, ▁dy kes , ▁and ▁s ills ▁covering ▁a ▁pale o - sur face ▁of ▁ 3 ▁× ▁ 1 0 6   km 2 . ▁ ▁Jur ass ic ▁dy kes ▁found ▁in ▁the ▁dy ke ▁sw ar ms ▁are ▁mostly ▁composed ▁of ▁dol er ite , ▁containing ▁clin opy ro x ene , ▁pl agi oc l ase , ▁and ▁ol iv ine . ▁Gra in ▁size ▁is ▁from ▁fine ▁to ▁medium . ▁F resh ▁min eral ▁alter ation ▁has ▁occurred ▁as ▁ser ic ite , ▁ser pent ine , ▁and ▁ch lor ite ▁are ▁found . ▁In ▁Pro ter oz o ic ▁dy kes ▁of ▁the ▁Save - L imp opo ▁dy ke ▁sw arm , ▁Leb om bo ▁dy ke ▁sw arm ▁and ▁Ol if ants ▁River ▁dy ke ▁sw ar ms , ▁gra in ▁size ▁is ▁observed ▁to ▁be ▁co ar ser ▁with ▁absence ▁of ▁ol iv ine . ▁Am ph ib ol ite , ▁ch lor ite , ▁and ▁py rite ▁are ▁found ▁in ▁a ▁significant ▁portion . ▁Min er als ▁in ▁Pro to zo ic ▁rocks ▁are ▁more ▁sever ely ▁alter ed ▁than ▁in ▁Jur ass ic ▁dy kes . ▁ ▁Min eral ogy ▁ ▁The ▁Ok av ango ▁dy ke ▁sw arm ▁is ▁mainly ▁composed ▁of ▁ma fic ▁rocks , ▁namely ▁bas alt , ▁dol er ite , ▁gab bro ▁and ▁ol iv ine - th ole i ites . ▁Min er als ▁include ▁ 3 5 – 4 5 % ▁pl agi oc l