Resistivity Survey of Weathered BasResistivity Survey of Weathered Basalt at Ban Khok Salung Area, Lopbualt at Ban Khok Salung Area, Lopbu

ri, Central Thailandri, Central Thailand

*A.Nochai wong *A.Nochai wong *F.S.Si nghar aj war apan *F.S.Si nghar aj war apan **W.Galong **W.Galong

* Chiang Mai University ** Department of Mineral Resources

TYPE OF ROCKAGE

(million years)

Rhyolite 11-13

Basalt 18

Rhyolite 18-21

Pyroclastic rock and tuff 22

Porphyritic andesite, basaltic

andesite, quartz latite, and

quartz trachyte

22-24

Table 1. Geologic sequence of the Lam Narai Group

(Jungyusuk and Suriyachai, 1987).

Data AquisitionData Aquisition

* * Resistivity Depth sounding Resistivity Depth sounding

* Schlumberger configuration * Schlumberger configuration

H HHH HHHHHHH HHHHHHHHH HHHHHHH * H HHH HHHHHHH HHHHHHHHH HHHHHHH *

1130to m. 1130to m.

Resistivity Sounding Data

3-Layer Resistivity Model

7-Layer Resistivity Model

Resistivity Model Selection

Geologic Model

Data InterpretationData Interpretation

Model Type Layer configuration

Three-LayerModel

1. Overburden2. Weathered basalt(including weathered pyroclastic rock)3. Fresh basalt

Seven-LayerModel

1. Overburden2. Weathered basalt3. Rhyolite (11-13 million years)4. Basalt5. Rhyolite (18-21 million years)6. Pyroclastic rock and tuff7. Porphyritic andesite, basaltic andesite,quartz latite, and quartz trachyte

Table 2. Model Layering

ConclusionConclusion

Target : Weathered Basalt Target : Weathered Basalt

Zone.Zone.Result : Excellent in delineating the base of Result : Excellent in delineating the base of

weathered basalt zone and depth to weathered basalt zone and depth to

basement. basement.

Poor in differentiating between Poor in differentiating between

weathered basalt and weathered weathered basalt and weathered

pyroclastic rocks. pyroclastic rocks.