1. Possible types of mineral deposits
1) Hydrothermal type. In the Guizhou region, studying the mineralization conditions of hydrothermal platinum group element deposits has important theoretical and practical significance. The large-scale magmatic activity in Guizhou is not very developed on the surface, and there are relatively few magmatic rocks exposed on the surface, which makes it difficult to find platinum group element deposits. However, Guizhou's hydrothermal deposits, especially epithermal deposits, are very developed, with many types and wide distribution. Minerals such as mercury, antimony, arsenic, and thallium play an important role both at home and abroad. These deposits are mainly distributed in areas far away from the Emeishan basalt outcrop, and have no connection with the Emei mantle plume on the surface. However, metal elements such as Hg, Sb and As are different from ore-forming elements such as Cu, Pb and Zn. They are more mobile and more likely to be transported in the gas phase. Moreover, Hg, As and Sb themselves have the ability to transport other metals. possibility. Therefore, although they are not easy to accumulate and form minerals stably under high temperature conditions, it does not necessarily mean that there is no magmatism in their depths. Hg, Sb, and As can all form platinum group minerals with platinum group elements, such as mercury palladium ore (Polarite, Pd Hg), telluride mercury palladium ore (Pd3Hg Te3), arsenic palladium ore (Arsenopalladinite, Pd8 (As, Sb) 3) , arsenic platinum ore (Pt As2), Emei ore (Os As), hexagonal antimony palladium ore (Sudburyite, Pd Sb), isometric antimony platinum ore (Geversite, Pt Sb2) and other at least 40 kinds of minerals. Therefore, research and exploration of platinum group element mineralization cannot be given up in the mineralization areas of mercury, arsenic, and antimony, which are the dominant minerals in Guizhou.
2) Coal rock type. Coal is an important host rock for PGE. The PGE in coal may be adsorbed after the coal mine is formed, but it may also be enriched during the mineralization process of the coal mine. The enrichment mechanism of PGE in coal is not very clear, but the discovery of PGE in a coal-bearing depression in Russia fully proves that PGE in coal may be very important. Li Shengsheng et al. (2002) have reported the enrichment of PGE in coal in southwestern Guizhou. What is urgently needed to investigate and study is which areas, which era (layer), and which type of coal contain PGE, and where are the coals containing PGE? Whether the spatiotemporal distribution is related to the distribution of Emeishan basalt is meaningful for developing ore prospecting ideas. Natural platinum produced in asphalt has been found in many places in the Cambrian-Ordovician limestone strata and its Precambrian basement strata in the Appalachian orogen at the border of the United States and Canada. Whether PGE is enriched in some oil and gas areas in Guizhou, especially some oil and gas reservoirs (including bitumen) that may have been damaged, is also a new topic.
3) Abnormal sedimentary rock type. Abnormal sedimentary rocks refer to sedimentary rocks formed when the normal deposition process is disturbed by unexpected events. Unexpected events include meteorite impacts, volcanic eruptions and other derived geological processes, such as fumaroles and anoxic events related to submarine volcanic eruptions. Ore-bearing black rock series may belong to this category. Black rock series in many areas of the world have been found to contain platinum group elements. Among them, Russia's Dry Valley Gold-Platinum Group Element Deposit has confirmed that at least 1000t of platinum group elements are present in the black rock series. middle. The widely distributed Cambrian black rock series in Guizhou may also be abnormal sedimentary rocks. The Huangjiawan nickel-molybdenum deposit near Zunyi contains PGE. Regarding the source of the abnormally enriched PGE in the black rock series at the bottom of the Cambrian in Guizhou and other places, Li Shengrong et al. (2000) based on the abundance and ratio of Au, Ag, and PGE in the enriched layer in Hunan and Guizhou, and the correlation of elements, The element distribution model and partitioning model believe that these mineralizing elements are not directly provided by extraterrestrial materials, nor are they deposited from normal seawater, but may be mainly related to the action of seafloor hot water jets, that is, they are extracted from seafloor hot water through deep circulation. It was formed from basic-ultrabasic rock materials in the Wuling Period of the Proterozoic Eon. According to senior engineer Wang Yangeng, alkaline magmatic carbonate was recently discovered in the floor of the ore-bearing black rock series. Therefore, the possibility of magmatic activity providing minerals cannot be ruled out.
