GISdevelopment.net ---> AARS ---> ACRS 1990 ---> Poster Session Q

Application of remote sensing to seeking blind ore deposcts in the middle lower reaches of Yangtze River

Chen Yinxiang Xu Yuxian
Center of Remote Sensing in Geology,
Ministry o Geology & Mineral Resources
29 Institute Road, Beijing, China


Abstract
26 remote sensing geological interpretation maps at 1:200,00 scale have been compiled for the ore belt along the Yungtze River in an area of 184,700 km2, and 1:50,000 remote sensing survey has been conducted for the geological structures in nearly 10,000 km2 of the orefiled and mining area in Southeastern Hubei; Ruichang, Jiujiang; Zongyang, Lujiang; Ma'anshan; Ning-Zhen and Suzhou where ore is concentrated. Based on the processing and interpretation of the images of TM, MSS an SPOT as well as the color IR air photos, and the integration of geological factor in ore formation and also,. The structures and textures f the magmatic rocks that control the ore deposit have been made known. In the mean time a series of ore deposit models have been reconstructed; 74 new sites have been predicted as favourable section for ore formation, target areas for ore seeking, and ore deposit surrounding the mining area. In addition, remote sensing geological technique series has been established as an approach looking for blind ore deposits, and the theoretical model of deep source magmatic thermo-dynamics has been developed for ore prediction.

With systematic remote sensing geological studies and geological interpretation of ore deposit, the original geological maps have been revised a complemented. Lots of information has been obtained regarding ore deep-seated magmatic structures, which would hardly have been revealed through ground investigations. Moreover, 3166 ring (arc) - shaped structures have been discovered, and nearly 500 sites have been identified as centers of magmtic activity with metallogenic significance, deep petrogenetic and metallo genetic passageway's mall blind rock bodies (stocks), subsurface volcanic organisation and subsurface pump explosion structures- all useful geological information for finding blind ore deposits. Special attention has been given to the scientific and technological problems a follows :


Fig.1 Cycle structure & ore Deposit Distribution at Tonglin Metallogenic Area

The analysis of upper and lower boundaries of magmatic rocks an deep geological structures leading to understanding of the background for roe formation.
Among the various factors determining the formation of the ore deposit, it is believed that magmatic thermo-dynamic motion s the major one, according to our careful remote sensing geological studies. Traditionally, the srufce shallow hard curst has been considered to be the mainforce layer in geological structure formation by various geological structure specialists who believe its folding, faulting, uplifting, expansion and interformational sliding act as a force and create space for magmatic intrusion. As a matter of fact, however, the magmatic melting mass that accounts for 98% in volume from lithosphere to mantle possesses predominant material and thermal energy. It is the magmatic melting mass that supports the thin and fragile crust and with its rising and local penetrating intensive vortex flows, disturbs the movement of the crystalline basement and consolidated magmatic rocks, governs the subsequent sedimentary volcanic formations and controls the fluctuations of the crust, depressions, fold sand faults. Obviously, magmatic bodies should be the leading active force, the essence, while the surface shallow crust is merely superficial expression, passive, reformed and responsive. This is one of the significant understandings obtained as a result of this research project. Centers of magmatic activity have been identified in southeaster Hubei; Jiujiang; Anqing; Luzong; Tongling; Ma'anshan; Liyang; Jurong; Taihu; suzhou and Shanghai, where regional structures and ore deposits are exactly controlled by these lithospheric ring structure as shown in Fig.1 where the ore deposit and the magmatic rocks in southeastern Hubei distribute in ring-shape as a whole.


Fig.2 Suzhu Cycle STructure and Anshan Subvolcanic Organization


Fig.3 Metallogenic Pattern by Deep Source Thermo-dynamics

On the other hand, several blind magmatic bodies of second, third and fourth classes have been inferred on the basis of surface shallow geological structures, such as Dayehu rock dome, as well as rock base, magmatic flat, magmatic peak and magmatic pillar (pipe) shown in fig. 2. Most of them have already been confirmed by airborne magnetic survey and historical earthquake activity, magmatic bodies of various classes undergo tacking evolution along their own passageways constantly and with specific regulation.

