Microtextural analysis of a glacially ‘deformed’ bedrock: implications for inheritance of preferred clast orientations in diamictons

Although analysis of clast macrofabrics has been used to differentiate between different types of glacial diamictons and to determine palaeo‐ice flow directions, no account appears to have been made of preferred clast orientations inherited from the parental source material. Clast macrofabrics in tills are typically interpreted as having developed in response to an imposed subglacial deformation and as such provide a link between the sedimentary record and glacier dynamics. They rely on the assumption that any preferred clast orientation is a result of deformation/flow. The results of the micromorphological study of the Langholm Till exposed at North Corbelly near Dumfries (southwestern Scotland) clearly demonstrate that bedrock structure can influence clast orientation (macrofabric) within diamictons. In the lower part of the till, the orientation of elongate clasts preserves the geometry of the tectonic cleavage present within the underlying bedrock. The intensity of this steeply inclined, ‘inherited’ clast fabric decreases upward through the till, to be replaced by a more complex pattern of successive generations of clast microfabrics developed in response to deformation/flow. These results indicate potential limitations of applying clast macrofabric or microfabric analysis in isolation to establish till genesis or palaeo ice‐flow directions. Consequently, due account should be made of other glacial palaeo‐environmental and ice flow indicators, as well as rockhead depth and morphology in relation to the selection of fabric measurements sites. © British Geological Survey/Natural Environment Research Council copyright 2007. Reproduced with the permission of BGS/NERC. Published by John Wiley & Sons, Ltd.     

Limestone pseudoconglomerates in the Late Cambrian Gushan and Chaomidian Formations (Shandong Province, China): soft-sediment deformation induced by storm-wave loading

This paper focuses on the formative processes of limestone pseudoconglomerates in the Gushan and Chaomidian Formations (Late Cambrian) of the North China Platform, Shandong Province, China. The Gushan and Chaomidian Formations consist mainly of limestone and shale (marlstone) interlayers, wackestone to packstone, grainstone and microbialite as well as numerous limestone conglomerates. Seventy‐three beds of limestone pseudoconglomerate in the Gushan and Chaomidian Formations were analysed based on clast and matrix compositions, internal fabric, sedimentary structures and bed geometry. These pseudoconglomerates are characterized by oligomictic to polymictic limestone clasts of various shapes (i.e. flat to undulatory disc, blade and sheet), marlstone and/or grainstone matrix and various internal fabrics (i.e. intact, thrusted, edgewise and disorganized), as well as transitional boundaries. Limestone pseudoconglomerates formed as a result of soft‐sediment deformation of carbonate and argillaceous interlayers at a shallow burial depth. Differential early cementation of carbonate and argillaceous sediments provided the requisite conditions for the formation of pseudoconglomerates. Initial deformation (i.e. burial fragmentation, liquefaction and injection) and subsequent mobilization and disruption of fragmented clasts are two important processes for the formation of pseudoconglomerates. Burial fragmentation resulted from mechanical rupture of cohesive carbonate mud, whereas subsequent mobilization of fragmented clasts was due to the injection of fluid materials (liquefied carbonate sand and water‐saturated argillaceous mud) under increased stress. Storm‐wave loading was the most probable deformation mechanism, as an external triggering force. Subsequent re‐orientation and rounding of clasts were probably prolonged under normal compactional stress. Eventually, disrupted clasts, along with matrix materials, were transformed into pseudoconglomerates by progressive lithification. Soft‐sediment deformation is prevalent in alternate layers of limestone and mud(marl)stone and/or grainstone, regardless of their depositional environments.     

Glacigenic clast fabrics: genetic fingerprint or wishful thinking?

The interpretation of glacigenic diamictons is a subjective process, for which quantitative support is frequently sought from parameters such as clast shape and fabric. It has been widely suggested that different glacigenic diamicton facies possess distinct clast‐fabric signatures. This paper examines this concept using a data set of 111 clast fabrics, and a synthesis of published results. Eigenvalues are calculated and compared for a variety sedimentary facies. It is concluded that clast fabric alone is not able to discriminate between different glacigenic facies, and it is argued that clast fabric offers little quantitative support in the interpretation of glacigenic sediments. It is suggested, therefore, that although clast fabric may continue to have a role as an indicator of relative strain at specific sites, its use in the discrimination of glacigenic facies is limited. Consequently, we should be much more selective in undertaking such analyses in the future. Copyright © 1999 John Wiley & Sons, Ltd.     

