Andean Geology最新文献_第6页

Geochronology of the Real Cordillera, the inner magmatic arc of Bolivia 玻利维亚内部岩浆弧Real Cordilera的地质年代

IF 0.9 4区地球科学 Q1 Earth and Planetary Sciences

Andean Geology

Pub Date : 2021-06-15 DOI: 10.5027/ANDGEOV48N3-3326

A. R. Iriarte, U. Cordani, Kei Sato

The Real Cordillera granitoids are a suite of Triassic and Oligocene plutons located at the core of the Eastern Cordillera of the Central Andes of Bolivia. Its geotectonical setting, chemical and ore composition make them part of the so called “Inner Magmatic Arc” which differs from the actual “Magmatic Arc” located immediately to the west. U-Pb SHRIMP ages were obtained in order to constrain their crystallization ages. The Triassic group yielded the following results: 240 ± 2 Ma for the Huato granite, 230.7 ± 1.3 Ma for the Illampu granodiorite, 222.2 ± 2.4 Ma for the Huayna Potosí granite and 221.9 ± 1.5 Ma for the Taquesi granodiorite. For the Oligocene group we obtained two ages of 26.87 ± 0.26 and 26.88 ± 0.21 Ma both for the Quimsa Cruz granite. Mafic enclaves from the Illampu and Taquesi granodiorites report ages that were older than their respective granitoid hosts, yielding 234.1 ± 1.3 Ma and 227 ± 1.3 Ma, respectively. Secondary processes related to regional thermal anomalies and magmatic melt-enrichment, reset the K/Ar and U/Pb isotopic systems, producing: a) younger ages by Ar loss and b) older ages by U/Pb isotopic ratios reorganization. As noted in previous studies, the Zongo/Kuticucho Triassic granite yielded extremely high U enrichment in most zircon analysed, producing reset of U/Pb ratios, wide span in age ranges and reverse discordia curves that obscure its actual crystallization age. Relatively abundant zircon inheritance was found in these “cold” and inheritance-rich granitoids, with ages suggesting provenance from early Paleozoic metapelites that also recycled older sources. This relatively abundant xenocrystic inheritance records the influence of the Gondwanide orogeny (336-205 Ma) as an overall subduction arc environment, punctuated at its final stage with the imprint of a continental rifting (245-220 Ma).

真正的科迪勒拉花岗岩类是位于玻利维亚中部安第斯山脉东部科迪勒拉岩心的一套三叠纪和渐新世岩体。它的大地构造环境、化学和矿石组成使其成为所谓的“内岩浆弧”的一部分，与紧邻西部的实际“岩浆弧”不同。为了约束其结晶年龄，测定了U-Pb SHRIMP年龄。三叠纪花岗闪长岩为240±2 Ma，伊兰普花岗闪长岩为230.7±1.3 Ma，华那Potosí花岗闪长岩为222.2±2.4 Ma，塔克西花岗闪长岩为221.9±1.5 Ma。渐新世花岗岩年龄分别为26.87±0.26 Ma和26.88±0.21 Ma。Illampu和Taquesi花岗闪长岩的镁铁质包裹体的年龄分别为234.1±1.3 Ma和227±1.3 Ma，比它们各自的花岗类寄主更早。与区域热异常和岩浆熔体富集有关的二次过程重置了K/Ar和U/Pb同位素系统，产生了:a) Ar损失导致的年轻年龄和b) U/Pb同位素比例重组导致的更老年龄。正如之前的研究所指出的，Zongo/Kuticucho三叠纪花岗岩在大多数分析的锆石中具有极高的铀富集，产生了U/Pb比值的重置，年龄范围的跨度很大，反向的不均匀曲线模糊了其实际的结晶年龄。在这些“冷”且继承丰富的花岗岩中发现了相对丰富的锆石继承，年龄表明物源来自早古生代的变长岩，也有旧源的再循环。这种相对丰富的异晶继承记录了冈瓦尼德造山运动(336-205 Ma)作为一个整体的俯冲弧环境的影响，在其最后阶段被大陆裂陷(245-220 Ma)的印记所打断。

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引用次数: 1

A Holocene tephra layer within coastal aeolian deposits north of Caleta Olivia (Santa Cruz Province, Argentina) Caleta Olivia（阿根廷圣克鲁斯省）北部海岸风成沉积物中的全新世火山灰层