The results of structural interpretation have revealed intensive pneumatic explosion and impact expansion in magmatic intrusion zones. Deep high-energy intrusions and shallow low-temperature low-energy mixed magmatic layers can be clearly distinguished with the characteristics form of the magmatic rock. Deep section analysis, make along the upper boundary of the high energy magmatic rock with remote sensing and geophysical data, has shown that the major ore forming locations coincide with the protruding ends on the magmatic boundary whose structure, in addition, also controls the evolution of the crystalline basement, sedimentary - volcanic basin, magmatic intrusion-volcanic dome and tectonic block for a long period of time, representing the in-depth thermal background for the ore formation.

Reconstruction of new models for the ore deposit series based on deep magmatic thermo-dynamic metallogenesis theory.
It is obvious that recent geological survey and mineral exploration will not be conducted until the mineral deposit formation models have been established on the basis of sufficient geology and exploration data, mining records, mineral deposit studies and large quantities of new geology and mineral deposit information. Among them, the comprehensive introduction of remote sensing data, geochemical and geophysical data is remarkably helpful. It is with this understanding that a careful integration analysis has been made for the ore deposits and ore locations in the middle lower reaches of Yangtze river, based on remote sensing information related tot eh large number of orebelts, orefellds, ore-districts and ore deposits in this region combined with present geological, mining, geophysical and geochemical data. The result has shown that here exist ore deposit of large size, high grade and rich in useful components in this region. Most of them are ore liquid hydrothermal filling deposits, i.e. deposits of deep magma pump origin.

These deposits attribute their formation to the deep hear sudden concentration, pneumatic transportation, penetration and impact subsurface expansion and fissure space expansion within the petrogenetic passageways of the magma. They are characterized by : a deep ore-rich magmatic heat root, i.e. a magmatic thermal chamber (store), a relatively fixed petrogenetic and metallogenetic passageway, a group of pipe-like magmatic soil-liquid-gas carriers which emit upward flows intruding, along the nearly vertical linear space, form deep lithosphere and even upper mantle into the surface or subsurface of the crust. These are just what we have located : round-shaped structure, small deep rock body, volcanic passage, small subsurface explosion dome, magmatic peak stock, pipe, thorn and thermal impact pipe, with a diameter less than 5 km.


Fig. 4 Cycle Structrue & Ore Deposit Distribution in Nanjing-Zhenjiang Area, Jiangsu

They are located in the centers of large magmatic protrusions (pillars) as well as certain parts of the peripheric futl zones as shown in Fig.4along such vertical metallogenetic passageways magma encouraged by the decrease gradient of temperature and pressure, open its way in the ore-storing space, resulting in metallognetic series with horizontal and vertical subzones. And such metallogenetic series is represented in different depth by as shown in Fig 5, magmatic segregation type, porphyry type, vienlet impegnation type, ore-liquid filling type, hydrothermal type, layer-following or layer penetration vein type, volcanic gailquid type, contact metasomatic type, volcano sedimentary type, sedimentary type, thermal concentration type and secondary concentration type. These types are in sequential transition while skarn, as a special type, cannot form ore alone (Fig 6). These cadied haws on a stick deposits some times may differ in mineral content, but in the other time they may have the same minerals. Such kind of high temperature high-energy metallogenesis or catagensie has no rigid requirement and selection for ore source formation. Since the extraction of ore material takes place I a very deep and huge magmatic stove, the very high thermal energy alone is capable of making rich ore-liquid from the magmatic complex with the value approximate to Clerk. In addition, this kind of metalogensie, mainly in the form of deep ore-liquid injection, has no special requirement for the country rock as the outflow, emitted by the ore carrier, can crate space on its own, and it has no strict requirement for consolidated surface shallow crust. Therefore, it is an independent high energy system with extremely strong intrinsic structure and geometry, quite different from the concept proposed by traditional geology and multi-compoent blind ore deposites. This kind of high thermal energy metallogenesis is very powerful, not only controls the formation of mineral deposits, but catastaphe. It is for this reason that this theory is referred to as marshal law of geology, or arbitrary decision-making model. This theoretical model enjoy high capability of prediction and economic benefits by rapid inference and high efficiency. Metallogenetic thermo-dynamic passageways of its kind has proved to be stable since Indo-China and Yanshan movements, acting as successive movement during 100,000,000 years.

Someof the thermal structures worked until Cenozoic, and even today, geological catastrophes and other natural disasters are excised and controlled by thermo-dynamics, such as Liyang earthquakes in 1979, South Yellow Sea-Shanghai earthquake in 1982, Changshu earthquake in May 1990, Taihu floods and migration of Yangtze River mouth. The metallognetic series, however, requires careful analysis because of the repeated stacking ore formation and destructive impact along the ore-forming passageway. It is believed that the metallogenetic model produced by remote sensing geology is suitable not only for the middle-lower reaches of Yangtze River, but also for other regions. For the convenience of application, a comprehensive geological model has been established (see fig.6), which represents ore deposits of the closed type central metallogenetic passage.

