Geobotanic Remote Sensing for Mo deposit exploration in dinhu Mo ore-field, Guangdong, China
Xu Huocheng, Xu Resong, Lu Huiping, Wu Jin
Institute of New Technology in Geology, ChineseAcademy of Sciences
Xie Yongquan
Zhongshan University
Abstract
As is known, excess Mo in soil would lead to the physiology and ecology variance of plants and their spectrum characteristics change. The authors have studies these variances and carried out a computer manipulation and information collection for the remote sensing information of aerial color infrared, MSS and TM data. The remote sensing data, combined with the spectrum data of plants, are summarized and indicating that it is feasible for using the gobotanary remote sensing to explore hidden deposit into area covered by plants.
Geological Setting
The investigated area is large scalre porphyry Mo deposit, locating at the Tropic of Cancer. It adjaces to the Dinhu Nature Protectorate UNESCO. It occurs at the Huidong-Goyao E-W extent fault and Sihuo-wuchuan NE extent fault. The strata Middle-lower Devonian series siltstone shale and the magmatic rock is plagiclass grano-phorphyry (gp52(3)), which is a SW-NE extend ellipse rock body. The Mo ore-body occurs at the inside and outside contact of the porphyry body. The alteration zones of the country rock from inside to outside are biotite-k-feldparzation (Bi-Or). Quarts-serisitization, where the Mo mineralization took place quarts-pyritizatiion (Q-Py) and chlorite-phyritizatiion (chl-Py) zone. The distribution of Mo content in rock, soil and plants from Mo ore-body and consistent with that in background area. The correlation coefficients between their Mo contents are more than 0.90 (see table 1).
Effect of mo on plant physiology and ecology
The effect of Mo on plant physiology and ecology, especially for leguminous plant is investigated. The former researchers consider that Mo can help plant grow. But our results indicate that different Mo content has different effect on plant physiology and ecology. When Mo content in soil is more than 50ppm, it would poison the plants. The higher Mo content is the more serious the poison degree of plants is. For example in the centre of the ore-body, Mo>1200ppm in the soil, the leguminous plants extincted. The leaves of the chief plants such as Itea chnensis, Rhodomyrtus, D. linear is var. disholoma and so on in ore-field will fade green and become yellow. When the palnts are seriously poisoned, a lot of yellow-brown spots appear on their leaves. The conifor of conferous tree Pinus massoniana turn red or red brown most of leaves become
withered and some brand died. These ecology change result in existing the so called polychrome plant community in this area, i.e. leaves of plants have become green, yellow, brown, red and grey.
Table 1 Mo contents in rock, soil and plants (ppm).
| |
Rock |
BLayer of soil |
02 |
03 |
04 |
05 |
| 2/87 |
11/87 |
2/87 |
11/87 |
2/87 |
11/87 |
2/87 |
11/87 |
| 2 |
1188.81 |
1063.71 |
8.40 |
6.97 |
6.44 |
4.03 |
0.15 |
2.59 |
7.01 |
6.2 |
| 4 |
297.89 |
1159.37 |
2.28 |
7.99 |
7.85 |
10.55 |
|
3.63 |
5.28 |
9.23 |
| 6 |
52.44 |
304.60 |
0.14 |
<0.2 |
2.99 |
1.52 |
|
0.49 |
2.43 |
3.48 |
| 8 |
10.03 |
23.53 |
0.14 |
0.37 |
0.29 |
1.03 |
0.43 |
0.20 |
0.46 |
0.90 |
| 9 |
7.47 |
10.7 |
0.14 |
0.22 |
0.19 |
0.67 |
0.19 |
0.20 |
0.28 |
|
| 10 |
12.73 |
4.64 |
0.29 |
0.44 |
0.14 |
<0.2 |
|
0.30 |
0.14 |
<0.2 |
Note : 02 pinus massoniana 03-Rhodomyrtus tomentosa 04-Itea Chinesis 05-D-var dchotoma.
When Mo content is 5-50 ppm in soil, Mo can help plants grow. The appearance of plant community trends to normal. The growing and development of the leguminous plant is good with green and large and normal flower and fluid. But if Mo is less than 5 ppm in soil, the leguminous plant growing is unhealthy owing to lack of nutritions. Excess Mo content is soil will bring about excess Mo existences in plant. As a result, it effects on the absorption and conveyance of Mg, Mo, Fe, Cu and Zn in plant, resulting inlosing the Fe/Mo, Mg/Mo, Cu/Mo, Zn/Mo and Mn/Mo balance in plants, especially the Mg content obviously reduced, which effects on chlorophyll metabolism and pholosynthesis. The following phenomena took place: chlorophyll content is reduced and the blade calls are destroyed, green leaves turn into yellow, appearing brown-yellows spots, leaf peak withered and become yellow. These plant physiology and ecology change caused by excess Mo leads to the change of the reflective spectrum characteristics of the plants.