The statistics of counting clasts in rudites: a review, with examples from the upper Palaeogene of southern California, USA

The relative proportions of gravel sized particles of different lithology in rudaceous sedimentary rocks are generally determined in the field by clast counting. Clast counts are usually carried out qualitatively in order to assess sedimentary provenance. However, a review of the statistical aspects of clast counting suggests that this technique also can be applied quantitatively, and to investigate a variety of other objectives during basin analysis. Geographical and stratigraphical changes in the relative proportions of clasts can be quantified statistically and used to characterize sediment dispersal patterns in space and time, respectively. Statistical comparisons between clast assemblages can be used as a tool to match up rock units. This approach may help to constrain tectonic or suspect-terrane models, or to document sediment recycling. Both counting and sampling errors contribute to the total probable error of a clast count. Sampling error results from the uneven distribution of clasts in outcrop, perhaps caused by selective sorting. Counting error arises from a count of some number less than the total number of clasts in the population. Sampling and counting errors can be minimized by counting in closely spaced subsets, and by counting a total of at least 400 clasts, respectively. Thus, a useful procedure is to count four closely spaced subsets of 100 each, and combine the results for a total of 400. Point counting should not be used because differences in particle size produce biased results. A better method is to count all clasts above some minimum size within a specified area of outcrop. Analysis of upper Palaeogene non-marine conglomerates composing part of the Sespe Formation in California, using confidence intervals, hypothesis testing, analysis of variance, ratio analysis and varietal studies, demonstrates that useful statistics can be derived by counting clasts.     

Comparative study of striations and basal till clast fabrics, Malpeque—Bedeque region, Prince Edward Island, Canada

Coastal erosion has resulted in exposure of a succession of basal till deposits and striation localities along the Malpeque and Bedeque Bays, PEI, Canada, permitting repetitive determinations of clast fabrics and investigation of recently exhumed striations. Striations indicate initial eastward ice flow, followed by a second glacial event with flow towards the south and southwest from the Gulf of St. Lawrence. The degree of local inconsistency and the variations with striation assemblages indicate that the orientations of individual striations cannot be regarded as 'absolute' indicators of ice flow directions. Diamictons identified as basal tills using sedimentological criteria have clast fabrics typical of basal till deposition. Local deviations of fabric trend within individual outcrops are common. A comparative analysis of the data obtained from striation and clast fabric orientations indicates that the ice flow directions independently suggested by each are in general agreement. Differences are present between the orientations of striations and clast fabrics at individual sites. The orientations of the fabrics lie within 20° of the modal striation orientations in only 28% of the cases, and the median deviation between the suggested ice flow directions was 29°. In 40%, of the cases, the azimuth deviation between the two methods exceeded 40°, and the maximum deviation recorded was 84°. At many sites, the deviations are so severe as to potentially result in the misinterpretation of the modal ice flow direction, based on the use of either striation orientation or clast fabric in isolation. Variations in glacial flow can readily produce striations and clast fabrics which record different phases of glacial activity associated with the same glacial event at an individual site.     

Strain memory of 2D and 3D rigid inclusion populations in viscous flows — What is clast SPO telling us?

We model the development of shape preferred orientation (SPO) of a large population of two- and three-dimensional (2D and 3D) rigid clasts suspended in a linear viscous matrix deformed by superposed steady and continuously non-steady plane strain flows to investigate the sensitivity of clasts to changing boundary conditions during a single or superposed deformation events. Resultant clast SPOs are compared to one developed by an identical initial population that experienced a steady flow history of constant kinematic vorticity and reached an identical finite strain state, allowing examination of SPO sensitivity to deformation path. Rotation paths of individual triaxial inclusions are complex, even for steady plane strain flow histories. It has been suggested that the 3D nature of the system renders predictions based on 2D models inadequate for applied clast-based kinematic vorticity gauges. We demonstrate that for a large population of clasts, simplification to a 2D model does provide a good approximation to the SPO predicted by full 3D analysis for steady and non-steady plane strain deformation paths. Predictions of shape fabric development from 2D models are not only qualitatively similar to the more complex 3D analysis, but they display the same limitations of techniques based on clast SPO commonly used as a quantitative kinematic vorticity gauge. Our model results from steady, superposed, and non-steady flow histories with a significant pure shearing component at a wide range of finite strain resemble predictions for an identical initial population that experienced a single steady simple shearing deformation. We conclude that individual 2D and 3D clasts respond instantaneously to changes in boundary conditions, however, in aggregate, the SPO of a population of rigid inclusions does not reflect the late-stage kinematics of deformation, nor is it an indicator of the unique ‘mean’ kinematic vorticity experienced by a deformed rock volume.     