Remote Sensing studies or Ore field structure for build ore deposits.
As mentioned above, ore-formation is chiefly determined by thermo-dynamic structural conditions. This makes it possible to find theoretical basis and new direction for the application of remote sensing techniques to seeking blind ore deposits. It has been concluded with the study of remote sensing images and IR color airphotos in particular as well as with the repeated 3D analysis of the structure from orefield, from plan to section and from ore deposit to the surrounding area, that one of the significant approaches in seeking mineral deposits, particularly the blind ones, is to study orefield structure at various scales and scales and large scale, with the help of remotely sensed information. Remote sensing technology can provide large quantities of orefield structure information. Remote sensing technology can provide large quantities of orefield structure information with high sensibility, which would hardly be obtained through ground observations or even drillings. Unlike traditional methods, termo-dynamic metal.

logenetic model places its emphasis on the top of the ore-forming rock's pipe or round the pillar head of ore-carrying rock body. There exist in the surface shallow layers of the crust numerous stocks, old and new, stacked and reformed, almost covering the middle-upper part of the lithosphere in the form of "coral" or "bamboo forest structure". In vegetation has been made mostly round the rock pillars consist of favourable for ore formation. A single rock pillar consists of heat source dynamic section, root section, neck pipe section, top shoulder section umbrella-shaped expansion tectonic field, surrounding structure strain field and gas liquid heat source dispersion halo. Most of the meallogenetic pipes stull remains emitting thermal material gas-liquid seepage, often causing earthquakes, intensive pneumatic explosion and various slight material spills, slight metamorphism and geological ecological anomalies, and even meteorological and atmospheric disasters. The rising rock pipe accompanies by intensive impact explosion and gas-liquid dispersion, would take the form of fluid movement rather than simple solid intrusion. Inside the pipe, there appear remarkable ring-like rocks and tectonic trap structures; outside the pipe-mushroom-shaped regular tectonic deformation space with the passage as its axis. The most active part seems to be the pipe-like boundary on the fringe of the pipe, referred to as major fringe faulting impact, heat pressure high metamorphic plane (zone). This is in fact a tough shear zone transformed into a tension - fractured zone on cooling of the pipe, which serves as a major passage for late stage pathogenesis and metallogenesis. It is an ore-conducting structure in the depth and an important ore-liquid filling structure in its shallow part. And this is just the circular structure indicated by remote sensing geology, which is parallel to the major fringe fault. Some additional circular structure planes can often be seen inside and outside the rock body, which bear, to different extent, major fringe fault with ore-forming significance, particularly in the top shoulder part of the rock pipe. The space reached by its radial fault system as well as the outside enclosed plane area important indicators as well as the outside enclosed plane are important indicators of the upper rock pillar's shape and the status of intrusive dynamics. The radial faults are mainly f tension, nature and they can not only conduct but also bear pres, particularly favourable for ore formation when intersecting the circular faults. The third group is tangent fault system. In that case the rise and intrusion of the rock pillar bears spinning character, which leads to the formation of tangent fault system outside with the spinning of the rock pillar, a pair of radial faults usually become O-shaped structure due to penetration and mislocation. The structure on both sides of the O-shaped fault are usually symmetric. To rock pillar before Indo-China movement carries more than two groups of

O-shaped faults, each of whom represents a geological period's thermal event. In the top shoulder part of the roc pillar there formed an umbrella-like intensive faulting deformation space with a complex upthursted fold (geocycnclinal type) fault, a magmatic intrusion zone a volcanic eruption zone, and an intensive thermo metamorphic zone. On the top of the pipe there is and intensive pneumatic explosion cap acting as an excellent zone. On the top of the pipe there is of the pipe while not fully consolidate, carries an impact emission spot, usually and ore pillar and complex ore pipe. Remarkable and sensitive reflection of these zones can be found is surface shallow crust. The fringe fault zone may be a circular sedimentary depression zone, or slicification, alteration zone, fracture zone. The top and upper part of the rock pipe are covered with or shown as round domes, protrusions or basins, with tectonic slopes or vertical compensation subsidence zones in the periphery of the circular pipe. These surface shallow peripheric structures are important indicators of the shape in depth and thermo-dynamic intensity of the rock pipe. All this very weak information regarding geomorphology, Quaternary geology,, tectonics and even landscape cannot be sensing fully recognized without remote sensing methods. To summarize, the application of remote sensing techniques to the study of orefied structures based on deep thermo-dynamic theory is supposed to predict blind ore deposits by using various weak structural information, combined with mineral deposit exploration and mining data to analyze the umbrella like expansion and impact explosion structures in periphery and top shoulder part of the rock pipe at large scales for prediction of blind ore deposits. The tip of the pipe might be buried less than 20km in depth, but 5000m and less appears to be most preferable. The integration of geophysical data including magnetic field, gravity, sounding and biogechemical field plus necessary sampling might be essential in studying orefield structures and blind magmatic body structure.