2. Possible areas and mineralization ages
The Zunyi Huangjiawan nickel-molybdenum-platinum group element deposit has been confirmed to be formed in the Cambrian and occurs at the bottom of the Cambrian. , belongs to the black shale type nickel-molybdenum-platinum group element deposit. Mao Jingwen et al. (2001) used negative ion thermal surface ionization mass spectrometry to conduct precise Re-Os isotope age measurement on the ore, and obtained the isochron of (541.3±16) Ma (2σ) The age indicates that the Huangjiawan deposit is a component of the Cambrian black shale polymetallic mineralization belt in South China. However, the platinum group element mineralization era in Guizhou is certainly not limited to this. Other possible eras and areas include:
1) Komati rocks have been discovered in the Fanjing Mountain area in northeastern Guizhou, so The existence of Proterozoic komatiite-type platinum group element deposits needs to be investigated. There are still many issues that need to be clarified about the Komati rocks in Mount Fanjing, but the formation of the Dapoling platinum-bearing copper-nickel deposit in the Baotan area of ??northern Guangxi that may be related to the Proterozoic-like komati rocks can be used as a piece of information. . Gao Zhenmin et al. (1998), Li Shengrong et al. (2000), Mao Jingwen et al. (2001), Zhang Guangdi et al. (2002) all proposed that the platinum group elements in the Cambrian black shale may come from the proterozoic Wuling period basic-ultrabasic If this is the view of basic rocks, then are Wuling period basic-ultrabasic rocks themselves containing minerals?
2) The Cambrian black rock series is widely distributed, not limited to Zunyi. The Cambrian near Hunan and other places is also worthy of note. The Early Cambrian black pages in Weng'an, Zhijin and other places are also worth noting. Rocks also contain precious metals (Zhang Aiyun et al., 1987).
3) Various types of hydrothermal platinum-group element deposits may occur in the Emeishan basalt distribution area, including coal-rock type, structurally controlled hydrothermal type, and associated platinum-group elements in basalt-type natural copper deposits. Element deposits, etc.; its mineralization era may extend from the end of the Permian to the Cenozoic. The existence of late tectonic events and related regional thermal convection systems is of key significance to the activation, transfer and mineralization of PGE present in basalt, and must be considered in the process of searching for late hydrothermal platinum group element deposits. More and more studies have shown that the activity of PGE is obvious, and obvious transfer may occur even at low temperatures.
4) The platinum group element deposits associated with epithermal deposits on the periphery of the Emeishan basalt distribution area, including the Carlin-type gold deposits in the Yunnan-Guizhou-Guangxi Golden Triangle, may have been formed in the Mesozoic Era. The author once discussed the origin of the two gold mineralization concentration areas in Jiaodong and Yunnan, Guizhou and Guangxi from the perspective of mantle plumes (Wang Denghong, 1998). At present, it seems that mantle plumes (not just the Emei mantle plume in the Permian) restrict gold deposits. The understanding of the formation of mineralization concentration areas is still not out of date, although the debate on whether the mineralization concentration areas of Carlin-type gold deposits in Nevada, USA are related to hot spots has never stopped. Su Wenchao et al. (2001) used ICP-MS to measure the composition of quartz fluid inclusions at different mineralization stages in the two Carlin-type gold deposits, Lannigou and Yata. The results showed that the contents of Co, Ni, Cu, Pb and Zn were relatively high. , and high contents of Pt were detected in the quartz fluid inclusions in the main mineralization period of these two gold deposits. This discovery not only helps to confirm the view that basic-ultrabasic igneous rocks may be an important source of minerals for Carlin-type gold deposits in southwestern Guizhou, but also provides important information for the search for platinum deposits in Carlin-type gold deposit distribution areas. .