IF 0.9 4区地球科学 Q1 Earth and Planetary Sciences

Andean Geology

Pub Date : 2021-05-31 DOI: 10.5027/ANDGEOV48N2-3290

G. Zanchetta, M. Pappalardo, A. Roberto, M. Bini, I. Arienzo, I. Isola, A. Ribolini, G. Boretto, Enrique Fuck, D. Mele, M. D’Orazio, F. Marzaioli, I. Passariello

In this paper we illustrate the stratigraphy, geochronology, and geochemistry (major, minor, trace elements and Sr-isotopes) of a Holocene tephra layer found within coastal sedimentary deposits north of Caleta Olivia (Santa Cruz Province, Argentina). The stratigraphic succession comprises beach deposits with basal erosive surface resting on the local substrate (“Formacion Patagonia”) followed by a poorly developed paleosoil. The paleosoil is covered by a lenticular fine-grained (Mdφ: 5.2, 0.027 mm), well sorted (σφ: 1.2) volcanic ash layer and aeolian sands. The geochemical composition of shard fragments points to an origin from the Hudson volcano, located in the southern Andes, ca. 400 km to the west. The geochemistry, Sr-isotopes and the radiometric constraints (younger than the age of the underlying marine layer dated at ca. 4,100 a cal BP) further allow correlating this tephra with the so-called H2 eruption (ca. 3,900 a cal BP). This finding is of interest owing to the poor preservation potential of tephra within the Late Holocene sedimentary deposits of the Atlantic coast of Patagonia and represents the first finding of H2 eruption in this area, improving our knowledge of the dispersion of the fine-grained distal deposit of the Hudson volcanic explosive activity, thus allowing a better estimate of the eruptive dynamics and the risks associated with the Hudson volcano.

在本文中，我们展示了在Caleta Olivia（阿根廷圣克鲁斯省）以北的海岸沉积矿床中发现的全新世火山灰岩层的地层学、地质年代和地球化学（主要、次要、微量元素和Sr同位素）。地层序列包括海滩沉积物，其基底侵蚀面位于当地基底上（“Formacion Patagonia”），然后是发育不良的古土壤。古土壤被透镜状细粒（Mdφ:5.20.027mm）、分选良好（σφ:1.2）的火山灰层和风积沙覆盖。碎片的地球化学成分表明其来源于哈德逊火山，该火山位于安第斯山脉南部，向西约400公里处。地球化学、Sr同位素和辐射限制（比下伏海洋层的年龄小，约4100 a cal BP）进一步使该火山喷发与所谓的H2喷发（约3900 a cal BP）相关。这一发现之所以令人感兴趣，是因为巴塔哥尼亚大西洋海岸晚全新世沉积矿床中的火山灰岩保存潜力较差，这是该地区首次发现H2喷发，提高了我们对哈德逊火山爆发活动细粒远端矿床分散性的了解，从而能够更好地估计哈德逊火山的喷发动力学和相关风险。

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引用次数: 1

Magnetic fabric of the Parashi stock and related dyke swarm, Alta Guajira (Colombia): The Caribbean-South American plates oblique convergence 上瓜希拉省(哥伦比亚)Parashi岩群和相关岩脉群的磁性结构:加勒比-南美板块斜辐合

IF 0.9 4区地球科学 Q1 Earth and Planetary Sciences

Andean Geology

Pub Date : 2021-05-31 DOI: 10.5027/ANDGEOV48N2-3332

C. Bustamante, C. Archanjo, A. Cardona, Marcela Restrepo

Anisotropy of magnetic susceptibility (AMS) and anhysteretic remanence (AAR) were used to evaluate the emplacement history of the Parashi stock and related dyke swarm situated in NW Colombia. The average magnetic susceptibility of 4.5×10-2 SI, in conjunction with low-coercivity components provided by the isothermal remanence and thermomagnetic curves with net Verwey and Curie transitions, indicates that multidomain magnetite records the anisotropy directions. The similar orientation and shape of the AMS and AAR ellipsoids indicate the absence of very fine magnetite with an inverse fabric. The magnetic foliation is the best-defined fabric element in these rocks and outlines a concentric structure, elongated parallel to the NE-SW direction of the pluton. Crystallisation age of the stock and dykes (51-47 Ma), along with pressure of emplacement determination indicate that the stock and the dyke swarm probably formed simultaneously, and they were emplaced in the shallow crust (