初始组构各向异性对砂土力学特性及临界状态的影响

采用离散元方法,利用半径扩展法和重力沉积法分别生成具有初始各向同性和各向异性内结构的试样,并开展三轴不排水压缩和拉伸试验,研究不同制样方法产生的初始各向异性对砂土宏微观力学特性及其临界状态的影响。运用组构张量对砂土的各向异性进行量化,分析不同初始组构各向异性对组构张量演化的影响并确定了组构张量的临界值。试验结果表明：初始组构各向异性对试样的剪胀性有重要影响,由于受重力影响形成初始各向异性,其各向异性程度越大、组构方向与加载方向越一致,剪胀性越显著;初始组构各向异性对试样的临界状态没有影响,砂土的组构张量具有唯一的临界状态值。     

Structures and textures in till indicating subglacial deposition

Five structural and textural features are discussed: (1) small lenses of sorted material, (2) smudges, (3) small-scale deformations of till matrix and smudges by clasts, (4) clasts consistently striated, and (5) clasts with stoss-and-lee sides. Analyses suggest that these features may be produced by subglacial processes acting in the ice-bed interface. Long axes of small sand lenses and smudges as well as the striation on the upper surface of scattered clasts in lodgement till have a strong preferred orientation in good agreement with the glacier flow direction as indicated by clast fabrics, bedrock striation, and surface fluting of ground moraine. When in traction against the till bed, clasts may plough up till banks. Clasts with stoss-and-lee sides development were also very distinctly oriented as their stoss sides faced significantly up-glacier.
It is concluded (1) that each of the five features discussed is useful as a criterion for subglacial deposition by lodgement, (2) that they indicate important differential movement along the ice-bed interface and therefore suggest a temperate regime in this part of the glacier during the till deposition, (3) that very few orientation measurements of one or more of these features signify the ice movement direction; i.e. a time-saving method to find the paleoflow direction of Pleistocene glaciers, and (4) that taken together with till preconsolidation, mechanical composition, and clast fabric, they may support each other and give good indications of the genesis of Pleistocene tills.     

Diamictic sediments within high Arctic lake sediment cores: evidence for lake ice rafting along the lateral glacial margin

Sediment cores from six small lake basins in the Canadian high Arctic reveal a gravel‐rich (≤30% by weight) to gravel‐poor (≥2%) diamict facies underlying massive, post‐glacial, clayey silt. Ten other lakes contain a second diamict facies within what are interpreted to be glaciolacustrine sedimentary assemblages. The sedimentology, clast fabrics and fossil remains (diatoms, ostracodes and chironomid head capsules) within both diamict facies suggest that these deposits are not tills. Clast fabrics yielded low S₁ (0·41–0·57) and high S₃ (0·09–0·22) eigenvalues, placing them within the range of ice‐rafted diamictons and glacigenic sediment flows. The high percentage of clast dip angles >45° (15–61%), random clast azimuth and lower diamict contacts conformable to underlying current‐bedded sediment favours an origin as a rain‐out or settling deposit. Samples of the matrix and scrapings of clasts from the diamicts revealed a diatom assemblage dominated by littoral and planktonic forms, such as are found in the littoral regions of the lakes today. This contrasts sharply with the assemblages within the overlying clayey silt, in which benthic forms predominate. Clasts are thus interpreted to have been rafted from the littoral areas of the lake. The process proposed to explain this is rafting by the lake ice cover in a glacial‐marginal environment. Early season meltwater, impounded along the lateral margin of retreating cold‐based glaciers, would buoyantly lift the lake ice cover and any adfrozen lake sediment. Higher lake levels and increased areal extent of seasonal freeze‐on between the lake ice cover and the lake bed would allow the redeposition of littoral sediments to the benthic regions through greater lateral shifting of the ice cover as it broke up. Incision by meltwater streams into the lateral glacial margins would later isolate the lake, allowing seasonal warming of lake water, enough to support the growth and maturation of the ostracode and chironomid species found as fossils within the diamicts.     