5) Laterite-type gold deposits, weathering-crust-type bauxite and sand-platinum deposits in basalt weathering crust and other unidentified platinum group element deposit types, etc.
3. Influence of post-mineralization structures
Although Guizhou is relatively far away from the Tibetan Plateau, the Cenozoic tectonic movement is still obvious (Qin Shourong et al., 1998). The Cenozoic is not the main period for platinum group element mineralization, but the study of Cenozoic tectonic movements will help develop ore prospecting ideas. According to the author's observation and research, several platinum group element deposits currently known to be related to the dark rock series originating from the Paleozoic Emei mantle plume are mainly distributed in the west and central areas in space, and few have been discovered in the east (but this cannot be ruled out). possibility); it may be basically contemporaneous with the eruption of Emeishan basalt, but its complexity must be taken into consideration.
At present, the author has used the R Oes isotopic dating method to determine the mineralization age of the Baimazhai copper-nickel deposit in Yunnan to be 249 Ma. The exact mineralization age of Jinbaoshan in Yunnan is still unclear, but it may also be the Hercynian period (according to "Yunnan Provincial and Regional Mineral Summary, the K-Ar age of biotite in Jinbaoshan peridotite is 304Ma, and the Rb-Sr age is 322Ma. If this age is indeed and represents the age of rock formation and mineralization, the Jinbaoshan platinum group element deposit may be related to it. The Emei mantle plume active around 250 Ma has no direct connection and is the product of another geological event); and the isotope age of quartz in the Yangliuping hydrothermal copper-nickel-platinum group element ore in Sichuan measured by the 40Ar/39Ar method varies greatly. Large, ranging from 242.59Ma ??to 11.38Ma (Wang Denghong et al., 2003), reflecting the multi-stage influence of post-mineralization structures. This tectonic influence is manifested in the following: ① The Yangliuping mining area is located in the Danba thermal dome area. It is the rising thermal dome structure that lifts the ore-bearing rock mass to the surface (and leads to multiple stages of hydrothermal transformation into mineralization). People can discover it; ② The Jinbaoshan mining area is just cut by the Lishe River in the upper reaches of the Red River. The ore body and ore-bearing rock mass are nearly horizontal, but they happen to be deeply cut by the water system and exposed; ③ The Baimazhai ore-bearing rock mass is It was pushed up due to the strong shearing effect of the Cenozoic. Therefore, if there was no Cenozoic tectonic activity (the types can be different, such as the water system cutting and erosion in Jinbaoshan, the shearing and pushing up of Baimazhai, and the thermal dome uplifting in Yangliuping), these ore bodies would be buried deep underground. Hard to be discovered by people.
According to the idea of ??mantle plume mineralization, platinum group element deposits mainly occur at the tail of the mantle plume rather than at the head (Wang Denghong, 1998). In fact, the basalt or komatiite that corresponds to the head of the mantle plume itself is not the most mineral-rich. High content of PGE may appear in basalt, but no formed deposits have been found so far; high content of PGE often appears in komatiite, but there are not many large ore deposits and rich ore deposits. Due to long-term erosion of the mantle plume in Bushveld, South Africa since the Proterozoic Era, the basalt representing the head product of the mantle plume has been eroded, and the basic-ultrabasic rock complex and a series of basic-ultrabasic rock complexes corresponding to the middle and lower parts of the mantle plume have been eroded. The rock pipe has been eroded and exposed, and chromite layers containing platinum group elements and other types of platinum deposits are also near the surface, making them easy to discover. Therefore, when searching for platinum group element deposits that are genetically related to the Emei mantle plume in the southwestern region, Cenozoic tectonic movements and erosion conditions must be considered.