Gullet Quarry- Igneous Investigation.

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Gullet Quarry- Igneous Investigation.

Investigation.  : To study the igneous intrusions at Gullet Quarry

Aims :

  1. To investigate whether the intrusions are of the same age.
  2. To investigate whether the intrusions are the same type.
  3. To investigate whether they are all from the same magma source.
  4. To determine a sequence of events in the igneous section of the quarry.

Plan :

        To carry out this investigation I will need the following equipment: hand lens, geologists hammer, crystal size card, ruler, tape measure, clinometer, penknife and a streak plate.

        In collecting the data to carry out this investigation I am proposing  all the evidence will be uniform and will conform with the igneous work I have learnt in class. If there are any anomalous results in my data I will do my best to fit the anomalous result into my work.

        The evidence I am looking for is as follows:-

  1. Crystal size. Crystal size is an important variable in determining the origin of the igneous rocks. The crystal size depends on how deep the rock was when it was formed. Finer crystals indicate that the rocks were cooled at a rapid rate i.e. near the surface of the earth. The larger the crystals are the slower the crystals were formed. Larger crystals show that the rocks were formed deep into the earth’s mantle. To investigate crystal size I will need a hand lens, a crystal size card and a ruler. To investigate crystal size I will hold the hand lens about 5cm away from the rock and use the crystal size card to compare the crystal size to the crystal size on the card. Then record the size and then measure the crystal size on the card in millimetres. The variations in crystal size may be due to chilled/ baked margins. The use of millimetres will help to give us a very good degree of accuracy for our results.
  2. Mineral content. The mineral content is identified by looking at a proportion of the intrusion and estimating the percentage of a mineral in that specific section. This will help identify whether there are variations in the type of magma in each intrusion. The identification of this is based on observations although some tests may be hard to carry out in the field. To identify the type of mineral I will use a penknife and coin to test the hardness of the mineral and then compare the result to the scale of hardness.
  3. Presence of baked/chilled margins. This will help determine the nature of the magma and country rock when the intrusion took place.
  4. Type of country rock. If the igneous rocks were intruded at the same time one would presume that the country rock would be of the same type.
  5. Angle of dip of the intrusions. I will do this to see if there are any relations between the intrusions.
  6. Presence of any other geological features. If there is evidence of earth movements ,i.e. faults, in the intrusions this will help me to determine the sequence of events.
  7. Measurements of the intrusions. If there is a correlation between the size of the intrusion and size of crystals then this could render some of the data irrelevant. Most of my findings will be based on crystal size.
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Predictions. 

        I predict that the intrusions were formed at different times and are from  different magma sources.

Safety.

         When I am carrying out this investigation I must remember that the quarry is a potentially dangerous environment. A helmet must be worn at all times during the experiment. When hammering at the rock safety goggles must be worn. The hammering must be kept to a minimum as the hammering could trigger a rock fall.

Analysis.

I studied 4 different sections of ...

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