阅读说明：本技术 一种运用锆石结构判别锆石成因类型的方法 (Method for discriminating origin type of zircon by using zircon structure ) 是由 王生云 范洪海 王凤岗 陈金勇 吴玉 朱泉龙 王伟 宋振涛 于 2020-12-25 设计创作，主要内容包括：本发明属于锆石类型鉴定技术领域,具体涉及一种运用锆石结构判别锆石成因类型的方法。采集岩矿石样品；选出非磁性重矿物锆石,制备分析样品靶；采集锆石样品背散射电子图像和阴极发光电子图像；将采集的锆石背散射电子图像和阴极发光电子图像与典型的锆石进行晶体形貌与内部结构特征比对,从而判别锆石成因类型。该方法涵盖面广、时效性好、适用性强、准确性高。判别锆石成因类型,从而对获得的锆石U-Pb年龄作出科学、合理的解释具有十分重要的意义,推广应用前景广阔。(The invention belongs to the technical field of zircon type identification, and particularly relates to a method for judging a zircon cause type by using a zircon structure. Collecting a rock ore sample; selecting non-magnetic heavy mineral zircon, and preparing an analysis sample target; collecting a back scattering electron image and a cathode luminescence electron image of a zircon sample; and comparing the acquired zircon back scattering electron image and the acquired cathodoluminescence electron image with the crystal morphology and the internal structure characteristics of typical zircon, thereby judging the cause type of the zircon. The method has the advantages of wide coverage, good timeliness, strong applicability and high accuracy. The method has very important significance for scientifically and reasonably explaining the U-Pb age of the obtained zircon and has wide popularization and application prospects.)

1. A method for distinguishing the cause type of zircon by using a zircon structure is characterized by comprising the following steps:

1) collecting a rock ore sample;

2) selecting non-magnetic heavy mineral zircon, and preparing an analysis sample target;

3) collecting a back scattering electron image and a cathode luminescence electron image of a zircon sample;

4) and comparing the acquired zircon back scattering electron image and the acquired cathodoluminescence electron image with the crystal morphology and the internal structure characteristics of typical zircon, thereby judging the cause type of the zircon.

2. The method of using a zircon structure for determining the type of cause of a zircon according to claim 1, wherein: in the step 1), the content of granite zircon is high, about 1-5 kg of samples are collected, the content of basic rock zircon is low, and 15-50 kg of samples are collected.

3. The method of using a zircon structure for determining the type of cause of a zircon according to claim 1, wherein: in the step 2), the collected rock ore sample is mechanically crushed to 50-80 meshes, and the non-magnetic heavy mineral zircon is separated by utilizing gravity separation and magnetic separation technologies.

4. The method of using a zircon structure for determining the type of cause of a zircon according to claim 1, wherein: in the step 2), zircon particles are stuck on the double-sided adhesive, fixed by colorless and transparent epoxy resin, and the surface is polished after curing.

5. The method of using a zircon structure for determining the type of cause of a zircon according to claim 1, wherein: the step 3) is specifically

3.1) carrying out zircon back scattering electrophotography and cathodoluminescence electrophotography on the prepared zircon analysis sample target;

3.2) putting a zircon sample to be tested into a test bench of the high-vacuum scanning electron microscope;

and 3.3) utilizing a high vacuum scanning electron microscope to converge electron beams as an excitation source to bombard the surface of the zircon sample to generate an electron signal, and collecting a corresponding electronic image.

6. The method of using a zircon structure for determining the type of cause of a zircon according to claim 5, wherein: the electronic signal is secondary electrons, backscattered electrons or cathode fluorescence, and the electronic image is a secondary electronic image, a backscattered image or a cathodoluminescence image.

7. The method of using a zircon structure for determining the type of cause of a zircon according to claim 5, wherein: the high vacuum scanning electron microscope is used for carrying out high vacuum mode secondary electron image and back scattering electron image observation and low vacuum mode back scattering electron image observation.

8. The method of using a zircon structure for determining the type of cause of a zircon according to claim 5, wherein: the high vacuum scanning electron microscope is used for performing qualitative and semi-quantitative analysis on energy spectrums of all elements except hydrogen, helium and lithium.

9. The method of using a zircon structure for determining the type of cause of a zircon according to claim 5, wherein: the detector of the high vacuum scanning electron microscope is a secondary electron detector or a semiconductor detector.

Technical Field

The invention belongs to the technical field of zircon type identification, and particularly relates to a method for judging a zircon cause type by using a zircon structure.