利用磁化率各向异性（AMS）和无磁滞剩磁（AAR）来评估位于哥伦比亚西北部的Parashi岩群和相关岩脉群的侵位历史。4.5×10-2 SI的平均磁化率，以及等温剩磁和具有净Verwey和居里跃迁的热磁曲线提供的低矫顽力分量，表明多畴磁铁矿记录了各向异性方向。AMS和AAR椭球的相似方向和形状表明不存在具有相反组构的非常细的磁铁矿。磁性叶理是这些岩石中定义最好的组构元素，勾勒出一个同心结构，平行于深成岩体的东北-西南方向延伸。岩堆和岩脉的结晶年龄（51-47Ma），以及侵位压力的确定表明，岩堆和岩墙群可能同时形成，它们侵位在浅地壳中(

引用次数: 3

The first Peruvian record of Enchodus (Actinopterygii, Aulopiformes, Enchodontidae) in the Upper Cretaceous Vivian Formation 上白垩纪Vivian组Enchodus（Actinopterygii，Aulopiformes，Enchodonidae）的秘鲁首次记录

IF 0.9 4区地球科学 Q1 Earth and Planetary Sciences

Andean Geology

Pub Date : 2021-05-31 DOI: 10.5027/ANDGEOV48N2-3337

Soledad Gouiric-Cavalli, A. L. Cione, D. Tineo, L. Pérez, Martín Iribarne, Miguel A. Allcca Torres, D. Poiré

We describe isolated teleostean teeth found in no association with the jaw bone. The specimens have been recovered in Late Cretaceous marine deposits of the Vivian Formation in the Peruvian Sub-Andean Region. The deposition sequence from where the teeth come is interpreted as a shallowing-upward sequence of low salinity. The fish material is identified as Enchodus aff. E. gladiolus based on the presence of a small but well-developed post-apical barb, an anterior cutting edge, the crown is symmetrical in cross-section, have a sigmoidal profile, and bears strong ridges (=striations). The Peruvian material differs from the typical E. gladiolus teeth in having a faintly serrated anterior cutting edge which is absent in most specimens referred to E. gladiolus. We also highlight that taxonomic assignments made based on isolated teeth must be taken with care. Despite scarce, the material recovered denotes that the marine units of Peru can give valuable information about the Pacific fish fauna during the Late Cretaceous.

我们描述了与颌骨无关的孤立硬骨鱼牙齿。这些标本是在秘鲁亚安第斯地区晚白垩纪Vivian组的海洋沉积物中发现的。牙齿所在的沉积序列被解释为低盐度的向上变浅序列。该鱼类材料被鉴定为Enchodus aff。E.唐菖蒲基于一个小但发育良好的顶端后倒钩，一个前切削刃，冠部横截面对称，具有乙状轮廓，并具有强大的脊（=条纹）。秘鲁材料与典型的唐菖蒲牙齿的不同之处在于，它有一个锯齿状的前切削刃，这在大多数唐菖蒲标本中都没有。我们还强调，必须谨慎对待基于孤立牙齿的分类分配。尽管材料稀少，但所回收的材料表明，秘鲁的海洋单元可以提供有关白垩纪晚期太平洋鱼类区系的宝贵信息。

引用次数: 3

Remotely-sensed time series of rapid terrace formation in the Laguna del Viedma valley (Patagonia) 巴塔哥尼亚拉古纳德尔维德马河谷快速阶地形成的遥感时间序列