The Kaidun chondrite breccia: Petrology, oxygen isotopes, and trace element abundances

Oxygen isotope and trace element data for 13 samples of the Kaidun chondritic breccia reaffirm the complex polymict nature of this unique meteorite. Bulk Kaidun samples most closely resemble CR chondrites, but the matrix is CI-like. Two separated clasts are CR-like but have some properties that resemble CM, two clasts are enstatite chondrites (one EL and one EH), one clast is an aubrite-like metal-rich impact melt, and one clast is a unique layered olivine-bearing pyroxenite with the isotopic composition of an aubrite. Yet, although each clast resembles a known meteorite group, all deviate in some respect from the norms for those groups. Collectively, Kaidun has sampled materials not yet represented in the world meteorite collections and which greatly extend the definitions of known meteorite groups. Phyllosilicates in Kaidun span a very wide range in composition and vary from clast to clast, suggesting that the aqueous alteration experienced by the clasts predated assembly of the Kaidun parent body.     

Chemical and physical responses to deformation in micaceous quartzites from the Tauern Window, Eastern Alps

Micaceous quartzites from a subvertical shear zone in the Tauern Window contain abundant quartz clasts derived from dismembered quartz‐tourmaline veins. Bulk plane strain deformation affected these rocks at amphibolite facies conditions. Shape changes suggest net shortening of the clasts by 11–64%, with a mean value of 35%. Quartz within the clasts accommodated this strain largely via dislocation creep processes. On the high‐stress flanks of the clasts, however, quartz was removed via solution mass transfer (pressure solution) processes; the resulting change in bulk composition allowed growth of porphyroblastic staurolite + chlorite ± kyanite on the clast flanks. Matrix SiO₂ contents decrease from c. 83 wt% away from the clasts to 49–58% in the selvages on the clast flanks. The chemical changes are consistent with c. 70% volume loss in the high‐stress zones. Calculated shortening values within the clast flanks are similar to the volume‐loss estimates, and are greatly in excess of the shortening values calculated from the clasts themselves. Flow laws for dislocation creep versus pressure solution imply large strain‐rate gradients and/or differential stress gradients between the matrix and the clast selvages. In a rock containing a large proportion of semirigid clasts, weakening within the clast flanks could dominate rock rheology. In our samples, however, weakening within the selvages was self limiting: (1) growth of strong staurolite porphyroblasts in the selvages protected remaining quartz from dissolution; and (2) overall flattening of the quartz clasts probably decreased the resolved shear stress on the flanks to values near those of the matrix, which would have reduced the driving force for solution‐transfer creep. Extreme chemical changes nonetheless occurred over short distances. The necessity of maintaining strain compatibility may lead to significant localized dissolution in rocks containing rheologic heterogeneities, and overall weakening of the rocks may result. Solution‐transfer creep may be a major process whereby weakening and strain localization occur during deep‐crustal metamorphism of polymineralic rocks.     

Sand intraclasts within a diamicton mélange,southern Niagara Peninsula,Ontario, Canada

Sand intraclasts found within diamicton units along the north shore of Lake Erie in the Mohawk Bay area of the Niagara Peninsula would appear to be part of a ‘block-in-matrix’ mélange. The intraclasts are undeformed and many exhibit primary bedding structures. Numerous intraclasts have been rotated and/or tilted and are, in general, subrounded in outline. Examination of the surrounding diamicton reveals that the diamicton clast fabrics exhibit a wide scatter and are not characteristic of any known till clast fabric. Around each intraclast exists an aureole of brecciated diamicton. Other evidence in the form of macro- and microshear structures, and banding within the diamicton indicate that the diamicton has been subject to high strain. Interpretation of the sand intraclasts seems to be intrinsically linked to the origin of the diamicton and together linked to the origin of the mélange. Various hypotheses are suggested separately for the sand intraclasts, diamicton and mélange. A subglacial deformable bed hypothesis is advanced as the most acceptable explanation for the complete sediment sequence in which diamicton and frozen sand intraclasts, the latter mobilised from the substrate, are moved as a mélange below an active fast-moving ice mass. Several implications from this study emerge with regard to glacial sedimentology and stratigraphic interpretations.     

