Construction and demonstration of an ore prospecting model for the Lala copper deposit in Huili, Sichuan

doi:10.13745/j.esf.sf.2021.1.29

Abstract

Abstract:

The prediction theory and methodology of ore prospecting were developed from an in-depth study of 129 typical deposits in China. The prediction method was verified to be effective, especially for initial ore prospecting. Using this method, a geological model of ore prospecting can be established by combining the internal (geochemical characteristics of elements) and external (types of geological processes) control factors for mineralization. The main components of the prediction model include the metallogenic geological body, structure and structural plane and the characteristics of the metallogenic process. This paper takes the Lala copper deposit in the Huili area, Sichuan Province, as a typical example to illustrate in detail the application of this method in deep ore prospecting of hydrothermal deposits. The Huili area is located in the western margin of the Yangtze Plate, where the regional metallogenic geological conditions are superior and a series of unique Fe-Cu deposits were formed due to the superposition of multi-period tectonic events. In recent years, great prospecting breakthroughs and progress have been made in the deep and peripheral areas of the Lala copper deposit. In this paper, we determined that the early ore-forming geological body is the ore hosting volcanic rock (albitite of the Hekou Group), and the main metallogenic structural control is the interface between basic (intermediate) volcanic and sedimentary rocks and the possible volcanic vent. In the period of hydrothermal superposition, the metallogenic geological body was speculated to be a deep concealed intrusion, and the metallogenic structural controls are mainly folds, faults and fissures. On the basis of summarizing the mineralization characteristics, a geological model of ore prospecting in the Lala copper deposit was established. Together with the results of geological and geophysical explorations, the southern part of Hongnipo was delineated as the ore prospecting target area where a thick, large orebody was later found by drilling verification, which opened up the regional prospecting space.

Key words: prospecting and prediction model, ore prospecting in exploration area, Huili area of Sichuan Province, Lala copper deposit, prospecting demonstration

CLC Number:

CHEN Hui, LIN Lujun, PANG Zhenshan, CHENG Zhizhong, XUE Jianling, TAO Wen, MA Yixing, GONG Lingming, SHEN Hongtao. Construction and demonstration of an ore prospecting model for the Lala copper deposit in Huili, Sichuan[J]. Earth Science Frontiers, 2021, 28(3): 309-327.

Figures/Tables 17

Fig.1 (A) Geotectonic location of the Lala area (modified after [15]) and (B) geological sketch map of the Lala orefield (modified after [17])

Fig.2 Schematic diagrams of (A) Section VIII of the Luodang district (modified from [22]) and (B) Section-3 of the Hongnipo district (modified from [23]) of the Lala copper mine

Fig.3 Statistics of ore-forming ages for the Kangdian copper belt. Modified after [40,45].

Fig.4 Field photos showing the outcropping characteristics of some orebodies on platforms with different elevations in the Luodang Cu deposit

Fig.5 Characteristics of the metallogenic structural plane of the early period in the Luodang Cu deposit

Fig.6 Structural outline map of the Lala area

Fig.7 Photos showing the secondary metallogenic structural planes of fractures and fissures of the hydrothermal superposition period in the Luodang and Hongnipo Cu deposits

Fig.8 Field photos of ores from the Luodang Cu deposit

Fig.9 Photomicrographs showing the typical ore structures

Fig.10 Photomicrographs of mineral assemblages in different periods and stages of the Luodang Cu deposit

Table 1 Paragenetic sequence of the Luodang Cu deposit

Fig.11 Photomicrographs of altered rocks of the early (A, B) and hydrothermal superposition (C-F) periods A,B—早期蚀变类型;C-F—叠加期蚀变类型。Qz—石英;Cal—方解石;Chl—绿泥石;Mus—白云母;Bt—黑云母;Ab—钠长石;Tur—电气石;Fl—萤石。

Fig.12 Prospecting prediction model of the Lala copper deposit

Fig.13 Local aeromagnetic ΔT plan map of the Lala area. Modified after [61].

Fig.14 Geological section map of the Luodang-Lihong district (a) and the result of resistivity profiling by AMT data inversion (b)

Fig.15 Resistivity profiles AMT-16-08 (a) and AMT-19-1 (b)

Fig.16 Longitudinal profile of the southern Hongnipo peripheral copper deposit

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