Prediction of blind mineral deposits


Fig.6 Subvolocanic pnumetic Type Ore Deposit Pattern
Fig.7 Prognoace Map of Tongguanshan Cu-Au Orefield

New developments have been achieved in both theory and methodology for prediction of blind mineral deposits, particularly for the large rich ones of economic and technological interest as well as mineral deposits in the vicinity of mines. Both theory and methods have been tested in analyzing the known mineral deposits. On the basis of the geometry law of the deep thermo dynamic metalloginesis theory, it has been found that exploration of many known orefields was disturbed and limited by nonmetallogenetic indices or empiricism. The exploration was often ended only when part of the Orefield structure or part of mineral deposits (bodies, layers) has been made been identified, leaving behind lots of loopholes in theory. Our theoretical model ha been made up for mineral deposits which might have been ignored. Take Majiashan pyrite deposit as example. It was confirmed, based on our structural analysis, that this Orefield is an anticlinal space


Fig.8 Prognosis Map of Pb-Zn-Ag Deposit, Suzhou

Controlled deposit supported by three blind rock pillars. However, the completed exploration ignored this major ore-controlling background, and the result was that exploration stopped right after just less than half ore bodies has been discovered. Owing to our prediction, the prospect was enlarged more than twice. Another example is Tonglin copper deposit. Upto now, merely less than one third of the Orefield has been detached, but our prediction has enlarged the prospect more than three times, and new mineral deposits discovered in recent years has confirmed our prediction.. half completed exploration of this kind seems to be common in the vicinity of mines, and in explored areas. Prediction has been made in new regions. With the symmetry of our thermo-dynamic metallogenesis theory, sister deposits have been inferred. Matching the known large deposits in size and environment. This theory has been confirmed by the recent discovery of some large and super-large mineral deposits. The second Tieshan Orefield has been predicted on the northwestern fringe of the Tieshan rock pillar. Also another group of orefield have been predicted in the favorable section of the major fringe fault zone and the inner circular fringe fault (Fig. 8). Geogoical data have confirmed that the predicted Orefield prove to reliable, for aeromagnetic survey has shown weak anomalies, and ground mineralizations and small ore location have been found, and metallogenetic alteration zone shave proved to be in continual sequence. Once geophysical techniques and drilling are supplied, it would be possible to find large copper, lead, zink or other mineral deposits. The petrogenetic and metallognetic passageways and ore-conducting and ore containing circular fractured planes are joint points of connection and stacking of deep source magma, thermo-dynamics and tectonic metallogensis. Also, there are the major geometric aspects of prediction with very high potential. They were used in this research and proved remarkably effective in interpreting many blind orefields, ore nodes and ore deposits. The ore-seeking indices used traditionally could hardly be evaluated interms of correctness and therefore, prove to be ineffective. They have been reviewed withthermo-dynamic metallogenesis theory by their location in the thermo-dynamic metallogenetic structural field, instead of by their size and intensity. It is understood that evaluation of rooted indices and introduction of remote sensing data are important development of mineral deposit prediction, as shown in fig 7,8 and 9.

Methodological and technological series of Remote Sensing geology in finding blind mineral deposits.
The study of blind mineral deposits, involving a wide range of geological theories and geological surrey and exploration techniques, is a complex process of information collecting, synthesizing and re-understanding that requreis careful planning, organizing and studying in terms of systematic engineering. Remote sensing geology, as a subsystem, should be brought to fully play in close coordination with other subjects.
  1. Working steps of Remote sensing Geology Subsystem in Seeking Blind Mineral Deposits.