IF 0.9 4区地球科学 Q1 Earth and Planetary Sciences

Andean Geology

Pub Date : 2021-03-03 DOI: 10.5194/EGUSPHERE-EGU21-14866

V. Thorndycraft

The Patagonian Andes were subject to a range of geophysical drivers of landscape incision during the Last Glacial Interglacial Transition and Early Holocene, including tectonic and isostatic uplift, and base level fall triggered by rapid lake drainage events. Deciphering the drivers of river system response during this period is complex, and magnitudes and timescales of landscape change are poorly constrained. Herein, a remotely sensed time series of modern lake elevation change and terrace development is investigated for the Laguna del Viedma valley (Argentina) as a modern analogue of Late Quaternary landscape evolution. The aim of the research was to constrain the timing of terrace formation following lake-level fall of the Laguna del Viedma over a ~35 year period from 1985-2019. The objectives were to: 1) use satellite imagery from the period 1985-2019 to document landform, glacier and lake changes in the study area; 2) use remotely sensed imagery to map the landforms of the Laguna del Viedma valley; and 3) analyse terrace elevations using GIS. In total 7 terrace surfaces were distinguished by remotely sensed geomorphological mapping. The highest, and vegetated, T1 terrace surface (+75 m) was likely formed at the end of the last Holocene neoglacial advance. Viedma glacier recession at this time caused the abandonment of an ice-lateral spillway and allowed a subglacial drainage pathway leading to less stable lake level elevations and terrace formation. Whether the abandonment of T1 was associated with the 4 ka or 0.15 ka neoglacial termination constrains ~45 m of incision, at a rate of 0.01-0.33 m/yr, down to the T3 floodplain level by 1985. There then followed ~20 m of incision to the T4 level, which must have occurred by 2006, constraining a minimum rate of incision of 0.95 m/yr. The time series demonstrates rapid terrace formation occurred by vertical incision and lateral erosion, with mass movements contributing to lateral terrace recession. The implications of the data-set are discussed within the context of the Late Quaternary palaeohydrology of Patagonia where lake level falls of 10s to 100s of metres occurred within most large river systems from 42-52 ⁰S demonstrating that base level falls from lake drainage, and catastrophic floods events, were likely a major driver of landscape change in the region.

巴塔哥尼亚安第斯山脉在末次冰川-冰间过渡和全新世早期受到一系列地貌切割的地球物理驱动因素的影响，包括构造和均衡抬升，以及由快速湖泊排水事件引发的基准面下降。解读这一时期河流系统响应的驱动因素是复杂的，景观变化的幅度和时间尺度受到的约束很差。在此，研究了拉古纳-德尔维德马河谷（阿根廷）现代湖泊高程变化和阶地发育的遥感时间序列，作为晚第四纪景观演变的现代模拟。该研究的目的是在1985-2019年的约35年时间里，限制维耶德马湖湖面下降后阶地形成的时间。目标是：1）利用1985-2019年期间的卫星图像记录研究区域的地貌、冰川和湖泊变化；2）利用遥感图像绘制维耶德马湖流域的地貌图；3）利用GIS对阶地高程进行分析。共有7个阶地表面通过遥感地貌测绘进行了区分。最高的植被覆盖的T1阶地表面（+75m）可能形成于最后一次全新世新冰川推进的末期。此时的维德马冰川退缩导致了冰侧溢洪道的废弃，并允许冰下排水通道，导致湖面高程和阶地形成不太稳定。T1的废弃是否与4 ka或0.15 ka的新冰川终止有关，以0.01-0.33 m/yr的速度限制了~45 m的切口，到1985年降至T3洪泛平原水平。随后，大约20米的切口达到T4水平，这在2006年必须发生，限制了0.95米/年的最小切口率。时间序列表明，垂直切割和侧向侵蚀导致阶地快速形成，岩体运动导致阶地侧向后退。数据集的含义是在巴塔哥尼亚晚第四纪古水文的背景下讨论的，从42-52⁰；S表明，湖泊排水造成的基准面下降和灾难性洪水事件可能是该地区景观变化的主要驱动因素。

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引用次数: 0

Quaternary glaciolacustrine deposits around a Triple Junction site: Paleolakes at the foot of the Northern Patagonian Ice field (Argentina and Chile) 三重交汇点周围的第四纪冰川沉积物：巴塔哥尼亚北部冰原脚下的古湖泊（阿根廷和智利）

IF 0.9 4区地球科学 Q1 Earth and Planetary Sciences

Andean Geology

Pub Date : 2021-01-29 DOI: 10.5027/ANDGEOV48N1-3173

F. Isla, M. Espinosa

The area involved by the triple junction between the South American, Nazca and Antarctic plates activity was affected by Quaternary glaciations. Before 12,800 yrs BP an extended ice field occupied the top of the Patagonian Andes, irradiating glaciers towards the east and the west dominantly. Towards the east, the ice melted in piedmont lakes; towards the west, fjords melted into the Pacific Ocean. The Upper-Pleistocene climate amelioration caused the recession of those glaciers. Some piedmont lakes reversed their Atlantic outflow towards to the Pacific Ocean. The glaciers retreat caused the fluvial reactivations along crustal former faults that were located below the ice. The Patagonian ice field became therefore split into present Northern and Southern fields. At the second largest lake of South America, the Buenos Aires-General Carrera Lake, the water level dropped from about 500 m over present mean sea level to 230 m. Several glaciolacustrine deposits from this area are indicating significant variations caused by climatic changes, volcanism and tectonics, differing in spatial and temporal magnitudes. The triple junction activity involved subduction of the Chile Ridge below the continental South American plate, volcanic activity and faulting. During the glacier melting the Baker River captured three eastern-moving glacial systems towards the southwest, towards the Pacific Ocean. This rapid event is thought to occur 12,800 yrs BP. The lowering of these glaciolacustrine systems should be also interpreted in terms of the tectonic activity in the region and considering other processes operating in the lakes and within the watersheds.

