* Trading volumes in region are moderate
* Saudi's Arabian Pipes soars in heavy trade
* Abu Dhabi's UNB keeps rising on merger speculation
* Dubai Parks dominates trade in Dubai
* Egypt's Asec drops on Q1 loss; parent Qalaa falls
By Andrew Torchia
DUBAI, June 22 (Reuters) - Gulf stock markets were mixed in narrow ranges and moderate volumes on Wednesday, with investors cautious before Britain's European Union referendum. Egypt resumed sliding after it broke major technical support earlier this week.
Saudi Arabia's index dropped 0.3 percent. Some banks were weak, with Saudi Hollandi Bank down 2.8 percent. Saudi Basic Industries, the Gulf's largest listed petrochemical producer, added 0.3 percent as oil prices rose.
Arabian Pipes jumped its 10 percent daily limit for a second straight day in its heaviest trading since early 2005.
In Abu Dhabi, Union National Bank jumped 4.4 percent in a second day of strong gains, after Arqaam Capital said in a note on Tuesday that following the proposed merger between National Bank of Abu Dhabi and First Gulf Bank, "we expect UNB to be next".
It said Abu Dhabi Commercial Bank might offer a substantial premium to UNB shareholders in a merger; ADCB shares rose 2.8 percent on Wednesday. NBAD, which soared earlier this week, rose a further 1.7 percent while FGB fell 1.6 percent. The main Abu Dhabi index edged down 0.1 percent.
Dubai's index climbed 1.0 percent with Dubai Parks and Resorts, the most heavily traded stock, surging 4.1 percent to 1.54 dirhams.
The company is in an uptrend before the opening of its first theme parks later this year in Dubai, but the stock now exceeds the 1.47-dirham median target price of three analysts surveyed by Reuters.
Qatar's index was flat, although Qatar International Islamic Bank added 2.3 percent in unusually heavy trade.
Cairo's main stock index dropped 1.3 percent to 7,156 points. It has been technically bearish since it broke earlier this week below its April and May lows, triggering a head & shoulders pattern pointing down to the 6,700 point area.
Asec Company for Mining sank 2.8 percent after reporting that it swung to a consolidated loss in the first quarter from a year-earlier profit. Its parent company Qalaa Holdings sank 6.3 percent.
* The index fell 0.3 percent to 6,532 points.
* The index rose 1.0 percent to 3,376 points.
* The index edged down 0.1 percent to 4,498 points.
* The index was flat at 9,919 points.
* The index dropped 1.3 percent to 7,156 points.
* The index fell 0.5 percent to 5,409 points.
* The index edged up 0.01 percent to 5,789 points.
* The index ropped 0.3 percent to 1,113 points. (Editing by Larry King) ((firstname.lastname@example.org; +9715 6681 7277; Reuters Messaging: email@example.com))