Background

Because the zircon is stable in physical and chemical properties, low in common lead content, rich in uranium and thorium, low in ion diffusion rate and high in sealing temperature (>800 ℃), the zircon becomes the most ideal target for U-Pb fixed years. In addition, zircon is commonly found in various types of rock, and zircon samples are easily sorted. Thus, zircon has become a powerful tool in geological research, and the zircon U-Pb method has been the most common method for geologists to discuss the occurrence time of geological events. With the development of scientific technology, researchers found that different zircon grains and different regions of the same zircon grain in the same geologic body had different causes. Therefore, the cause type of the zircon is judged, and the obtained zircon U-Pb age is scientifically and reasonably explained, so that the method is very important for understanding the geological action process and promoting the development of earth science.

Zircon belongs to the tetragonal system, is an island silicate, and the combination characteristics of regular and variable crystal faces make it a typical morphological standard mineral. The size of the zircon crystals depends on the zirconium content of the initial magma, and the crystal morphology of zircon is determined by the physicochemical conditions under which it crystallizes and the internal structure of the crystals. The basic morphological characteristics of zircon can reveal its history in the rock and, based thereon, reasonably account for the age values obtained, and zircon morphological studies are of considerable interest to researchers. Researchers have determined the type of cause of zircon by studying its morphology using methods such as zircon length, width, aspect ratio and frequency profile, zircon cylinder, cone and elongation index, flatness, elongation, cylinder and cone index, and the like. The above method for studying zircon morphology requires a lot of time and effort for researchers, occupies a long time of instruments and equipment, and is not easy to be mastered by primary researchers, without detailed observation under the mirror and a lot of statistics and analysis. With the development of science and technology, by utilizing a zircon Back Scattering Electron (BSE) image and a cathodoluminescence electron (CL) image, the internal structure of zircon can be effectively disclosed so as to judge the cause type of zircon, errors caused by artificial statistics are avoided, and the method has the characteristics of economy, simplicity and convenience in operation, short determination time and the like. Therefore, it is very meaningful and effective to identify the cause of zircon using zircon backscattered electron (BSE) images and cathodoluminescent electron (CL) images.

Disclosure of Invention

The invention aims to provide a method for distinguishing the cause type of zircon by using a zircon structure, which can distinguish the cause type of zircon simply, conveniently, quickly, economically and quickly.

The technical scheme of the invention is as follows:

a method for distinguishing the cause type of zircon by using a zircon structure comprises the following steps:

1) collecting a rock ore sample;

2) selecting non-magnetic heavy mineral zircon, and preparing an analysis sample target;

3) collecting a back scattering electron image and a cathode luminescence electron image of a zircon sample;

4) and comparing the acquired zircon back scattering electron image and the acquired cathodoluminescence electron image with the crystal morphology and the internal structure characteristics of typical zircon, thereby judging the cause type of the zircon.

In the step 1), the content of granite zircon is high, about 1-5 kg of samples are collected, the content of basic rock zircon is low, and 15-50 kg of samples are collected.

In the step 2), the collected rock ore sample is mechanically crushed to 50-80 meshes, and the non-magnetic heavy mineral zircon is separated by utilizing gravity separation and magnetic separation technologies.

In the step 2), zircon particles are stuck on the double-sided adhesive, fixed by colorless and transparent epoxy resin, and the surface is polished after curing.

The step 3) is specifically

3.1) carrying out zircon back scattering electrophotography and cathodoluminescence electrophotography on the prepared zircon analysis sample target;

3.2) putting a zircon sample to be tested into a test bench of the high-vacuum scanning electron microscope;

and 3.3) utilizing a high vacuum scanning electron microscope to converge electron beams as an excitation source to bombard the surface of the zircon sample to generate an electron signal, and collecting a corresponding electronic image.

The electronic signal is secondary electrons, backscattered electrons or cathode fluorescence, and the electronic image is a secondary electronic image, a backscattered image or a cathodoluminescence image.

The high vacuum scanning electron microscope is used for carrying out high vacuum mode secondary electron image and back scattering electron image observation and low vacuum mode back scattering electron image observation.

The high vacuum scanning electron microscope is used for performing qualitative and semi-quantitative analysis on energy spectrums of all elements except hydrogen, helium and lithium.

The detector of the high vacuum scanning electron microscope is a secondary electron detector or a semiconductor detector.

The invention has the following remarkable effects:

the method for judging the cause type of the zircon by using the zircon structure is designed by the method, the existing high-precision instruments are fully utilized, and the effect of advanced technical means in mineral analysis is fully exerted, so that the method is wide in coverage area, good in timeliness, strong in applicability and high in accuracy. The method has very important significance for scientifically and reasonably explaining the U-Pb age of the obtained zircon and has wide popularization and application prospects.