南美洲、纳斯卡和南极板块活动三重交汇处所涉及的区域受到第四纪冰川作用的影响。在12800年前，一个延伸的冰原占据了巴塔哥尼亚安第斯山脉的顶部，主要向东部和西部照射冰川。向东，山前湖泊的冰融化了；向西，峡湾融化成太平洋。上更新世气候的改善导致了这些冰川的衰退。一些山前湖泊将大西洋的外流转向太平洋。冰川的退缩导致了位于冰下的地壳前断层的河流复活。因此，巴塔哥尼亚冰原分为现在的北部和南部冰原。在南美洲第二大湖布宜诺斯艾利斯将军卡雷拉湖，水位从目前平均海平面以上约500米下降到230米。该地区的几处冰川沉积物表明，气候变化、火山活动和构造造成了显著变化，在空间和时间上各不相同。三重交界活动涉及南美洲大陆板块下方智利山脊的俯冲、火山活动和断层活动。在冰川融化期间，贝克河捕获了三个向西南和太平洋移动的东部冰川系统。这一快速事件被认为发生在12800年BP。还应根据该地区的构造活动以及湖泊和流域内的其他过程来解释这些冰川系统的下降。

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引用次数: 1

Gold Deposits in Chile 智利金矿

IF 0.9 4区地球科学 Q1 Earth and Planetary Sciences

Andean Geology

Pub Date : 2021-01-29 DOI: 10.5027/ANDGEOV48N1-3294

J. Cabello

A review of gold and gold bearing base metals deposits in Chile, indicate the existence of at least six different type of ore deposits, most largely formed during the Cenozoic with predominance in the Miocene. Mesozoic deposits are common but less relevant regarding their size and gold content. These hydrothermal ore deposits are genetically associated with subduction related Andean arc magmatism. Due to its relationship with episodic magmatism migrating eastward, there is a tendency for the deposits to be in distinct, north-south trending, belts with a progressive west to east decrease in mineralization age. After analysing 82 cases in total, main gold concentration can be assigned to high-sulfidation epithermal and porphyry type deposits. Low-sulfidation epithermal, IOCG and mesothermal type appears as less relevant. Gold bearing copper deposits constitute an important part of Chile’s total gold production. Both IOCG type but especially porphyry copper deposits are and will remain as a substantial source to supplement the future output of the gold in the country. The 82 deposits with their tonnage and grade studied, represent a total gold content of 11,662 t equivalent to 375 Moz, excluding past production for those exploited. A number of probable gold bearing base metals high tonnage deposits (IOCG and porphyry copper) do not include their gold content in public format, hence the number delivered could be estimated conservative. Methodical geochronological, ore types and zonation studies are required to better appreciate this metallogenic setting widening current understanding and future exploration results.

对智利金矿和含金贱金属矿床的回顾表明，至少存在六种不同类型的矿床，大部分形成于新生代，中新世占主导地位。中生代矿床是常见的，但与它们的大小和含金量不太相关。这些热液矿床与俯冲相关的安第斯弧岩浆作用有关。由于其与幕式岩浆东移的关系，矿床呈明显的南北走向，成矿时代由西向东递进。通过对82个案例的分析，认为金矿主要富集于高硫化浅成热液型和斑岩型矿床。低硫化浅成热液类型、IOCG类型和中温类型的相关性较小。含金铜矿是智利黄金总产量的重要组成部分。无论是IOCG类型的铜矿，尤其是斑岩型铜矿，都是并将继续作为补充该国未来黄金产量的重要来源。根据所研究的82个矿床的吨位和品位，总含金量为11,662吨，相当于375亿盎司，不包括已开采矿床的过去产量。许多可能含金的基本金属高吨位矿床(IOCG和斑岩铜)没有公开其含金量，因此交付的数量可能是保守估计。需要有系统的地质年代学、矿石类型和分带研究，以更好地认识这一成矿环境，扩大目前的认识和未来的勘探成果。

