矿的关系

本文对茶陵-永兴盆地南缘的航磁(△T)异常进行了研究。铀矿区内航磁异常的解释结果与已知铀矿体的对比表明航磁异常与铀矿化有关。据此推测,与已知矿区类似的其它航磁异常也都可能反映了不同规模的隐伏铀矿化。磁性矿物的相对富集区可能代表着铀沉积的理想还原环境。     

http://www.sciencedirect.com/science/article/pii/S1674987114000292

Aeromagnetic anomaly zonation of the Ordos Basin and adjacent areas was obtained by processing highprecision and large-scale aeromagnetic anomalies with an approach of reduction to the pole upward continuation.Comparative study on aeromagnetic and seismic tomography suggests that aeromagnetic anomalies in this area are influenced by both the magnetic property of the rock and the burial depth of the Precambrian crystalline basement.Basement depth might be the fundamental control factor for aeromagnetic anomalies because the positive and negative anomalies on the reduction to the poleupward-continuation anomaly maps roughly coincide with the uplifts and depressions of the crystalline basement in the basin.The results,together with the latest understanding of basement faults,SHRIMP U-Pb zircon dating of metamorphic rock and granite,drilling data,detrital zircon ages,and gravity data interpretation,suggest that the Ordos block is not an entirety of Archean.     

特殊区域旋翼无人机航磁测量研究

为解决地面人员难以到达的特殊区域大比例尺磁测数据获取问题,本文提出一种基于三轴磁通门传感器,采用旋翼无人机进行航空磁测的方法.项目组研制适合旋翼无人机搭载的航磁数据记录仪,并完成旋翼无人机、三轴磁通门传感器、航磁数据记录仪的集成工作,开展了三轴磁通门传感器安装点位噪声水平试验、地面空中对比试验、磁性体识别试验、动态飞行一致性试验、区域飞行试验.旋翼无人机航磁系统具有操作简单、设备轻便、效率高的特点,能在地面人员难以达到的区域开展低空航磁测量.中国四川省黑竹沟地区是地磁异常区域,项目组在该区域内的沟壑、峡谷、湖泊等实地开展了野外应用测试,完成了这些特殊区域的航磁调查工作.     

中国北部古元古代地壳尺度的伸展拆离和硅铝壳内活动带:北东向线性航磁异常的地质构造解释

早前寒武纪地质构造和分辨率大于120km的长波航磁异常特征表明:塔南—华北—朝鲜北部(狼林地块)具有类似的太古宙结晶基底,它们可能曾经是太古宙统一克拉通的组成部分。20~120km分辨率的中波航磁异常凸现一组北东东—北北东走向、改造太古宙高级变质结晶基底的线性航磁异常,它们分别对应于地壳尺度的长寿断裂。古元古代阶段沿着它们发生了大规模的左行韧性伸展剪切运动,在使塔南、朝鲜北部陆块分别向南西和北东伸展拆离的同时,华北克拉通内部也出现了有限的裂解,并伴随着硅铝壳内活动带的发育。本文将这些古元古代阶段韧性伸展剪切带划分为塔南与华北陆块之间的西部剪切带系统、华北与狼林陆块之间的东部剪切带系统和华北陆块内部的青龙—太行山—中条山等3个独立的剪切带系统。西部韧性剪切系统由阿尔金、大同—环县、以及它们之间的狼山—吉兰泰、雅布赖山等次级剪切带组成,控制古元古代阿拉善群和上集宁群的孔兹岩系为代表的硅铝壳内活动带的沉积—构造演化。东部韧性剪切系统包括沂水和新宾—桦甸等韧性剪切带,相关的古元古代活动带以胶东地区的粉子山群、荆山群和辽吉地区的辽河群为代表。中部韧性剪切带系统以太行山地区阜平群、赞皇群中出现的角闪岩相糜棱片麻岩、眼球状糜棱岩带为代表,发育b-型线理,指示近水平或低角度斜滑性质的左行韧性剪切,相关的古元古代活动带包括双山子—青龙河、五台—滹沱、甘陶河—东焦、吕梁、中条以及济宁等。不同规模的古元古代活动带彼此并不相连,以发育变质沉积—火山岩建造为主体,岩石磁化率明显低于太古宙高级变质结晶基底,与之相关的韧性剪切带则以其透入性矿物线理产生了增强的磁化率各向异性,两者共同构建了地壳尺度北东东—北北东向线性航磁异常带。古元古代末的中条运动使上述硅铝壳内活动带褶皱回返,塔南—华北—朝鲜北部陆块重新焊接,形成近纬向展布逐渐稳定的中轴大陆克拉通,上述地壳尺度的韧性伸展剪切带在中元古代以后的地质历史中,大多被后期不同性质的脆性断裂所追踪。     

中国东北地区航磁特征及居里面分析

中国东北地区位于西伯利亚和华北地块之间,中、新生代本区受西太平洋板块俯冲的影响,由于多期构造作用,导致地质构造形态极为复杂.本文通过分析航磁异常场,认识研究区的构造特征,并利用航磁异常数据的功率谱法反演居里等温面.航磁异常场和居里面分布特征均揭示研究区地质构造发展具有继承性;通过居里面起伏变化特征,并结合满-绥地学断面、及与大地热流分布的关系,讨论研究区地壳的热结构状态特点,结果显示居里面起伏趋势与软流圈起伏具明显的相关性;结合地震活动和地震层析成像研究,探讨了太平洋板块俯冲受阻引起岩浆和火山活动,进而导致居里面上隆的影响机制.