Argon 40-argon 39 chronology of lithic clasts from the Kapoeta howardite

⁴⁰Ar-³⁹Ar age spectra have been measured on plagioclase separates from three basaltic clasts (A, B, C), a pyroxene separate from clast B, and a total sample of a fourth basaltic clast (ρ) from the Kapoeta achondritic meteorite. The Ar data show that three of the four clasts crystallized ≥4.5 AE ago. Xe measurements indicate all four formed within a 0.1 AE period (Huneke, et al., 1977, Lunar Science VIII, pp. 484–486). Three clasts have suffered various degrees of ⁴⁰Ar loss since that time. The times of ⁴⁰Ar degassing do not cluster about a single time analogous to the lunar cataclysm. The survival of ≥4.5 AE ages contrasts with the general absence of ages ≥4.0 AE on the moon.The Ar retention age of clast B of ≥4.57 AE is atypically older than the Rb-Sr age of 3.6 AE (Papanastassiouet al., 1974, Lunar Science V, p. 583). The 3.5 AE Ar age of clast A is distinctly younger than the Rb-Sr age of 3.9 AE (Papanastassiou et al., 1974). The K-Ar and Rb-Sr systems are clearly not equivalent dating techniques in these instances.The combined evidence of Ar, Xe and Rb-Sr studies suggests the period of volcanism on the Kapoeta parent planet was restricted to the first ~0.2 AE of solar system history. The subsequent thermal metamorphic histories recorded in each of the four clasts after formation are distinctly different. The clasts must have existed as independent fragments at least as recently as 3.5 AE ago. The cosmic ray exposure ages of all the four clasts are similar (~ 3 Myr), and are not significantly different from that of the bulk meteorite. The clasts spent essentially all of the time prior to the formation of Kapoeta at depths greater than a few meters.     

Anisotropy of magnetic susceptibility and rock magnetic applications in the Deccan volcanic province based on some case studies

Anisotropy of Magnetic Susceptibility (AMS) as a tool has been explored here to investigate the nature of petrofabrics in Deccan Volcanic Province (DVP) of west-central Indian region by representative sampling in typical pahoehoe and rubbly pahoehoe lava flows, dykes within flows, shear zone and the impact crater units. The rock magnetic analysis indicate varying degree of concentration of titanomagnetite compositions dominated by multi domain (MD) to pseudo single domain (PSD) grains favoring shape anisotropy of minerals that form primary fabrics. The pahoehoe type lava flows shows planar oblate fabrics without any preferred orientation of principle susceptibility axis (K₁) depicting crystal settling (of magnetic grains) as chief mechanism of fabric development. The rubbly pahoehoe type lava flow exhibit prolate fabrics with well clustered maximum susceptibility axis within horizontal to sub-horizontal planes depicting their response to viscosity shear. The dykes show well clustered K₁ parallel to it’s plane locked during rapid contractional cooling. The sampling at Lonar impact crater was unable to trace any clear fabric due to impact/shock induced deformation and rather preserve the primary fabrics. Further, the shear zone depict random fabrics demanding more detailed and systematic sampling in both the cases. The present investigation infer that the magnetic mineralogy and magnetic fabric variations in the DVP are controlled by the flow mechanism and style of cooling that is characteristic of the given flow unit or dyke and any secondary or superimposed fabric needs to be examined by critical sampling strategy. While more detailed attempts are required to establish the AMS as a tool to record various aspects including the flow dynamics and rate of effusion in the vast terrain of DVP; the present approach is useful to characterize and correlate the lava flow units and dyke occurrences.     

Salt weathering in dual-porosity building dolostones

The influence of rock fabric on physical weathering due to the salt crystallization of selected brecciated dolostones is discussed. These dual-porosity dolostones are representative of heterogeneous and anisotropic building rocks, and present highly complex and heterogeneous rock fabric features. The pore structure of the matrix and clasts is described in terms of porosity and pore size distribution, whereas the relative strength for each textural component is assessed using the Knoop hardness test. The whole characterisation process was carried out using the same samples as those used in the standard salt durability test (EN-12370), including connected porosity, the water saturation coefficient, fissure density, compressional wave velocity and waveform energy.

Results show the most important rock fabric elements to be considered are the matrix and clast properties and the nature of fissures. Firstly, a relatively weak matrix was the focus of major granular disintegration as it presents high porosity, low pore radius and reduced strength. Secondly, narrow micro-fissures appear to be important in the decay process due to the effectiveness of crystallization pressure generated by salt growth. On the contrary, macro-fissures do not contribute greatly to rock decay since they act as sinks to consume the high supersaturations caused by growth of large crystals. Additionally, an analysis of stress generated by crystallization was carried out based on the general situation of a lenticular crystal geometry. Finally, the relationships between whole petrophysical properties and durability were established using a principal component analysis. This analysis has clearly established that the durability of rocks affected by salt crystallization mechanisms diminishes in weaker and anisotropic rocks with high porosity and fissure density.     