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引用次数: 1

Mid-Cenozoic SHRIMP U-Pb detrital zircon ages from metasedimentary rocks in the North Patagonian Andes of Aysén, Chile 智利ays<s:1>北巴塔哥尼亚安第斯山脉变质沉积岩中新生代SHRIMP U-Pb碎屑锆石

IF 0.9 4区地球科学 Q1 Earth and Planetary Sciences

Andean Geology

Pub Date : 2021-01-29 DOI: 10.5027/ANDGEOV48N1-3282

P. Quezada, F. Hervé, Mauricio Calderón Nettle, C. Fanning, R. Pankhurst, E. Godoy, O. Urbina, R. Suárez

Previously undated low-grade metamorphic rocks from the Puerto Cisnes-Queulat area (44°30’ S) contain detrital zircons of mid-Oligocene age (ca. 28 Ma). Their outcrops represent the easternmost occurrence of the late Oligocene to early Miocene marine volcano-sedimentary Traiguén Formation; previous correlation with the Paleozoic metamorphic basement of this sector of the North Patagonian Andes is thus refuted. A similar age and provenance were obtained for a paraconglomerate bed of the La Junta Formation ca. 80 km to the north, which is thought to represent a high-energy lateral facies variation of the Traiguén Formation. Miocene plutonic rocks of the North Patagonian Batholith intruded these metasedimentary rocks, generating a contact metamorphic aureole that reaches biotite grade and overprints a previous metamorphic fabric probably formed during closure of the Traiguén Basin. Similar young ages for metamorphic rocks located immediately west of the Liquiñe-Ofqui Fault Zone 300 km north, near Ayacara, suggest a regional pattern of earliest Neogene metamorphism and rapid exhumation in this segment of the Patagonian Andes.

Puerto Cisnes-Queulat地区(44°30′S)的低变质岩中含有中渐新世(约28 Ma)的碎屑锆石。它们的露头代表晚渐新世至早中新世海相火山-沉积特瑞古萨组最东端的产状;因此，先前与北巴塔哥尼亚安第斯山脉这一段古生代变质基底的对比被反驳。在其北部约80 km处的La Junta组副砾岩层也获得了类似的年龄和物源，认为这代表了traigusamn组的一次高能侧向相变化。北巴塔哥尼亚基中新世深成岩侵入了这些变质沉积岩，形成了黑云母级的接触变质光圈，并覆盖了可能在特拉古桑盆地闭合期间形成的变质构造。位于Liquiñe-Ofqui断裂带以西300公里以北的Ayacara附近的变质岩的相似年龄表明，在巴塔哥尼亚安第斯山脉的这一段，最早的新近纪变质作用和快速挖掘的区域模式。

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引用次数: 0

Influencia de cuerpos discordantes de distinta cohesión en la geometría estructural de fajas plegadas y corridas: aproximación sobre la base de un modelamiento analógico 不同内聚不均匀体对弯曲带和带状带结构几何形状的影响:基于模拟建模的方法

IF 0.9 4区地球科学 Q1 Earth and Planetary Sciences

Andean Geology

Pub Date : 2021-01-29 DOI: 10.5027/ANDGEOV48N1-3280

M. Villarroel, Pamela Jara, R. Charrier

Lithological heterogeneities in a rock series deformed by the development of a fold-and-thrust belt (FTB) affects the pattern of the resulting structures. We present a series of analogue experiments to determine the effect caused on the deformation pattern of a FTB by the presence of cohesive bodies, like plutons or basement blocks that oppose greater resistance than the host rocks to contractional deformation. The influence of these bodies on the deformation pattern of the FTB was studied by incorporating discordant bodies with different cohesions within a stratified granular sequence with negligible cohesion. We describe two sets of experiments in which the inserted body presents low (Co1) and high (Co2) cohesion respectively. The experiments show a tendency of the structural pattern to curve around the inserted body and to migrate towards the deformation front or the foreland, even when the cohesive body is not exposed. In the first case (Co1) the thrusts cut across the cohesive body, while in the second one (Co2) the cohesive body is not faulted, but transferred towards the deformation front along a basal detachment. Comparison of these results with natural examples at different scales shows a high degree of coincidence in the structural patterns recognized in both cases. Two of the main characteristics of these patterns are the tendency of the thrust faults traces to avoid the cohesive body and adopt the geometry of its distal edge. In order to explain curvatures in natural structural patterns in fold-and-thrust belts, we suggest consider the presence of unexposed bodies with higher strength than their environment.