Due to the fact that the method for comparing the zircon Back Scattering Electron (BSE) image and the cathodoluminescence electron (CL) image designed by the method with the typical zircon BSE image and the CL image of different cause types can simply, quickly and effectively judge the cause types of the zircon, and technical support is provided for understanding the geological action process and promoting the development of earth science.

Drawings

FIG. 1 is a flow chart of a method for determining a cause type of zircon using a zircon structure according to the present invention;

FIG. 2 is a cathodoluminescence image of zircon in granite and bedrock in a region according to an embodiment of the present invention.

Detailed Description

The invention is further illustrated by the accompanying drawings and the detailed description.

As shown in figure 1 of the drawings, in which,

step one, collecting a rock ore sample;

through field geological investigation, rock ore samples needing to be subjected to chronology research are determined and collected. The number of samples was determined according to the rock type. Generally, the content of granite zircon is high, about 1-5 kg of samples are collected, the content of basic rock zircon is low, and 15-50 kg of samples need to be collected.

Step two, sorting zircon, and preparing an analysis sample target;

mechanically crushing the rock ore sample collected in the step one to 50-80 meshes, and separating the non-magnetic heavy mineral zircon by utilizing gravity separation and magnetic separation technologies. Zircon particles (more than 30) are stuck on the double-sided adhesive, fixed by colorless transparent epoxy resin, and the surface is polished after curing.

Collecting a Back Scattered Electron (BSE) image and a cathodoluminescence electron (CL) image of the zircon sample;

and (3) performing zircon Back Scattering Electron (BSE) photography and cathodoluminescence electron (CL) photography on the zircon analysis sample target prepared in the second step by using an instrument such as a scanning electron microscope or an electron probe, and the like, as shown in figure 2.

In particular to

3.1) carrying out zircon Back Scattering Electron (BSE) photography and cathode luminescence electron (CL) photography on the prepared zircon analysis sample target by using a TESCAN scanning electron microscope GAIA 3;

and 3.2) putting a zircon sample to be tested into a test board of the high-vacuum scanning electron microscope according to the operating specification of the scanning electron microscope, and adjusting the focal length according to the relevant operation instructions of the instrument to enable the test sample to be in the optimal position.

The high vacuum scanning electron microscope is mainly used for carrying out high vacuum mode secondary electron image and back scattering electron image observation and low vacuum mode back scattering electron image observation; in addition, qualitative and semi-quantitative analysis of energy spectrums of all elements except hydrogen, helium and lithium can be carried out, and the main technical indexes are as follows:

high vacuum mode resolution: 3.0 nm; low vacuum mode resolution: 4.0 nm; magnification: 5-300000 times; a detector: secondary electron detectors, semiconductor detectors; image types: secondary electronic images, back-scattered images (component images, topological images, stereoscopic images);

and 3.3) bombarding the surface of the zircon sample by using the electron beam converged by the scanning electron microscope as an excitation source to generate various electron signals (such as secondary electrons, backscattered electrons and cathode fluorescence), and collecting corresponding electronic images (secondary electronic images, backscattered images and cathode luminescence images).

And step four, comparing the acquired zircon Back Scattering Electron (BSE) image and cathode luminescence electron (CL) image with the crystal morphology and internal structure characteristics of typical zircon, thereby judging the cause type of the zircon.

And (3) comparing the zircon Back Scattered Electron (BSE) image and the cathodoluminescence electron (CL) image acquired in the step three with the crystal morphology and the internal structure characteristics of typical zircon with different cause types, thereby accurately judging the cause types of the zircon.

The present invention has been described in detail with reference to the drawings and examples, but the present invention is not limited to the examples, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present invention. The prior art can be adopted in the content which is not described in detail in the invention.

The rock magma zircon is generally in a long column shape, most of the rock magma zircon is a self-shaped crystal with a linear growth line, and is usually a simple square bipyramid or a complex square bipyramid, the development of a conical surface and a cylindrical surface is perfect, a rock magma oscillation growth zone or a wide and slow rock magma growth zone which is obvious can be seen on a BSE image and a CL image, generally, the medium-base rock magma zircon usually forms a wider crystallization zone, and the acid rock magma zircon usually forms a narrower rock magma zone; the metamorphic zircon develops multiple crystal faces without the division of conical surfaces and cylindrical surfaces, even if the metamorphic zircon presents long granular shapes, the metamorphic recrystallized zircon usually has more dark inclusion bodies, muddy growth lines and muddy circular kernels on BSE images and CL images, and has complex structure types such as no banding, weak banding, fan-shaped banding, planar banding, cloud banding, spot banding, sponge banding, flowing banding and the like; keatite also forms oscillating annuli or segmental zonations similar to magma zircon, which often exhibit complex secondary internal structures and interpenetrate primary structures, with numerous inclusions of phosphate silicates.