Fabric characteristics of subaerial slope deposits

The clast fabrics of certain types of terrestrial slope deposits are reviewed and compared, including the deposits of rockfalls, solifluction, debris flows, dry grain flows, frost-coated clast flows and run-off. The analysis is based on modern deposits in active environments. The study shows that fabric characteristics allow discrimination between ‘collective’and individual movement of rock particles. The individual particle movement generally results in a random clast orientation, whereas the processes of ‘collective’movement typically create distinct preferred orientations. The highest fabric strengths together with low values of spherical variance are found in solifluction deposits. A survey of Pleistocene slope deposits indicates, however, that clast fabric has to be used with caution in the identification of past slope dynamics, because significant post-depositional changes may occur during ageing and burial of deposits. The diagnostic significance of fabric characteristics may also be low due to the overlap of the statistical values that typify different processes.     

Strength anisotropy of granular material consisting of perfectly round particles

The strength anisotropy of granular materials deposited under gravity has mostly been attributed to elongated particles' tendency to align long axes along the bedding plane direction. However, recent experiments on near‐spherical glass beads, for which preferred particle alignment is inapplicable, have exhibited surprisingly strong strength anisotropy. This study tests the hypothesis that certain amount of fabric anisotropy caused by the anisotropic stress during deposition under gravity can be locked in a circular‐particle deposit. Such locked‐in fabric anisotropy can withstand isotropic consolidation and leads to significant strength anisotropy. 2D discrete element method simulations of direct shear tests on circular‐particle deposits are conducted in this study, allowing for the monitoring of both stress and fabric. Simulations on both monodispersed and polydispersed circular‐particle samples generated under downward gravitational acceleration exhibit clear anisotropy in shear strength, thereby proving the hypothesis. When using contact normal‐based and void‐based fabric tensors to quantify fabric anisotropy in the material, we find that the intensity of anisotropy is discernible but low prior to shearing and is dependent on the consolidation process and the dispersity of the sample. The fact that samples with very low anisotropy intensity measurements still exhibit fairly strong strength anisotropy suggests that current typical contact normal‐based and void‐based second‐order fabric tensor formulations may not be very effective in reflecting the anisotropic peak shear strength of granular materials. Copyright © 2017 John Wiley & Sons, Ltd.     

川西北磁组构演化及其揭示的应变特征

对龙门山褶皱冲断带北段前锋带至四川盆地边缘的川西北地区进行了磁组构研究.在江油和广元之间,沿着垂直于龙门山构造走向的4条采样路线,在18个采样点钻取了173个定向样品,样品采自侏罗纪和白垩纪砂岩及粉砂质泥岩.综合分析表明川西北磁组构反映的是新生代的变形,并在研究区域内总结出了3类磁组构:沉积磁组构、初始变形磁组构和铅笔状磁组构.除沉积磁组构之外的所有采样点样品的K1优势方向都是NE-SW向,说明研究区域的最大主压应力方向为NW-SE向,主要来源于龙门山褶皱冲断带.在垂直于龙门山褶皱冲断带构造走向上,从四川盆地到龙门山前锋,磁组构由沉积磁组构逐渐变为初始变形磁组构,直至铅笔状磁组构,说明盆地内部应变十分微弱,靠近造山带应变逐渐增强,且侏罗纪、白垩纪以来研究区的构造变形主要集中在造山带边缘或者还未传递到盆地内部.     

胶东大磨曲家金矿床岩石磁组构、构造变形与金矿化

在胶东地区招远-平度断裂带上的大磨曲家金矿区选取了典型的构造区域进行岩石磁组构研究。沿着断裂带在不同构造部位的36个采样点钻取了112个定向岩心样品,所有样品均沿勘探线布置。磁组构研究显示,研究区以弱磁性岩石为主,总体上,胶东群变质岩的磁化率值较高,而玲珑黑云母花岗岩的磁化率值较低,尤以碎裂程度高的强蚀变岩的磁化率值最低;磁化率各向异性方位主要为NE向挤压,磁组构所指示的构造应力场与大磨曲家矿区的区域挤压应力方向是相同的;对具不同程度矿化的81线的Au含量与80线磁组构各向异性度(P值)进行对比研究发现,P值与金品位呈负相关关系;弱矿化糜棱岩中的金矿化在磁面理发育的岩石中较为发育,成矿晚期,Au元素含量随着岩石磁性的减弱而增加,特别是在强应变后弛豫阶段矿液充填于相对张性的石英脉中Au含量最高。