褶皱冲断带(FTB)发育所变形的岩石系的岩性非均质性影响其构造样式。我们提出了一系列模拟实验，以确定粘性体(如岩体或基底块体)的存在对FTB变形模式的影响，这些体比宿主岩石对收缩变形的阻力更大。通过将具有不同黏结性的不协调体纳入黏结性可忽略的层状颗粒序列中，研究了这些体对FTB变形模式的影响。我们描述了插入体分别呈现低(Co1)和高(Co2)凝聚力的两组实验。实验结果表明，即使黏结体不暴露，构造模式也有绕嵌体弯曲并向变形前沿或前陆移动的趋势。在第一种情况下(Co1)，逆冲断断了黏结体，而在第二种情况下(Co2)，黏结体没有断裂，而是沿着基底分离向变形前缘转移。将这些结果与不同尺度的自然例子进行比较，发现两种情况下识别的结构模式高度吻合。这些构造模式的两个主要特征是逆冲断层轨迹倾向于避开黏结体，并采用其远缘的几何形状。为了解释褶皱冲断带自然构造模式中的曲率，我们建议考虑强度高于其环境的未暴露体的存在。

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引用次数: 1

Caracterización estructural del sistema de ledges y clavos mineralizados del sector Cachinalito, mina El Guanaco, región de Antofagasta, Chile 智利安托法加斯塔地区米纳·埃尔·瓜纳科（Mina El Guanaco）卡奇纳利托（Cachinalito）矿脉和矿柱系统的结构特征

IF 0.9 4区地球科学 Q1 Earth and Planetary Sciences

Andean Geology

Pub Date : 2021-01-29 DOI: 10.5027/ANDGEOV48N1-3171

S. Jovic, G. Páez, Matías Galina, D. Guido, Conrado Permuy Vidal, Luciano López, Stabro Kasaneva

The high sulfidation epithermal gold deposit El Guanaco is located in the Palaeocene-Lower Eocene metallogenic belt in the Antofagasta Region, northern Chile, 215 km SE of Antofagasta city. The deposit is characterized by a system of sub-parallel ledges made of vuggy silica and quartz enargite veins. In the Cachinalito sector, on the north western side of the ore deposit, the ledges system has a discontinuous linear morphology, with a general ENE-OSO orientation, consisting of many ledges segments that change abruptly in orientation, thickness, length and inclination. Grade analysis distribution, detailed mapping at deposit scale, and identification of individual structures (ledges) shows that one of the key factors in deposit genesis is the structural control. The structural analysis allowed visualizing the different segmentations within a general structure, considering the sizes, horizontal and vertical continuity, degree of connection between ledge segments of different orientations, as well as determining the orientations with greater development of mineralized structures. The distribution of the grades allowed to characterize and identify the ore shoots within the ledges, and to interpret the ascending pathways of the mineralizing fluids by dimensioning and separating the high- and low-grade mineralized sectors. This type of analysis and identification represents an important exploration tool and helps exploration and / or production drilling in this type of deposit.

El Guanaco高硫化超低温热液金矿床位于智利北部安托法加斯塔地区的古新世-下始新世成矿带，距离安托法加斯塔市东南215公里。矿床的特征是由多孔二氧化硅和石英绿柱石脉组成的亚平行岩架系统。在矿床西北侧的Cachinalito区，岩架系统具有不连续的线性形态，具有一般的ENE-OSO方向，由许多岩架段组成，这些岩架段在方向、厚度、长度和倾斜度上突然变化。品位分析分布、矿床规模的详细绘图以及单个结构（岩架）的识别表明，矿床成因的关键因素之一是结构控制。结构分析允许可视化一般结构内的不同分段，考虑尺寸、水平和垂直连续性、不同方向的岩架分段之间的连接程度，以及确定矿化结构更发育的方向。品位的分布可以表征和识别岩架内的矿芽，并通过确定高品位和低品位矿化区段的尺寸和分离来解释矿化流体的上升路径。这种类型的分析和识别是一种重要的勘探工具，有助于在这类矿床中进行勘探和/或生产钻探。

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引用次数: 0