    1:200,000 thematic mapping for mineral deposit and geology: including image processing, fully interpretating and information collection. Make deep structural geology interpretation sections with an emphasis on magmatic rocks upper. Boundary and small deep rock pipe structures for the of identification of magmatic activity and small deep rock evolution and small metallogenetic rock pipes. And finally, locate favourable positions for metallgenesis, in combination with regional geophysical, geochemical and deep drilling data.

    1:10,000-50,000 orefield structure study: based on 1:200,000 map, make an overall orefiled structure analysis of the periphery of the metallogenetic rock pipe, in combination with exploration of mining area, mining and geophysical, geochemical data; predict target areas and sites; makes Orefield structure sections and large scale mineral deposit prediction maps, and design geophysics, geochemistry and geological drilling.

    Tracing study in testing the mineral deposits predicted: Revise, in combination with ground geological observations, sampling, geophysical and geochemical survey drilling and, the proposed scheme and put forward testing requirement for further exploration. Well geophysics, subsurface geophysics and source geophysics and geochemical data should be fully relief upon. Adjust the testing scheme and summarize the theory and methods.

    Special study of remote sensing techniques: Including enhancement of information related tot eh blind mineral deposits; development of correlation information; improvement of airborne remote sensing techniques; reference to various kinds of information; collection of metallogenetic alteration and weak tectonic information; improvement of ore-seeking theory and methods and case summary.

  2. Remote sensing should be done in Advance Remote sensing:

    data must be well studied and developed by remote sensing, geophysical, geochemical and mineral deposit specialists before any planning o blind deposit exploration could be performed. Any new information, new idea and new direction thus obtained will be used to work out a new exploration scheme, to predict concrete target areas and target will be used to work out a new exploration scheme, to predict concrete larger lieved that this would guarantee the first effect in any region and in any case. Any delay or hesitation might make remote sensing less than half effective. Unfortunately, it was already too late. If it has been considered at the beginning of the next research, 4 testing and study projects will be proposed, and the result will be must better.

  3. Relatively perfect prediction and instruction depends on persistent systematic remote sensing study.

    Indoor and outdoor investigations of the whole process and necessary tracing observation are very important. Some of the complete remote sensing geological predictions for metallogenesis lack careful investigation and geological data. "Wild Cat" prediction of its kind is by no means scientific and serious. It is necessary to introduce objective responsibility regulations and position responsibility regulation into the systematic engineering of geological work, so as to ensure the best result it eh whole system.

  4. The Remote sensing geological techniques used for seeking blind Mineral deposits are in urgent need for improvement.

    Present airborne and space remote sensing techniques suffer low spectrum resolution, low space resolution and small number of spectrum bands. Many of them have lost their value for mineral exploration. The things mentioned above are expected to be improved in order to meet the large scale (1:2000-5000) blind ore body exploration and high sensitivity requirements, such as thermal structure, infrared, microwave, readioactive survey and high sensitive requirements, such as thermal structure, infrared, microware, radioactive survey on the deep passage, combined with necessary airborne, ground and subsurface geophysical and geochemical exploration. Some of the ore fields need various kinds of airborne remote sensing techniques for seeking blind mineral deposits, under the support of specialists and new information.

  5. Testing Verification and Elose Co-ordination should be strengthened.

    Without geological survey and exploration including necessary geophysical and geochemical methods, the correctness of prediction theory and approaches could not be verified. A prediction scheme will be well grounded only when it is supported by geological, geophysical and geochemical work. First of all, the predict must submit a concrete testing scheme which should be approved by relevant specialists, one could not be done without the other. There were examples, in which drilling holes were wrong only because the predictor did not participate, and the mistake was corrected with the instruction of the predictor.

    To summarize, the application for remote sensing geology to seeking blind mineral deposis at middle and lower reaches of Yangtze River has already attained certain results in geology and mineral deposits, with some breakthroughs in theory and techniques.
References
  1. Chen Yinxiang (1976) Thermodynamic Tectonic Blocks and Their Significance.

  2. Bureau of Geology and Mineral Resoruces, Jiangsu Province (1984) Historyof Regional Geology and Mienral Deposits in Jiangsu Provicne and Shanghai Urban Districts.

  3. Bureau of geology and mineral resources, Anhui Province 919840 History of Regional Geology and Mineral Resources in Anhui Province.

  4. Bureau of Geology and Mineral Resources, Jaingxi Province (1984) History of Regional Geology and Mineral Resources in Jiangxi Province.

  5. Zhao Penda el al (1987) Mineral Deposit Exploration and Evaluation Criteria.